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7Network Working Group                                      R. Droms, Ed.
8Request for Comments: 3315                                         Cisco
9Category: Standards Track                                       J. Bound
10                                                         Hewlett Packard
11                                                                 B. Volz
12                                                                Ericsson
13                                                                T. Lemon
14                                                                 Nominum
15                                                              C. Perkins
16                                                   Nokia Research Center
17                                                               M. Carney
18                                                        Sun Microsystems
19                                                               July 2003
20
21
22         Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
23
24Status of this Memo
25
26   This document specifies an Internet standards track protocol for the
27   Internet community, and requests discussion and suggestions for
28   improvements.  Please refer to the current edition of the "Internet
29   Official Protocol Standards" (STD 1) for the standardization state
30   and status of this protocol.  Distribution of this memo is unlimited.
31
32Copyright Notice
33
34   Copyright (C) The Internet Society (2003).  All Rights Reserved.
35
36Abstract
37
38   The Dynamic Host Configuration Protocol for IPv6 (DHCP) enables DHCP
39   servers to pass configuration parameters such as IPv6 network
40   addresses to IPv6 nodes.  It offers the capability of automatic
41   allocation of reusable network addresses and additional configuration
42   flexibility.  This protocol is a stateful counterpart to "IPv6
43   Stateless Address Autoconfiguration" (RFC 2462), and can be used
44   separately or concurrently with the latter to obtain configuration
45   parameters.
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60RFC 3315                     DHCP for IPv6                     July 2003
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62
63Table of Contents
64
65   1.  Introduction and Overview . . . . . . . . . . . . . . . . . .   5
66       1.1.   Protocols and Addressing . . . . . . . . . . . . . . .   6
67       1.2.   Client-server Exchanges Involving Two Messages . . . .   6
68       1.3.   Client-server Exchanges Involving Four Messages. . . .   7
69   2.  Requirements. . . . . . . . . . . . . . . . . . . . . . . . .   7
70   3.  Background. . . . . . . . . . . . . . . . . . . . . . . . . .   8
71   4.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   8
72       4.1.   IPv6 Terminology . . . . . . . . . . . . . . . . . . .   9
73       4.2.   DHCP Terminology . . . . . . . . . . . . . . . . . . .  10
74   5.  DHCP Constants. . . . . . . . . . . . . . . . . . . . . . . .  12
75       5.1.   Multicast Addresses. . . . . . . . . . . . . . . . . .  13
76       5.2.   UDP Ports. . . . . . . . . . . . . . . . . . . . . . .  13
77       5.3.   DHCP Message Types . . . . . . . . . . . . . . . . . .  13
78       5.4.   Status Codes . . . . . . . . . . . . . . . . . . . . .  15
79       5.5.   Transmission and Retransmission Parameters . . . . . .  16
80       5.6    Representation of time values and "Infinity" as a time
81              value. . . . . . . . . . . . . . . . . . . . . . . . .  16
82   6.  Client/Server Message Formats . . . . . . . . . . . . . . . .  16
83   7.  Relay Agent/Server Message Formats. . . . . . . . . . . . . .  17
84       7.1.   Relay-forward Message. . . . . . . . . . . . . . . . .  18
85       7.2.   Relay-reply Message. . . . . . . . . . . . . . . . . .  19
86   8.  Representation and Use of Domain Names. . . . . . . . . . . .  19
87   9.  DHCP Unique Identifier (DUID) . . . . . . . . . . . . . . . .  19
88       9.1.   DUID Contents. . . . . . . . . . . . . . . . . . . . .  20
89       9.2.   DUID Based on Link-layer Address Plus Time [DUID-LLT].  20
90       9.3.   DUID Assigned by Vendor Based on Enterprise Number
91              [DUID-EN]. . . . . . . . . . . . . . . . . . . . . . .  22
92       9.4.   DUID Based on Link-layer Address [DUID-LL] . . . . . .  22
93   10. Identity Association. . . . . . . . . . . . . . . . . . . . .  23
94   11. Selecting Addresses for Assignment to an IA . . . . . . . . .  24
95   12. Management of Temporary Addresses . . . . . . . . . . . . . .  25
96   13. Transmission of Messages by a Client. . . . . . . . . . . . .  25
97   14. Reliability of Client Initiated Message Exchanges . . . . . .  26
98   15. Message Validation. . . . . . . . . . . . . . . . . . . . . .  27
99       15.1.  Use of Transaction IDs . . . . . . . . . . . . . . . .  28
100       15.2.  Solicit Message. . . . . . . . . . . . . . . . . . . .  28
101       15.3.  Advertise Message. . . . . . . . . . . . . . . . . . .  28
102       15.4.  Request Message. . . . . . . . . . . . . . . . . . . .  29
103       15.5.  Confirm Message. . . . . . . . . . . . . . . . . . . .  29
104       15.6.  Renew Message. . . . . . . . . . . . . . . . . . . . .  29
105       15.7.  Rebind Message . . . . . . . . . . . . . . . . . . . .  29
106       15.8.  Decline Messages . . . . . . . . . . . . . . . . . . .  30
107       15.9.  Release Message. . . . . . . . . . . . . . . . . . . .  30
108       15.10. Reply Message. . . . . . . . . . . . . . . . . . . . .  30
109       15.11. Reconfigure Message. . . . . . . . . . . . . . . . . .  31
110       15.12. Information-request Message. . . . . . . . . . . . . .  31
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118
119       15.13. Relay-forward Message. . . . . . . . . . . . . . . . .  31
120       15.14. Relay-reply Message. . . . . . . . . . . . . . . . . .  31
121   16. Client Source Address and Interface Selection . . . . . . . .  32
122   17. DHCP Server Solicitation. . . . . . . . . . . . . . . . . . .  32
123       17.1.  Client Behavior. . . . . . . . . . . . . . . . . . . .  32
124              17.1.1. Creation of Solicit Messages . . . . . . . . .  32
125              17.1.2. Transmission of Solicit Messages . . . . . . .  33
126              17.1.3. Receipt of Advertise Messages. . . . . . . . .  35
127              17.1.4. Receipt of Reply Message . . . . . . . . . . .  35
128       17.2.  Server Behavior. . . . . . . . . . . . . . . . . . . .  36
129              17.2.1. Receipt of Solicit Messages  . . . . . . . . .  36
130              17.2.2. Creation and Transmission of Advertise Messages 36
131              17.2.3. Creation and Transmission of Reply Messages. .  38
132   18. DHCP Client-Initiated Configuration Exchange. . . . . . . . .  38
133       18.1.  Client Behavior. . . . . . . . . . . . . . . . . . . .  39
134              18.1.1. Creation and Transmission of Request Messages.  39
135              18.1.2. Creation and Transmission of Confirm Messages.  40
136              18.1.3. Creation and Transmission of Renew Messages. .  41
137              18.1.4. Creation and Transmission of Rebind Messages .  43
138              18.1.5. Creation and Transmission of Information-
139                      request Messages  . . .. . . . . . . . . . . .  44
140              18.1.6. Creation and Transmission of Release Messages.  44
141              18.1.7. Creation and Transmission of Decline Messages.  46
142              18.1.8. Receipt of Reply Messages. . . . . . . . . . .  46
143       18.2.  Server Behavior. . . . . . . . . . . . . . . . . . . .  48
144              18.2.1. Receipt of Request Messages. . . . . . . . . .  49
145              18.2.2. Receipt of Confirm Messages. . . . . . . . . .  50
146              18.2.3. Receipt of Renew Messages. . . . . . . . . . .  51
147              18.2.4. Receipt of Rebind Messages . . . . . . . . . .  51
148              18.2.5. Receipt of Information-request Messages. . . .  52
149              18.2.6. Receipt of Release Messages. . . . . . . . . .  53
150              18.2.7. Receipt of Decline Messages. . . . . . . . . .  53
151              18.2.8. Transmission of Reply Messages . . . . . . . .  54
152   19. DHCP Server-Initiated Configuration Exchange. . . . . . . . .  54
153       19.1.  Server Behavior. . . . . . . . . . . . . . . . . . . .  55
154              19.1.1. Creation and Transmission of Reconfigure
155                      Messages . . . . . . . . . . . . . . . . . . .  55
156              19.1.2. Time Out and Retransmission of Reconfigure
157                      Messages . . . . . . . . . . . . . . . . . . .  56
158       19.2.  Receipt of Renew Messages. . . . . . . . . . . . . . .  56
159       19.3.  Receipt of Information-request Messages. . . . . . . .  56
160       19.4.  Client Behavior. . . . . . . . . . . . . . . . . . . .  57
161              19.4.1. Receipt of Reconfigure Messages. . . . . . . .  57
162              19.4.2. Creation and Transmission of Renew Messages. .  58
163              19.4.3. Creation and Transmission of Information-
164                      request Messages . . . . . . . . . . . . . . .  58
165              19.4.4. Time Out and Retransmission of Renew or
166                      Information-request Messages . . . . . . . . .  58
167
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174
175              19.4.5. Receipt of Reply Messages. . . . . . . . . . .  58
176   20. Relay Agent Behavior. . . . . . . . . . . . . . . . . . . . .  58
177       20.1.  Relaying a Client Message or a Relay-forward Message .  59
178              20.1.1. Relaying a Message from a Client . . . . . . .  59
179              20.1.2. Relaying a Message from a Relay Agent. . . . .  59
180       20.2.  Relaying a Relay-reply Message . . . . . . . . . . . .  60
181       20.3.  Construction of Relay-reply Messages . . . . . . . . .  60
182   21. Authentication of DHCP Messages . . . . . . . . . . . . . . .  61
183       21.1.  Security of Messages Sent Between Servers and Relay
184              Agents  . . . . . .  . . . . . . . . . . . . . . . . .  61
185       21.2.  Summary of DHCP Authentication . . . . . . . . . . . .  63
186       21.3.  Replay Detection . . . . . . . . . . . . . . . . . . .  63
187       21.4.  Delayed Authentication Protocol. . . . . . . . . . . .  63
188              21.4.1. Use of the Authentication Option in the Delayed
189                      Authentication Protocol. . . . . . . . . . . .  64
190              21.4.2. Message Validation . . . . . . . . . . . . . .  65
191              21.4.3. Key Utilization  . . . . . . . . . . . . . . .  65
192              21.4.4. Client Considerations for Delayed Authentication
193                      Protocol . . . . . . . . . . . . . . . . . . .  66
194              21.4.5. Server Considerations for Delayed Authentication
195                      Protocol . . . . . . . . . . . . . . . . . . .  67
196       21.5.  Reconfigure Key Authentication Protocol. . . . . . . .  68
197              21.5.1. Use of the Authentication Option in the
198                      Reconfigure Key Authentication Protocol. . . .  69
199              21.5.2. Server considerations for Reconfigure Key
200                      protocol . . . . . . . . . . . . . . . . . . .  69
201              21.5.3. Client considerations for Reconfigure Key
202                      protocol . . . . . . . . . . . . . . . . . . .  70
203   22. DHCP Options. . . . . . . . . . . . . . . . . . . . . . . . .  70
204       22.1.  Format of DHCP Options . . . . . . . . . . . . . . . .  71
205       22.2.  Client Identifier Option . . . . . . . . . . . . . . .  71
206       22.3.  Server Identifier Option . . . . . . . . . . . . . . .  72
207       22.4.  Identity Association for Non-temporary Addresses Option 72
208       22.5.  Identity Association for Temporary Addresses Option. .  75
209       22.6.  IA Address Option. . . . . . . . . . . . . . . . . . .  76
210       22.7.  Option Request Option. . . . . . . . . . . . . . . . .  78
211       22.8.  Preference Option. . . . . . . . . . . . . . . . . . .  79
212       22.9.  Elapsed Time Option. . . . . . . . . . . . . . . . . .  79
213       22.10. Relay Message Option . . . . . . . . . . . . . . . . .  80
214       22.11. Authentication Option. . . . . . . . . . . . . . . . .  81
215       22.12. Server Unicast Option. . . . . . . . . . . . . . . . .  82
216       22.13. Status Code Option . . . . . . . . . . . . . . . . . .  82
217       22.14. Rapid Commit Option. . . . . . . . . . . . . . . . . .  83
218       22.15. User Class Option. . . . . . . . . . . . . . . . . . .  84
219       22.16. Vendor Class Option. . . . . . . . . . . . . . . . . .  85
220       22.17. Vendor-specific Information Option . . . . . . . . . .  86
221       22.18. Interface-Id Option. . . . . . . . . . . . . . . . . .  87
222       22.19. Reconfigure Message Option . . . . . . . . . . . . . .  88
223
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230
231       22.20. Reconfigure Accept Option. . . . . . . . . . . . . . .  89
232   23. Security Considerations . . . . . . . . . . . . . . . . . . .  89
233   24. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  91
234       24.1.  Multicast Addresses. . . . . . . . . . . . . . . . . .  92
235       24.2.  DHCP Message Types . . . . . . . . . . . . . . . . . .  93
236       24.3.  DHCP Options . . . . . . . . . . . . . . . . . . . . .  94
237       24.4.  Status Codes . . . . . . . . . . . . . . . . . . . . .  95
238       24.5.  DUID . . . . . . . . . . . . . . . . . . . . . . . . .  95
239   25. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  95
240   26. References. . . . . . . . . . . . . . . . . . . . . . . . . .  96
241       26.1.  Normative References . . . . . . . . . . . . . . . . .  96
242       26.2.  Informative References . . . . . . . . . . . . . . . .  97
243   A. Appearance of Options in Message Types . . . . . . . . . . . .  98
244   B. Appearance of Options in the Options Field of DHCP Options . .  99
245   Chair's Address . . . . . . . . . . . . . . . . . . . . . . . . .  99
246   Authors' Addresses. . . . . . . . . . . . . . . . . . . . . . . . 100
247   Full Copyright Statement. . . . . . . . . . . . . . . . . . . . . 101
248
2491. Introduction and Overview
250
251   This document describes DHCP for IPv6 (DHCP), a client/server
252   protocol that provides managed configuration of devices.
253
254   DHCP can provide a device with addresses assigned by a DHCP server
255   and other configuration information, which are carried in options.
256   DHCP can be extended through the definition of new options to carry
257   configuration information not specified in this document.
258
259   DHCP is the "stateful address autoconfiguration protocol" and the
260   "stateful autoconfiguration protocol" referred to in "IPv6 Stateless
261   Address Autoconfiguration" [17].
262
263   The operational models and relevant configuration information for
264   DHCPv4 [18][19] and DHCPv6 are sufficiently different that
265   integration between the two services is not included in this
266   document.  If there is sufficient interest and demand, integration
267   can be specified in a document that extends DHCPv6 to carry IPv4
268   addresses and configuration information.
269
270   The remainder of this introduction summarizes DHCP, explaining the
271   message exchange mechanisms and example message flows.  The message
272   flows in sections 1.2 and 1.3 are intended as illustrations of DHCP
273   operation rather than an exhaustive list of all possible
274   client-server interactions.  Sections 17, 18, and 19 explain client
275   and server operation in detail.
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277
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2871.1. Protocols and Addressing
288
289   Clients and servers exchange DHCP messages using UDP [15].  The
290   client uses a link-local address or addresses determined through
291   other mechanisms for transmitting and receiving DHCP messages.
292
293   DHCP servers receive messages from clients using a reserved,
294   link-scoped multicast address.  A DHCP client transmits most messages
295   to this reserved multicast address, so that the client need not be
296   configured with the address or addresses of DHCP servers.
297
298   To allow a DHCP client to send a message to a DHCP server that is not
299   attached to the same link, a DHCP relay agent on the client's link
300   will relay messages between the client and server.  The operation of
301   the relay agent is transparent to the client and the discussion of
302   message exchanges in the remainder of this section will omit the
303   description of message relaying by relay agents.
304
305   Once the client has determined the address of a server, it may under
306   some circumstances send messages directly to the server using
307   unicast.
308
3091.2. Client-server Exchanges Involving Two Messages
310
311   When a DHCP client does not need to have a DHCP server assign it IP
312   addresses, the client can obtain configuration information such as a
313   list of available DNS servers [20] or NTP servers [21] through a
314   single message and reply exchanged with a DHCP server.  To obtain
315   configuration information the client first sends an
316   Information-Request message to the All_DHCP_Relay_Agents_and_Servers
317   multicast address.  Servers respond with a Reply message containing
318   the configuration information for the client.
319
320   This message exchange assumes that the client requires only
321   configuration information and does not require the assignment of any
322   IPv6 addresses.
323
324   When a server has IPv6 addresses and other configuration information
325   committed to a client, the client and server may be able to complete
326   the exchange using only two messages, instead of four messages as
327   described in the next section.  In this case, the client sends a
328   Solicit message to the All_DHCP_Relay_Agents_and_Servers requesting
329   the assignment of addresses and other configuration information.
330   This message includes an indication that the client is willing to
331   accept an immediate Reply message from the server.  The server that
332   is willing to commit the assignment of addresses to the client
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334
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342
343   immediately responds with a Reply message.  The configuration
344   information and the addresses in the Reply message are then
345   immediately available for use by the client.
346
347   Each address assigned to the client has associated preferred and
348   valid lifetimes specified by the server.  To request an extension of
349   the lifetimes assigned to an address, the client sends a Renew
350   message to the server.  The server sends a Reply message to the
351   client with the new lifetimes, allowing the client to continue to use
352   the address without interruption.
353
3541.3. Client-server Exchanges Involving Four Messages
355
356   To request the assignment of one or more IPv6 addresses, a client
357   first locates a DHCP server and then requests the assignment of
358   addresses and other configuration information from the server.  The
359   client sends a Solicit message to the
360   All_DHCP_Relay_Agents_and_Servers address to find available DHCP
361   servers.  Any server that can meet the client's requirements responds
362   with an Advertise message.  The client then chooses one of the
363   servers and sends a Request message to the server asking for
364   confirmed assignment of addresses and other configuration
365   information.  The server responds with a Reply message that contains
366   the confirmed addresses and configuration.
367
368   As described in the previous section, the client sends a Renew
369   message to the server to extend the lifetimes associated with its
370   addresses, allowing the client to continue to use those addresses
371   without interruption.
372
3732. Requirements
374
375   The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
376   SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
377   document, are to be interpreted as described in [1].
378
379   This document also makes use of internal conceptual variables to
380   describe protocol behavior and external variables that an
381   implementation must allow system administrators to change.  The
382   specific variable names, how their values change, and how their
383   settings influence protocol behavior are provided to demonstrate
384   protocol behavior.  An implementation is not required to have them in
385   the exact form described here, so long as its external behavior is
386   consistent with that described in this document.
387
388
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398
3993. Background
400
401   The IPv6 Specification provides the base architecture and design of
402   IPv6.  Related work in IPv6 that would best serve an implementor to
403   study includes the IPv6 Specification [3], the IPv6 Addressing
404   Architecture [5], IPv6 Stateless Address Autoconfiguration [17], IPv6
405   Neighbor Discovery Processing [13], and Dynamic Updates to DNS [22].
406   These specifications enable DHCP to build upon the IPv6 work to
407   provide both robust stateful autoconfiguration and autoregistration
408   of DNS Host Names.
409
410   The IPv6 Addressing Architecture specification [5] defines the
411   address scope that can be used in an IPv6 implementation, and the
412   various configuration architecture guidelines for network designers
413   of the IPv6 address space.  Two advantages of IPv6 are that support
414   for multicast is required and nodes can create link-local addresses
415   during initialization.  The availability of these features means that
416   a client can use its link-local address and a well-known multicast
417   address to discover and communicate with DHCP servers or relay agents
418   on its link.
419
420   IPv6 Stateless Address Autoconfiguration [17] specifies procedures by
421   which a node may autoconfigure addresses based on router
422   advertisements [13], and the use of a valid lifetime to support
423   renumbering of addresses on the Internet.  In addition, the protocol
424   interaction by which a node begins stateless or stateful
425   autoconfiguration is specified.  DHCP is one vehicle to perform
426   stateful autoconfiguration.  Compatibility with stateless address
427   autoconfiguration is a design requirement of DHCP.
428
429   IPv6 Neighbor Discovery [13] is the node discovery protocol in IPv6
430   which replaces and enhances functions of ARP [14].  To understand
431   IPv6 and stateless address autoconfiguration, it is strongly
432   recommended that implementors understand IPv6 Neighbor Discovery.
433
434   Dynamic Updates to DNS [22] is a specification that supports the
435   dynamic update of DNS records for both IPv4 and IPv6.  DHCP can use
436   the dynamic updates to DNS to integrate addresses and name space to
437   not only support autoconfiguration, but also autoregistration in
438   IPv6.
439
4404. Terminology
441
442   This sections defines terminology specific to IPv6 and DHCP used in
443   this document.
444
445
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454
4554.1. IPv6 Terminology
456
457   IPv6 terminology relevant to this specification from the IPv6
458   Protocol [3], IPv6 Addressing Architecture [5], and IPv6 Stateless
459   Address Autoconfiguration [17] is included below.
460
461      address                   An IP layer identifier for an interface
462                                or a set of interfaces.
463
464      host                      Any node that is not a router.
465
466      IP                        Internet Protocol Version 6 (IPv6).  The
467                                terms IPv4 and IPv6 are used only in
468                                contexts where it is necessary to avoid
469                                ambiguity.
470
471      interface                 A node's attachment to a link.
472
473      link                      A communication facility or medium over
474                                which nodes can communicate at the link
475                                layer, i.e., the layer immediately
476                                below IP.  Examples are Ethernet (simple
477                                or bridged); Token Ring; PPP links,
478                                X.25, Frame Relay, or ATM networks; and
479                                Internet (or higher) layer "tunnels",
480                                such as tunnels over IPv4 or IPv6
481                                itself.
482
483      link-layer identifier     A link-layer identifier for an
484                                interface.  Examples include IEEE 802
485                                addresses for Ethernet or Token Ring
486                                network interfaces, and E.164 addresses
487                                for ISDN links.
488
489      link-local address        An IPv6 address having a link-only
490                                scope, indicated by having the prefix
491                                (FE80::/10), that can be used to reach
492                                neighboring nodes attached to the same
493                                link.  Every interface has a link-local
494                                address.
495
496      multicast address         An identifier for a set of interfaces
497                                (typically belonging to different
498                                nodes).  A packet sent to a multicast
499                                address is delivered to all interfaces
500                                identified by that address.
501
502      neighbor                  A node attached to the same link.
503
504
505
506Droms, et al.               Standards Track                     [Page 9]
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508RFC 3315                     DHCP for IPv6                     July 2003
509
510
511      node                      A device that implements IP.
512
513      packet                    An IP header plus payload.
514
515      prefix                    The initial bits of an address, or a
516                                set of IP addresses that share the same
517                                initial bits.
518
519      prefix length             The number of bits in a prefix.
520
521      router                    A node that forwards IP packets not
522                                explicitly addressed to itself.
523
524      unicast address           An identifier for a single interface.
525                                A packet sent to a unicast address is
526                                delivered to the interface identified by
527                                that address.
528
5294.2. DHCP Terminology
530
531   Terminology specific to DHCP can be found below.
532
533      appropriate to the link   An address is "appropriate to the link"
534                                when the address is consistent with the
535                                DHCP server's knowledge of the network
536                                topology, prefix assignment and address
537                                assignment policies.
538
539      binding                   A binding (or, client binding) is a
540                                group of server data records containing
541                                the information the server has about
542                                the addresses in an IA or configuration
543                                information explicitly assigned to the
544                                client.  Configuration information that
545                                has been returned to a client through a
546                                policy - for example, the information
547                                returned to all clients on the same
548                                link - does not require a binding.  A
549                                binding containing information about
550                                an IA is indexed by the tuple <DUID,
551                                IA-type, IAID> (where IA-type is the
552                                type of address in the IA; for example,
553                                temporary).  A binding containing
554                                configuration information for a client
555                                is indexed by <DUID>.
556
557
558
559
560
561
562Droms, et al.               Standards Track                    [Page 10]
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564RFC 3315                     DHCP for IPv6                     July 2003
565
566
567      configuration parameter   An element of the configuration
568                                information set on the server and
569                                delivered to the client using DHCP.
570                                Such parameters may be used to carry
571                                information to be used by a node to
572                                configure its network subsystem and
573                                enable communication on a link or
574                                internetwork, for example.
575
576      DHCP                      Dynamic Host Configuration Protocol
577                                for IPv6.  The terms DHCPv4 and DHCPv6
578                                are used only in contexts where it is
579                                necessary to avoid ambiguity.
580
581      DHCP client (or client)   A node that initiates requests on a link
582                                to obtain configuration parameters from
583                                one or more DHCP servers.
584
585      DHCP domain               A set of links managed by DHCP and
586                                operated by a single administrative
587                                entity.
588
589      DHCP realm                A name used to identify the DHCP
590                                administrative domain from which a DHCP
591                                authentication key was selected.
592
593      DHCP relay agent (or relay agent) A node that acts as an
594                                intermediary to deliver DHCP messages
595                                between clients and servers, and is on
596                                the same link as the client.
597
598      DHCP server (or server)   A node that responds to requests from
599                                clients, and may or may not be on the
600                                same link as the client(s).
601
602      DUID                      A DHCP Unique IDentifier for a DHCP
603                                participant; each DHCP client and server
604                                has exactly one DUID.  See section 9 for
605                                details of the ways in which a DUID may
606                                be constructed.
607
608      Identity association (IA) A collection of addresses assigned to
609                                a client.  Each IA has an associated
610                                IAID.  A client may have more than one
611                                IA assigned to it; for example, one for
612                                each of its interfaces.
613
614
615
616
617
618Droms, et al.               Standards Track                    [Page 11]
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620RFC 3315                     DHCP for IPv6                     July 2003
621
622
623                                Each IA holds one type of address;
624                                for example, an identity association
625                                for temporary addresses (IA_TA) holds
626                                temporary addresses (see "identity
627                                association for temporary addresses").
628                                Throughout this document, "IA" is used
629                                to refer to an identity association
630                                without identifying the type of
631                                addresses in the IA.
632
633      Identity association identifier (IAID) An identifier for an IA,
634                                chosen by the client.  Each IA has an
635                                IAID, which is chosen to be unique among
636                                all IAIDs for IAs belonging to that
637                                client.
638
639      Identity association for non-temporary addresses (IA_NA) An IA
640                                that carries assigned addresses that are
641                                not temporary addresses (see "identity
642                                association for temporary addresses")
643
644      Identity association for temporary addresses (IA_TA) An IA that
645                                carries temporary addresses (see RFC
646                                3041 [12]).
647
648      message                   A unit of data carried as the payload
649                                of a UDP datagram, exchanged among DHCP
650                                servers, relay agents and clients.
651
652      Reconfigure key           A key supplied to a client by a server
653                                used to provide security for Reconfigure
654                                messages.
655
656      relaying                  A DHCP relay agent relays DHCP messages
657                                between DHCP participants.
658
659      transaction ID            An opaque value used to match responses
660                                with replies initiated either by a
661                                client or server.
662
6635. DHCP Constants
664
665   This section describes various program and networking constants used
666   by DHCP.
667
668
669
670
671
672
673
674Droms, et al.               Standards Track                    [Page 12]
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676RFC 3315                     DHCP for IPv6                     July 2003
677
678
6795.1. Multicast Addresses
680
681   DHCP makes use of the following multicast addresses:
682
683      All_DHCP_Relay_Agents_and_Servers (FF02::1:2) A link-scoped
684                  multicast address used by a client to communicate with
685                  neighboring (i.e., on-link) relay agents and servers.
686                  All servers and relay agents are members of this
687                  multicast group.
688
689      All_DHCP_Servers (FF05::1:3) A site-scoped multicast address used
690                  by a relay agent to communicate with servers, either
691                  because the relay agent wants to send messages to
692                  all servers or because it does not know the unicast
693                  addresses of the servers.  Note that in order for
694                  a relay agent to use this address, it must have an
695                  address of sufficient scope to be reachable by the
696                  servers.  All servers within the site are members of
697                  this multicast group.
698
6995.2. UDP Ports
700
701   Clients listen for DHCP messages on UDP port 546.  Servers and relay
702   agents listen for DHCP messages on UDP port 547.
703
7045.3. DHCP Message Types
705
706   DHCP defines the following message types.  More detail on these
707   message types can be found in sections 6 and 7.  Message types not
708   listed here are reserved for future use.  The numeric encoding for
709   each message type is shown in parentheses.
710
711      SOLICIT (1)        A client sends a Solicit message to locate
712                         servers.
713
714      ADVERTISE (2)      A server sends an Advertise message to indicate
715                         that it is available for DHCP service, in
716                         response to a Solicit message received from a
717                         client.
718
719      REQUEST (3)        A client sends a Request message to request
720                         configuration parameters, including IP
721                         addresses, from a specific server.
722
723      CONFIRM (4)        A client sends a Confirm message to any
724                         available server to determine whether the
725                         addresses it was assigned are still appropriate
726                         to the link to which the client is connected.
727
728
729
730Droms, et al.               Standards Track                    [Page 13]
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732RFC 3315                     DHCP for IPv6                     July 2003
733
734
735      RENEW (5)          A client sends a Renew message to the server
736                         that originally provided the client's addresses
737                         and configuration parameters to extend the
738                         lifetimes on the addresses assigned to the
739                         client and to update other configuration
740                         parameters.
741
742      REBIND (6)         A client sends a Rebind message to any
743                         available server to extend the lifetimes on the
744                         addresses assigned to the client and to update
745                         other configuration parameters; this message is
746                         sent after a client receives no response to a
747                         Renew message.
748
749      REPLY (7)          A server sends a Reply message containing
750                         assigned addresses and configuration parameters
751                         in response to a Solicit, Request, Renew,
752                         Rebind message received from a client.  A
753                         server sends a Reply message containing
754                         configuration parameters in response to an
755                         Information-request message.  A server sends a
756                         Reply message in response to a Confirm message
757                         confirming or denying that the addresses
758                         assigned to the client are appropriate to the
759                         link to which the client is connected.  A
760                         server sends a Reply message to acknowledge
761                         receipt of a Release or Decline message.
762
763      RELEASE (8)        A client sends a Release message to the server
764                         that assigned addresses to the client to
765                         indicate that the client will no longer use one
766                         or more of the assigned addresses.
767
768      DECLINE (9)        A client sends a Decline message to a server to
769                         indicate that the client has determined that
770                         one or more addresses assigned by the server
771                         are already in use on the link to which the
772                         client is connected.
773
774      RECONFIGURE (10)   A server sends a Reconfigure message to a
775                         client to inform the client that the server has
776                         new or updated configuration parameters, and
777                         that the client is to initiate a Renew/Reply
778                         or Information-request/Reply transaction with
779                         the server in order to receive the updated
780                         information.
781
782
783
784
785
786Droms, et al.               Standards Track                    [Page 14]
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788RFC 3315                     DHCP for IPv6                     July 2003
789
790
791      INFORMATION-REQUEST (11) A client sends an Information-request
792                         message to a server to request configuration
793                         parameters without the assignment of any IP
794                         addresses to the client.
795
796      RELAY-FORW (12)    A relay agent sends a Relay-forward message
797                         to relay messages to servers, either directly
798                         or through another relay agent.  The received
799                         message, either a client message or a
800                         Relay-forward message from another relay
801                         agent, is encapsulated in an option in the
802                         Relay-forward message.
803
804      RELAY-REPL (13)    A server sends a Relay-reply message to a relay
805                         agent containing a message that the relay
806                         agent delivers to a client.  The Relay-reply
807                         message may be relayed by other relay agents
808                         for delivery to the destination relay agent.
809
810                         The server encapsulates the client message as
811                         an option in the Relay-reply message, which the
812                         relay agent extracts and relays to the client.
813
8145.4. Status Codes
815
816   DHCPv6 uses status codes to communicate the success or failure of
817   operations requested in messages from clients and servers, and to
818   provide additional information about the specific cause of the
819   failure of a message.  The specific status codes are defined in
820   section 24.4.
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842Droms, et al.               Standards Track                    [Page 15]
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844RFC 3315                     DHCP for IPv6                     July 2003
845
846
8475.5. Transmission and Retransmission Parameters
848
849   This section presents a table of values used to describe the message
850   transmission behavior of clients and servers.
851
852   Parameter     Default  Description
853   -------------------------------------
854   SOL_MAX_DELAY     1 sec   Max delay of first Solicit
855   SOL_TIMEOUT       1 sec   Initial Solicit timeout
856   SOL_MAX_RT      120 secs  Max Solicit timeout value
857   REQ_TIMEOUT       1 sec   Initial Request timeout
858   REQ_MAX_RT       30 secs  Max Request timeout value
859   REQ_MAX_RC       10       Max Request retry attempts
860   CNF_MAX_DELAY     1 sec   Max delay of first Confirm
861   CNF_TIMEOUT       1 sec   Initial Confirm timeout
862   CNF_MAX_RT        4 secs  Max Confirm timeout
863   CNF_MAX_RD       10 secs  Max Confirm duration
864   REN_TIMEOUT      10 secs  Initial Renew timeout
865   REN_MAX_RT      600 secs  Max Renew timeout value
866   REB_TIMEOUT      10 secs  Initial Rebind timeout
867   REB_MAX_RT      600 secs  Max Rebind timeout value
868   INF_MAX_DELAY     1 sec   Max delay of first Information-request
869   INF_TIMEOUT       1 sec   Initial Information-request timeout
870   INF_MAX_RT      120 secs  Max Information-request timeout value
871   REL_TIMEOUT       1 sec   Initial Release timeout
872   REL_MAX_RC        5       MAX Release attempts
873   DEC_TIMEOUT       1 sec   Initial Decline timeout
874   DEC_MAX_RC        5       Max Decline attempts
875   REC_TIMEOUT       2 secs  Initial Reconfigure timeout
876   REC_MAX_RC        8       Max Reconfigure attempts
877   HOP_COUNT_LIMIT  32       Max hop count in a Relay-forward message
878
8795.6  Representation of time values and "Infinity" as a time value
880
881   All time values for lifetimes, T1 and T2 are unsigned integers.  The
882   value 0xffffffff is taken to mean "infinity" when used as a lifetime
883   (as in RFC2461 [17]) or a value for T1 or T2.
884
8856. Client/Server Message Formats
886
887   All DHCP messages sent between clients and servers share an identical
888   fixed format header and a variable format area for options.
889
890   All values in the message header and in options are in network byte
891   order.
892
893
894
895
896
897
898Droms, et al.               Standards Track                    [Page 16]
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900RFC 3315                     DHCP for IPv6                     July 2003
901
902
903   Options are stored serially in the options field, with no padding
904   between the options.  Options are byte-aligned but are not aligned in
905   any other way such as on 2 or 4 byte boundaries.
906
907   The following diagram illustrates the format of DHCP messages sent
908   between clients and servers:
909
910       0                   1                   2                   3
911       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
912      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
913      |    msg-type   |               transaction-id                  |
914      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
915      |                                                               |
916      .                            options                            .
917      .                           (variable)                          .
918      |                                                               |
919      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
920
921      msg-type             Identifies the DHCP message type; the
922                           available message types are listed in
923                           section 5.3.
924
925      transaction-id       The transaction ID for this message exchange.
926
927      options              Options carried in this message; options are
928                           described in section 22.
929
9307. Relay Agent/Server Message Formats
931
932   Relay agents exchange messages with servers to relay messages between
933   clients and servers that are not connected to the same link.
934
935   All values in the message header and in options are in network byte
936   order.
937
938   Options are stored serially in the options field, with no padding
939   between the options.  Options are byte-aligned but are not aligned in
940   any other way such as on 2 or 4 byte boundaries.
941
942
943
944
945
946
947
948
949
950
951
952
953
954Droms, et al.               Standards Track                    [Page 17]
955
956RFC 3315                     DHCP for IPv6                     July 2003
957
958
959   There are two relay agent messages, which share the following format:
960
961       0                   1                   2                   3
962       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
963      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
964      |    msg-type   |   hop-count   |                               |
965      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
966      |                                                               |
967      |                         link-address                          |
968      |                                                               |
969      |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
970      |                               |                               |
971      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
972      |                                                               |
973      |                         peer-address                          |
974      |                                                               |
975      |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
976      |                               |                               |
977      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
978      .                                                               .
979      .            options (variable number and length)   ....        .
980      |                                                               |
981      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
982
983   The following sections describe the use of the Relay Agent message
984   header.
985
9867.1. Relay-forward Message
987
988   The following table defines the use of message fields in a Relay-
989   forward message.
990
991      msg-type       RELAY-FORW
992
993      hop-count      Number of relay agents that have relayed this
994                     message.
995
996      link-address   A global or site-local address that will be used by
997                     the server to identify the link on which the client
998                     is located.
999
1000      peer-address   The address of the client or relay agent from which
1001                     the message to be relayed was received.
1002
1003      options        MUST include a "Relay Message option" (see
1004                     section 22.10); MAY include other options added by
1005                     the relay agent.
1006
1007
1008
1009
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1012RFC 3315                     DHCP for IPv6                     July 2003
1013
1014
10157.2. Relay-reply Message
1016
1017   The following table defines the use of message fields in a
1018   Relay-reply message.
1019
1020      msg-type       RELAY-REPL
1021
1022      hop-count      Copied from the Relay-forward message
1023
1024      link-address   Copied from the Relay-forward message
1025
1026      peer-address   Copied from the Relay-forward message
1027
1028      options        MUST include a "Relay Message option"; see
1029                     section 22.10; MAY include other options
1030
10318. Representation and Use of Domain Names
1032
1033   So that domain names may be encoded uniformly, a domain name or a
1034   list of domain names is encoded using the technique described in
1035   section 3.1 of RFC 1035 [10].  A domain name, or list of domain
1036   names, in DHCP MUST NOT be stored in compressed form, as described in
1037   section 4.1.4 of RFC 1035.
1038
10399. DHCP Unique Identifier (DUID)
1040
1041   Each DHCP client and server has a DUID.  DHCP servers use DUIDs to
1042   identify clients for the selection of configuration parameters and in
1043   the association of IAs with clients.  DHCP clients use DUIDs to
1044   identify a server in messages where a server needs to be identified.
1045   See sections 22.2 and 22.3 for the representation of a DUID in a DHCP
1046   message.
1047
1048   Clients and servers MUST treat DUIDs as opaque values and MUST only
1049   compare DUIDs for equality.  Clients and servers MUST NOT in any
1050   other way interpret DUIDs.  Clients and servers MUST NOT restrict
1051   DUIDs to the types defined in this document, as additional DUID types
1052   may be defined in the future.
1053
1054   The DUID is carried in an option because it may be variable length
1055   and because it is not required in all DHCP messages.  The DUID is
1056   designed to be unique across all DHCP clients and servers, and stable
1057   for any specific client or server - that is, the DUID used by a
1058   client or server SHOULD NOT change over time if at all possible; for
1059   example, a device's DUID should not change as a result of a change in
1060   the device's network hardware.
1061
1062
1063
1064
1065
1066Droms, et al.               Standards Track                    [Page 19]
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1068RFC 3315                     DHCP for IPv6                     July 2003
1069
1070
1071   The motivation for having more than one type of DUID is that the DUID
1072   must be globally unique, and must also be easy to generate.  The sort
1073   of globally-unique identifier that is easy to generate for any given
1074   device can differ quite widely.  Also, some devices may not contain
1075   any persistent storage.  Retaining a generated DUID in such a device
1076   is not possible, so the DUID scheme must accommodate such devices.
1077
10789.1. DUID Contents
1079
1080   A DUID consists of a two-octet type code represented in network byte
1081   order, followed by a variable number of octets that make up the
1082   actual identifier.  A DUID can be no more than 128 octets long (not
1083   including the type code).  The following types are currently defined:
1084
1085      1        Link-layer address plus time
1086      2        Vendor-assigned unique ID based on Enterprise Number
1087      3        Link-layer address
1088
1089   Formats for the variable field of the DUID for each of the above
1090   types are shown below.
1091
10929.2. DUID Based on Link-layer Address Plus Time [DUID-LLT]
1093
1094   This type of DUID consists of a two octet type field containing the
1095   value 1, a two octet hardware type code, four octets containing a
1096   time value, followed by link-layer address of any one network
1097   interface that is connected to the DHCP device at the time that the
1098   DUID is generated.  The time value is the time that the DUID is
1099   generated represented in seconds since midnight (UTC), January 1,
1100   2000, modulo 2^32.  The hardware type MUST be a valid hardware type
1101   assigned by the IANA as described in RFC 826 [14].  Both the time and
1102   the hardware type are stored in network byte order.  The link-layer
1103   address is stored in canonical form, as described in RFC 2464 [2].
1104
1105   The following diagram illustrates the format of a DUID-LLT:
1106
1107     0                   1                   2                   3
1108     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
1109    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1110    |               1               |    hardware type (16 bits)    |
1111    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1112    |                        time (32 bits)                         |
1113    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1114    .                                                               .
1115    .             link-layer address (variable length)              .
1116    .                                                               .
1117    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1118
1119
1120
1121
1122Droms, et al.               Standards Track                    [Page 20]
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1124RFC 3315                     DHCP for IPv6                     July 2003
1125
1126
1127   The choice of network interface can be completely arbitrary, as long
1128   as that interface provides a globally unique link-layer address for
1129   the link type, and the same DUID-LLT SHOULD be used in configuring
1130   all network interfaces connected to the device, regardless of which
1131   interface's link-layer address was used to generate the DUID-LLT.
1132
1133   Clients and servers using this type of DUID MUST store the DUID-LLT
1134   in stable storage, and MUST continue to use this DUID-LLT even if the
1135   network interface used to generate the DUID-LLT is removed.  Clients
1136   and servers that do not have any stable storage MUST NOT use this
1137   type of DUID.
1138
1139   Clients and servers that use this DUID SHOULD attempt to configure
1140   the time prior to generating the DUID, if that is possible, and MUST
1141   use some sort of time source (for example, a real-time clock) in
1142   generating the DUID, even if that time source could not be configured
1143   prior to generating the DUID.  The use of a time source makes it
1144   unlikely that two identical DUID-LLTs will be generated if the
1145   network interface is removed from the client and another client then
1146   uses the same network interface to generate a DUID-LLT.  A collision
1147   between two DUID-LLTs is very unlikely even if the clocks have not
1148   been configured prior to generating the DUID.
1149
1150   This method of DUID generation is recommended for all general purpose
1151   computing devices such as desktop computers and laptop computers, and
1152   also for devices such as printers, routers, and so on, that contain
1153   some form of writable non-volatile storage.
1154
1155   Despite our best efforts, it is possible that this algorithm for
1156   generating a DUID could result in a client identifier collision.  A
1157   DHCP client that generates a DUID-LLT using this mechanism MUST
1158   provide an administrative interface that replaces the existing DUID
1159   with a newly-generated DUID-LLT.
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
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1180RFC 3315                     DHCP for IPv6                     July 2003
1181
1182
11839.3. DUID Assigned by Vendor Based on Enterprise Number [DUID-EN]
1184
1185   This form of DUID is assigned by the vendor to the device.  It
1186   consists of the vendor's registered Private Enterprise Number as
1187   maintained by IANA [6] followed by a unique identifier assigned by
1188   the vendor.  The following diagram summarizes the structure of a
1189   DUID-EN:
1190
1191     0                   1                   2                   3
1192     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
1193    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1194    |               2               |       enterprise-number       |
1195    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1196    |   enterprise-number (contd)   |                               |
1197    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
1198    .                           identifier                          .
1199    .                       (variable length)                       .
1200    .                                                               .
1201    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1202
1203   The source of the identifier is left up to the vendor defining it,
1204   but each identifier part of each DUID-EN MUST be unique to the device
1205   that is using it, and MUST be assigned to the device at the time it
1206   is manufactured and stored in some form of non-volatile storage.  The
1207   generated DUID SHOULD be recorded in non-erasable storage.  The
1208   enterprise-number is the vendor's registered Private Enterprise
1209   Number as maintained by IANA [6].  The enterprise-number is stored as
1210   an unsigned 32 bit number.
1211
1212   An example DUID of this type might look like this:
1213
1214    +---+---+---+---+---+---+---+---+
1215    | 0 | 2 | 0 | 0 | 0 |  9| 12|192|
1216    +---+---+---+---+---+---+---+---+
1217    |132|221| 3 | 0 | 9 | 18|
1218    +---+---+---+---+---+---+
1219
1220   This example includes the two-octet type of 2, the Enterprise Number
1221   (9), followed by eight octets of identifier data
1222   (0x0CC084D303000912).
1223
12249.4. DUID Based on Link-layer Address [DUID-LL]
1225
1226   This type of DUID consists of two octets containing the DUID type 3,
1227   a two octet network hardware type code, followed by the link-layer
1228   address of any one network interface that is permanently connected to
1229   the client or server device.  For example, a host that has a network
1230   interface implemented in a chip that is unlikely to be removed and
1231
1232
1233
1234Droms, et al.               Standards Track                    [Page 22]
1235
1236RFC 3315                     DHCP for IPv6                     July 2003
1237
1238
1239   used elsewhere could use a DUID-LL.  The hardware type MUST be a
1240   valid hardware type assigned by the IANA, as described in RFC 826
1241   [14].  The hardware type is stored in network byte order.  The
1242   link-layer address is stored in canonical form, as described in RFC
1243   2464 [2].  The following diagram illustrates the format of a DUID-LL:
1244
1245     0                   1                   2                   3
1246     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
1247    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1248    |               3               |    hardware type (16 bits)    |
1249    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1250    .                                                               .
1251    .             link-layer address (variable length)              .
1252    .                                                               .
1253    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1254
1255   The choice of network interface can be completely arbitrary, as long
1256   as that interface provides a unique link-layer address and is
1257   permanently attached to the device on which the DUID-LL is being
1258   generated.  The same DUID-LL SHOULD be used in configuring all
1259   network interfaces connected to the device, regardless of which
1260   interface's link-layer address was used to generate the DUID.
1261
1262   DUID-LL is recommended for devices that have a permanently-connected
1263   network interface with a link-layer address, and do not have
1264   nonvolatile, writable stable storage.  DUID-LL MUST NOT be used by
1265   DHCP clients or servers that cannot tell whether or not a network
1266   interface is permanently attached to the device on which the DHCP
1267   client is running.
1268
126910. Identity Association
1270
1271   An "identity-association" (IA) is a construct through which a server
1272   and a client can identify, group, and manage a set of related IPv6
1273   addresses.  Each IA consists of an IAID and associated configuration
1274   information.
1275
1276   A client must associate at least one distinct IA with each of its
1277   network interfaces for which it is to request the assignment of IPv6
1278   addresses from a DHCP server.  The client uses the IAs assigned to an
1279   interface to obtain configuration information from a server for that
1280   interface.  Each IA must be associated with exactly one interface.
1281
1282   The IAID uniquely identifies the IA and must be chosen to be unique
1283   among the IAIDs on the client.  The IAID is chosen by the client.
1284   For any given use of an IA by the client, the IAID for that IA MUST
1285   be consistent across restarts of the DHCP client.  The client may
1286   maintain consistency either by storing the IAID in non-volatile
1287
1288
1289
1290Droms, et al.               Standards Track                    [Page 23]
1291
1292RFC 3315                     DHCP for IPv6                     July 2003
1293
1294
1295   storage or by using an algorithm that will consistently produce the
1296   same IAID as long as the configuration of the client has not changed.
1297   There may be no way for a client to maintain consistency of the IAIDs
1298   if it does not have non-volatile storage and the client's hardware
1299   configuration changes.
1300
1301   The configuration information in an IA consists of one or more IPv6
1302   addresses along with the times T1 and T2 for the IA.  See section
1303   22.4 for the representation of an IA in a DHCP message.
1304
1305   Each address in an IA has a preferred lifetime and a valid lifetime,
1306   as defined in RFC 2462 [17].  The lifetimes are transmitted from the
1307   DHCP server to the client in the IA option.  The lifetimes apply to
1308   the use of IPv6 addresses, as described in section 5.5.4 of RFC 2462.
1309
131011. Selecting Addresses for Assignment to an IA
1311
1312   A server selects addresses to be assigned to an IA according to the
1313   address assignment policies determined by the server administrator
1314   and the specific information the server determines about the client
1315   from some combination of the following sources:
1316
1317   -  The link to which the client is attached.  The server determines
1318      the link as follows:
1319
1320      *  If the server receives the message directly from the client and
1321         the source address in the IP datagram in which the message was
1322         received is a link-local address, then the client is on the
1323         same link to which the interface over which the message was
1324         received is attached.
1325
1326      *  If the server receives the message from a forwarding relay
1327         agent, then the client is on the same link as the one to which
1328         the interface, identified by the link-address field in the
1329         message from the relay agent, is attached.
1330
1331      *  If the server receives the message directly from the client and
1332         the source address in the IP datagram in which the message was
1333         received is not a link-local address, then the client is on the
1334         link identified by the source address in the IP datagram (note
1335         that this situation can occur only if the server has enabled
1336         the use of unicast message delivery by the client and the
1337         client has sent a message for which unicast delivery is
1338         allowed).
1339
1340   -  The DUID supplied by the client.
1341
1342   -  Other information in options supplied by the client.
1343
1344
1345
1346Droms, et al.               Standards Track                    [Page 24]
1347
1348RFC 3315                     DHCP for IPv6                     July 2003
1349
1350
1351   -  Other information in options supplied by the relay agent.
1352
1353   Any address assigned by a server that is based on an EUI-64
1354   identifier MUST include an interface identifier with the "u"
1355   (universal/local) and "g" (individual/group) bits of the interface
1356   identifier set appropriately, as indicated in section 2.5.1 of RFC
1357   2373 [5].
1358
1359   A server MUST NOT assign an address that is otherwise reserved for
1360   some other purpose.  For example, a server MUST NOT assign reserved
1361   anycast addresses, as defined in RFC 2526, from any subnet.
1362
136312. Management of Temporary Addresses
1364
1365   A client may request the assignment of temporary addresses (see RFC
1366   3041 [12] for the definition of temporary addresses).  DHCPv6
1367   handling of address assignment is no different for temporary
1368   addresses.  DHCPv6 says nothing about details of temporary addresses
1369   like lifetimes, how clients use temporary addresses, rules for
1370   generating successive temporary addresses, etc.
1371
1372   Clients ask for temporary addresses and servers assign them.
1373   Temporary addresses are carried in the Identity Association for
1374   Temporary Addresses (IA_TA) option (see section 22.5).  Each IA_TA
1375   option contains at most one temporary address for each of the
1376   prefixes on the link to which the client is attached.
1377
1378   The IAID number space for the IA_TA option IAID number space is
1379   separate from the IA_NA option IAID number space.
1380
1381   The server MAY update the DNS for a temporary address, as described
1382   in section 4 of RFC 3041.
1383
138413. Transmission of Messages by a Client
1385
1386   Unless otherwise specified in this document, or in a document that
1387   describes how IPv6 is carried over a specific type of link (for link
1388   types that do not support multicast), a client sends DHCP messages to
1389   the All_DHCP_Relay_Agents_and_Servers.
1390
1391   A client uses multicast to reach all servers or an individual server.
1392   An individual server is indicated by specifying that server's DUID in
1393   a Server Identifier option (see section 22.3) in the client's message
1394   (all servers will receive this message but only the indicated server
1395   will respond).  All servers are indicated by not supplying this
1396   option.
1397
1398
1399
1400
1401
1402Droms, et al.               Standards Track                    [Page 25]
1403
1404RFC 3315                     DHCP for IPv6                     July 2003
1405
1406
1407   A client may send some messages directly to a server using unicast,
1408   as described in section 22.12.
1409
141014. Reliability of Client Initiated Message Exchanges
1411
1412   DHCP clients are responsible for reliable delivery of messages in the
1413   client-initiated message exchanges described in sections 17 and 18.
1414   If a DHCP client fails to receive an expected response from a server,
1415   the client must retransmit its message.  This section describes the
1416   retransmission strategy to be used by clients in client-initiated
1417   message exchanges.
1418
1419   Note that the procedure described in this section is slightly
1420   modified when used with the Solicit message.  The modified procedure
1421   is described in section 17.1.2.
1422
1423   The client begins the message exchange by transmitting a message to
1424   the server.  The message exchange terminates when either the client
1425   successfully receives the appropriate response or responses from a
1426   server or servers, or when the message exchange is considered to have
1427   failed according to the retransmission mechanism described below.
1428
1429   The client retransmission behavior is controlled and described by the
1430   following variables:
1431
1432      RT     Retransmission timeout
1433
1434      IRT    Initial retransmission time
1435
1436      MRC    Maximum retransmission count
1437
1438      MRT    Maximum retransmission time
1439
1440      MRD    Maximum retransmission duration
1441
1442      RAND   Randomization factor
1443
1444   With each message transmission or retransmission, the client sets RT
1445   according to the rules given below.  If RT expires before the message
1446   exchange terminates, the client recomputes RT and retransmits the
1447   message.
1448
1449   Each of the computations of a new RT include a randomization factor
1450   (RAND), which is a random number chosen with a uniform distribution
1451   between -0.1 and +0.1.  The randomization factor is included to
1452   minimize synchronization of messages transmitted by DHCP clients.
1453
1454
1455
1456
1457
1458Droms, et al.               Standards Track                    [Page 26]
1459
1460RFC 3315                     DHCP for IPv6                     July 2003
1461
1462
1463   The algorithm for choosing a random number does not need to be
1464   cryptographically sound.  The algorithm SHOULD produce a different
1465   sequence of random numbers from each invocation of the DHCP client.
1466
1467   RT for the first message transmission is based on IRT:
1468
1469      RT = IRT + RAND*IRT
1470
1471   RT for each subsequent message transmission is based on the previous
1472   value of RT:
1473
1474      RT = 2*RTprev + RAND*RTprev
1475
1476   MRT specifies an upper bound on the value of RT (disregarding the
1477   randomization added by the use of RAND).  If MRT has a value of 0,
1478   there is no upper limit on the value of RT.  Otherwise:
1479
1480      if (RT > MRT)
1481         RT = MRT + RAND*MRT
1482
1483   MRC specifies an upper bound on the number of times a client may
1484   retransmit a message.  Unless MRC is zero, the message exchange fails
1485   once the client has transmitted the message MRC times.
1486
1487   MRD specifies an upper bound on the length of time a client may
1488   retransmit a message.  Unless MRD is zero, the message exchange fails
1489   once MRD seconds have elapsed since the client first transmitted the
1490   message.
1491
1492   If both MRC and MRD are non-zero, the message exchange fails whenever
1493   either of the conditions specified in the previous two paragraphs are
1494   met.
1495
1496   If both MRC and MRD are zero, the client continues to transmit the
1497   message until it receives a response.
1498
149915. Message Validation
1500
1501   Clients and servers SHOULD discard any messages that contain options
1502   that are not allowed to appear in the received message.  For example,
1503   an IA option is not allowed to appear in an Information-request
1504   message.  Clients and servers MAY choose to extract information from
1505   such a message if the information is of use to the recipient.
1506
1507   A server MUST discard any Solicit, Confirm, Rebind or
1508   Information-request messages it receives with a unicast destination
1509   address.
1510
1511
1512
1513
1514Droms, et al.               Standards Track                    [Page 27]
1515
1516RFC 3315                     DHCP for IPv6                     July 2003
1517
1518
1519   Message validation based on DHCP authentication is discussed in
1520   section 21.4.2.
1521
1522   If a server receives a message that contains options it should not
1523   contain (such as an Information-request message with an IA option),
1524   is missing options that it should contain, or is otherwise not valid,
1525   it MAY send a Reply (or Advertise as appropriate) with a Server
1526   Identifier option, a Client Identifier option if one was included in
1527   the message and a Status Code option with status UnSpecFail.
1528
152915.1. Use of Transaction IDs
1530
1531   The "transaction-id" field holds a value used by clients and servers
1532   to synchronize server responses to client messages.  A client SHOULD
1533   generate a random number that cannot easily be guessed or predicted
1534   to use as the transaction ID for each new message it sends.  Note
1535   that if a client generates easily predictable transaction
1536   identifiers, it may become more vulnerable to certain kinds of
1537   attacks from off-path intruders.  A client MUST leave the transaction
1538   ID unchanged in retransmissions of a message.
1539
154015.2. Solicit Message
1541
1542   Clients MUST discard any received Solicit messages.
1543
1544   Servers MUST discard any Solicit messages that do not include a
1545   Client Identifier option or that do include a Server Identifier
1546   option.
1547
154815.3. Advertise Message
1549
1550   Clients MUST discard any received Advertise messages that meet any of
1551   the following conditions:
1552
1553   -  the message does not include a Server Identifier option.
1554
1555   -  the message does not include a Client Identifier option.
1556
1557   -  the contents of the Client Identifier option does not match the
1558      client's DUID.
1559
1560   -  the "transaction-id" field value does not match the value the
1561      client used in its Solicit message.
1562
1563   Servers and relay agents MUST discard any received Advertise
1564   messages.
1565
1566
1567
1568
1569
1570Droms, et al.               Standards Track                    [Page 28]
1571
1572RFC 3315                     DHCP for IPv6                     July 2003
1573
1574
157515.4. Request Message
1576
1577   Clients MUST discard any received Request messages.
1578
1579   Servers MUST discard any received Request message that meet any of
1580   the following conditions:
1581
1582   -  the message does not include a Server Identifier option.
1583
1584   -  the contents of the Server Identifier option do not match the
1585      server's DUID.
1586
1587   -  the message does not include a Client Identifier option.
1588
158915.5. Confirm Message
1590
1591   Clients MUST discard any received Confirm messages.
1592
1593   Servers MUST discard any received Confirm messages that do not
1594   include a Client Identifier option or that do include a Server
1595   Identifier option.
1596
159715.6. Renew Message
1598
1599   Clients MUST discard any received Renew messages.
1600
1601   Servers MUST discard any received Renew message that meets any of the
1602   following conditions:
1603
1604   -  the message does not include a Server Identifier option.
1605
1606   -  the contents of the Server Identifier option does not match the
1607      server's identifier.
1608
1609   -  the message does not include a Client Identifier option.
1610
161115.7. Rebind Message
1612
1613   Clients MUST discard any received Rebind messages.
1614
1615   Servers MUST discard any received Rebind messages that do not include
1616   a Client Identifier option or that do include a Server Identifier
1617   option.
1618
1619
1620
1621
1622
1623
1624
1625
1626Droms, et al.               Standards Track                    [Page 29]
1627
1628RFC 3315                     DHCP for IPv6                     July 2003
1629
1630
163115.8. Decline Messages
1632
1633   Clients MUST discard any received Decline messages.
1634
1635   Servers MUST discard any received Decline message that meets any of
1636   the following conditions:
1637
1638   -  the message does not include a Server Identifier option.
1639
1640   -  the contents of the Server Identifier option does not match the
1641      server's identifier.
1642
1643   -  the message does not include a Client Identifier option.
1644
164515.9. Release Message
1646
1647   Clients MUST discard any received Release messages.
1648
1649   Servers MUST discard any received Release message that meets any of
1650   the following conditions:
1651
1652   -  the message does not include a Server Identifier option.
1653
1654   -  the contents of the Server Identifier option does not match the
1655      server's identifier.
1656
1657   -  the message does not include a Client Identifier option.
1658
165915.10. Reply Message
1660
1661   Clients MUST discard any received Reply message that meets any of the
1662   following conditions:
1663
1664   -  the message does not include a Server Identifier option.
1665
1666   -  the "transaction-id" field in the message does not match the value
1667      used in the original message.
1668
1669   If the client included a Client Identifier option in the original
1670   message, the Reply message MUST include a Client Identifier option
1671   and the contents of the Client Identifier option MUST match the DUID
1672   of the client; OR, if the client did not include a Client Identifier
1673   option in the original message, the Reply message MUST NOT include a
1674   Client Identifier option.
1675
1676   Servers and relay agents MUST discard any received Reply messages.
1677
1678
1679
1680
1681
1682Droms, et al.               Standards Track                    [Page 30]
1683
1684RFC 3315                     DHCP for IPv6                     July 2003
1685
1686
168715.11. Reconfigure Message
1688
1689   Servers and relay agents MUST discard any received Reconfigure
1690   messages.
1691
1692   Clients MUST discard any Reconfigure messages that meets any of the
1693   following conditions:
1694
1695   -  the message was not unicast to the client.
1696
1697   -  the message does not include a Server Identifier option.
1698
1699   -  the message does not include a Client Identifier option that
1700      contains the client's DUID.
1701
1702   -  the message does not contain a Reconfigure Message option and the
1703      msg-type must be a valid value.
1704
1705   -  the message includes any IA options and the msg-type in the
1706      Reconfigure Message option is INFORMATION-REQUEST.
1707
1708   -  the message does not include DHCP authentication:
1709
1710      *  the message does not contain an authentication option.
1711
1712      *  the message does not pass the authentication validation
1713         performed by the client.
1714
171515.12. Information-request Message
1716
1717   Clients MUST discard any received Information-request messages.
1718
1719   Servers MUST discard any received Information-request message that
1720   meets any of the following conditions:
1721
1722   -  The message includes a Server Identifier option and the DUID in
1723      the option does not match the server's DUID.
1724
1725   -  The message includes an IA option.
1726
172715.13. Relay-forward Message
1728
1729   Clients MUST discard any received Relay-forward messages.
1730
173115.14. Relay-reply Message
1732
1733   Clients and servers MUST discard any received Relay-reply messages.
1734
1735
1736
1737
1738Droms, et al.               Standards Track                    [Page 31]
1739
1740RFC 3315                     DHCP for IPv6                     July 2003
1741
1742
174316. Client Source Address and Interface Selection
1744
1745   When a client sends a DHCP message to the
1746   All_DHCP_Relay_Agents_and_Servers address, it SHOULD send the message
1747   through the interface for which configuration information is being
1748   requested.  However, the client MAY send the message through another
1749   interface attached to the same link, if and only if the client is
1750   certain the two interfaces are attached to the same link.  The client
1751   MUST use a link-local address assigned to the interface for which it
1752   is requesting configuration information as the source address in the
1753   header of the IP datagram.
1754
1755   When a client sends a DHCP message directly to a server using unicast
1756   (after receiving the Server Unicast option from that server), the
1757   source address in the header of the IP datagram MUST be an address
1758   assigned to the interface for which the client is interested in
1759   obtaining configuration and which is suitable for use by the server
1760   in responding to the client.
1761
176217. DHCP Server Solicitation
1763
1764   This section describes how a client locates servers that will assign
1765   addresses to IAs belonging to the client.
1766
1767   The client is responsible for creating IAs and requesting that a
1768   server assign IPv6 addresses to the IA.  The client first creates an
1769   IA and assigns it an IAID.  The client then transmits a Solicit
1770   message containing an IA option describing the IA.  Servers that can
1771   assign addresses to the IA respond to the client with an Advertise
1772   message.  The client then initiates a configuration exchange as
1773   described in section 18.
1774
1775   If the client will accept a Reply message with committed address
1776   assignments and other resources in response to the Solicit message,
1777   the client includes a Rapid Commit option (see section 22.14) in the
1778   Solicit message.
1779
178017.1. Client Behavior
1781
1782   A client uses the Solicit message to discover DHCP servers configured
1783   to assign addresses or return other configuration parameters on the
1784   link to which the client is attached.
1785
178617.1.1. Creation of Solicit Messages
1787
1788   The client sets the "msg-type" field to SOLICIT.  The client
1789   generates a transaction ID and inserts this value in the
1790   "transaction-id" field.
1791
1792
1793
1794Droms, et al.               Standards Track                    [Page 32]
1795
1796RFC 3315                     DHCP for IPv6                     July 2003
1797
1798
1799   The client MUST include a Client Identifier option to identify itself
1800   to the server.  The client includes IA options for any IAs to which
1801   it wants the server to assign addresses.  The client MAY include
1802   addresses in the IAs as a hint to the server about addresses for
1803   which the client has a preference.  The client MUST NOT include any
1804   other options in the Solicit message, except as specifically allowed
1805   in the definition of individual options.
1806
1807   The client uses IA_NA options to request the assignment of non-
1808   temporary addresses and uses IA_TA options to request the assignment
1809   of temporary addresses.  Either IA_NA or IA_TA options, or a
1810   combination of both, can be included in DHCP messages.
1811
1812   The client SHOULD include an Option Request option (see section 22.7)
1813   to indicate the options the client is interested in receiving.  The
1814   client MAY additionally include instances of those options that are
1815   identified in the Option Request option, with data values as hints to
1816   the server about parameter values the client would like to have
1817   returned.
1818
1819   The client includes a Reconfigure Accept option (see section 22.20)
1820   if the client is willing to accept Reconfigure messages from the
1821   server.
1822
182317.1.2. Transmission of Solicit Messages
1824
1825   The first Solicit message from the client on the interface MUST be
1826   delayed by a random amount of time between 0 and SOL_MAX_DELAY.  In
1827   the case of a Solicit message transmitted when DHCP is initiated by
1828   IPv6 Neighbor Discovery, the delay gives the amount of time to wait
1829   after IPv6 Neighbor Discovery causes the client to invoke the
1830   stateful address autoconfiguration protocol (see section 5.5.3 of RFC
1831   2462).  This random delay desynchronizes clients which start at the
1832   same time (for example, after a power outage).
1833
1834   The client transmits the message according to section 14, using the
1835   following parameters:
1836
1837      IRT   SOL_TIMEOUT
1838
1839      MRT   SOL_MAX_RT
1840
1841      MRC   0
1842
1843      MRD   0
1844
1845
1846
1847
1848
1849
1850Droms, et al.               Standards Track                    [Page 33]
1851
1852RFC 3315                     DHCP for IPv6                     July 2003
1853
1854
1855   If the client has included a Rapid Commit option in its Solicit
1856   message, the client terminates the waiting process as soon as a Reply
1857   message with a Rapid Commit option is received.
1858
1859   If the client is waiting for an Advertise message, the mechanism in
1860   section 14 is modified as follows for use in the transmission of
1861   Solicit messages.  The message exchange is not terminated by the
1862   receipt of an Advertise before the first RT has elapsed.  Rather, the
1863   client collects Advertise messages until the first RT has elapsed.
1864   Also, the first RT MUST be selected to be strictly greater than IRT
1865   by choosing RAND to be strictly greater than 0.
1866
1867   A client MUST collect Advertise messages for the first RT seconds,
1868   unless it receives an Advertise message with a preference value of
1869   255.  The preference value is carried in the Preference option
1870   (section 22.8).  Any Advertise that does not include a Preference
1871   option is considered to have a preference value of 0.  If the client
1872   receives an Advertise message that includes a Preference option with
1873   a preference value of 255, the client immediately begins a client-
1874   initiated message exchange (as described in section 18) by sending a
1875   Request message to the server from which the Advertise message was
1876   received.  If the client receives an Advertise message that does not
1877   include a Preference option with a preference value of 255, the
1878   client continues to wait until the first RT elapses.  If the first RT
1879   elapses and the client has received an Advertise message, the client
1880   SHOULD continue with a client-initiated message exchange by sending a
1881   Request message.
1882
1883   If the client does not receive any Advertise messages before the
1884   first RT has elapsed, it begins the retransmission mechanism
1885   described in section 14.  The client terminates the retransmission
1886   process as soon as it receives any Advertise message, and the client
1887   acts on the received Advertise message without waiting for any
1888   additional Advertise messages.
1889
1890   A DHCP client SHOULD choose MRC and MRD to be 0.  If the DHCP client
1891   is configured with either MRC or MRD set to a value other than 0, it
1892   MUST stop trying to configure the interface if the message exchange
1893   fails.  After the DHCP client stops trying to configure the
1894   interface, it SHOULD restart the reconfiguration process after some
1895   external event, such as user input, system restart, or when the
1896   client is attached to a new link.
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906Droms, et al.               Standards Track                    [Page 34]
1907
1908RFC 3315                     DHCP for IPv6                     July 2003
1909
1910
191117.1.3. Receipt of Advertise Messages
1912
1913   The client MUST ignore any Advertise message that includes a Status
1914   Code option containing the value NoAddrsAvail, with the exception
1915   that the client MAY display the associated status message to the
1916   user.
1917
1918   Upon receipt of one or more valid Advertise messages, the client
1919   selects one or more Advertise messages based upon the following
1920   criteria.
1921
1922   -  Those Advertise messages with the highest server preference value
1923      are preferred over all other Advertise messages.
1924
1925   -  Within a group of Advertise messages with the same server
1926      preference value, a client MAY select those servers whose
1927      Advertise messages advertise information of interest to the
1928      client.  For example, the client may choose a server that returned
1929      an advertisement with configuration options of interest to the
1930      client.
1931
1932   -  The client MAY choose a less-preferred server if that server has a
1933      better set of advertised parameters, such as the available
1934      addresses advertised in IAs.
1935
1936   Once a client has selected Advertise message(s), the client will
1937   typically store information about each server, such as server
1938   preference value, addresses advertised, when the advertisement was
1939   received, and so on.
1940
1941   If the client needs to select an alternate server in the case that a
1942   chosen server does not respond, the client chooses the next server
1943   according to the criteria given above.
1944
194517.1.4. Receipt of Reply Message
1946
1947   If the client includes a Rapid Commit option in the Solicit message,
1948   it will expect a Reply message that includes a Rapid Commit option in
1949   response.  The client discards any Reply messages it receives that do
1950   not include a Rapid Commit option.  If the client receives a valid
1951   Reply message that includes a Rapid Commit option, it processes the
1952   message as described in section 18.1.8.  If it does not receive such
1953   a Reply message and does receive a valid Advertise message, the
1954   client processes the Advertise message as described in section
1955   17.1.3.
1956
1957
1958
1959
1960
1961
1962Droms, et al.               Standards Track                    [Page 35]
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1964RFC 3315                     DHCP for IPv6                     July 2003
1965
1966
1967   If the client subsequently receives a valid Reply message that
1968   includes a Rapid Commit option, it either:
1969
1970      processes the Reply message as described in section 18.1.8, and
1971      discards any Reply messages received in response to the Request
1972      message, or
1973
1974      processes any Reply messages received in response to the Request
1975      message and discards the Reply message that includes the Rapid
1976      Commit option.
1977
197817.2. Server Behavior
1979
1980   A server sends an Advertise message in response to valid Solicit
1981   messages it receives to announce the availability of the server to
1982   the client.
1983
198417.2.1. Receipt of Solicit Messages
1985
1986   The server determines the information about the client and its
1987   location as described in section 11 and checks its administrative
1988   policy about responding to the client.  If the server is not
1989   permitted to respond to the client, the server discards the Solicit
1990   message.  For example, if the administrative policy for the server is
1991   that it may only respond to a client that is willing to accept a
1992   Reconfigure message, if the client indicates with a Reconfigure
1993   Accept option in the Solicit message that it will not accept a
1994   Reconfigure message, the servers discard the Solicit message.
1995
1996   If the client has included a Rapid Commit option in the Solicit
1997   message and the server has been configured to respond with committed
1998   address assignments and other resources, the server responds to the
1999   Solicit with a Reply message as described in section 17.2.3.
2000   Otherwise, the server ignores the Rapid Commit option and processes
2001   the remainder of the message as if no Rapid Commit option were
2002   present.
2003
200417.2.2. Creation and Transmission of Advertise Messages
2005
2006   The server sets the "msg-type" field to ADVERTISE and copies the
2007   contents of the transaction-id field from the Solicit message
2008   received from the client to the Advertise message.  The server
2009   includes its server identifier in a Server Identifier option and
2010   copies the Client Identifier from the Solicit message into the
2011   Advertise message.
2012
2013
2014
2015
2016
2017
2018Droms, et al.               Standards Track                    [Page 36]
2019
2020RFC 3315                     DHCP for IPv6                     July 2003
2021
2022
2023   The server MAY add a Preference option to carry the preference value
2024   for the Advertise message.  The server implementation SHOULD allow
2025   the setting of a server preference value by the administrator.  The
2026   server preference value MUST default to zero unless otherwise
2027   configured by the server administrator.
2028
2029   The server includes a Reconfigure Accept option if the server wants
2030   to require that the client accept Reconfigure messages.
2031
2032   The server includes options the server will return to the client in a
2033   subsequent Reply message.  The information in these options may be
2034   used by the client in the selection of a server if the client
2035   receives more than one Advertise message.  If the client has included
2036   an Option Request option in the Solicit message, the server includes
2037   options in the Advertise message containing configuration parameters
2038   for all of the options identified in the Option Request option that
2039   the server has been configured to return to the client.  The server
2040   MAY return additional options to the client if it has been configured
2041   to do so.  The server must be aware of the recommendations on packet
2042   sizes and the use of fragmentation in section 5 of RFC 2460.
2043
2044   If the Solicit message from the client included one or more IA
2045   options, the server MUST include IA options in the Advertise message
2046   containing any addresses that would be assigned to IAs contained in
2047   the Solicit message from the client.  If the client has included
2048   addresses in the IAs in the Solicit message, the server uses those
2049   addresses as hints about the addresses the client would like to
2050   receive.
2051
2052   If the server will not assign any addresses to any IAs in a
2053   subsequent Request from the client, the server MUST send an Advertise
2054   message to the client that includes only a Status Code option with
2055   code NoAddrsAvail and a status message for the user, a Server
2056   Identifier option with the server's DUID, and a Client Identifier
2057   option with the client's DUID.
2058
2059   If the Solicit message was received directly by the server, the
2060   server unicasts the Advertise message directly to the client using
2061   the address in the source address field from the IP datagram in which
2062   the Solicit message was received.  The Advertise message MUST be
2063   unicast on the link from which the Solicit message was received.
2064
2065   If the Solicit message was received in a Relay-forward message, the
2066   server constructs a Relay-reply message with the Advertise message in
2067   the payload of a "relay-message" option.  If the Relay-forward
2068   messages included an Interface-id option, the server copies that
2069   option to the Relay-reply message.  The server unicasts the
2070   Relay-reply message directly to the relay agent using the address in
2071
2072
2073
2074Droms, et al.               Standards Track                    [Page 37]
2075
2076RFC 3315                     DHCP for IPv6                     July 2003
2077
2078
2079   the source address field from the IP datagram in which the Relay-
2080   forward message was received.
2081
208217.2.3. Creation and Transmission of Reply Messages
2083
2084   The server MUST commit the assignment of any addresses or other
2085   configuration information message before sending a Reply message to a
2086   client in response to a Solicit message.
2087
2088   DISCUSSION:
2089
2090      When using the Solicit-Reply message exchange, the server commits
2091      the assignment of any addresses before sending the Reply message.
2092      The client can assume it has been assigned the addresses in the
2093      Reply message and does not need to send a Request message for
2094      those addresses.
2095
2096      Typically, servers that are configured to use the Solicit-Reply
2097      message exchange will be deployed so that only one server will
2098      respond to a Solicit message.  If more than one server responds,
2099      the client will only use the addresses from one of the servers,
2100      while the addresses from the other servers will be committed to
2101      the client but not used by the client.
2102
2103   The server includes a Rapid Commit option in the Reply message to
2104   indicate that the Reply is in response to a Solicit message.
2105
2106   The server includes a Reconfigure Accept option if the server wants
2107   to require that the client accept Reconfigure messages.
2108
2109   The server produces the Reply message as though it had received a
2110   Request message, as described in section 18.2.1.  The server
2111   transmits the Reply message as described in section 18.2.8.
2112
211318. DHCP Client-Initiated Configuration Exchange
2114
2115   A client initiates a message exchange with a server or servers to
2116   acquire or update configuration information of interest.  The client
2117   may initiate the configuration exchange as part of the operating
2118   system configuration process, when requested to do so by the
2119   application layer, when required by Stateless Address
2120   Autoconfiguration or as required to extend the lifetime of an address
2121   (Renew and Rebind messages).
2122
2123
2124
2125
2126
2127
2128
2129
2130Droms, et al.               Standards Track                    [Page 38]
2131
2132RFC 3315                     DHCP for IPv6                     July 2003
2133
2134
213518.1. Client Behavior
2136
2137   A client uses Request, Renew, Rebind, Release and Decline messages
2138   during the normal life cycle of addresses.  It uses Confirm to
2139   validate addresses when it may have moved to a new link.  It uses
2140   Information-Request messages when it needs configuration information
2141   but no addresses.
2142
2143   If the client has a source address of sufficient scope that can be
2144   used by the server as a return address, and the client has received a
2145   Server Unicast option (section 22.12) from the server, the client
2146   SHOULD unicast any Request, Renew, Release and Decline messages to
2147   the server.
2148
2149   DISCUSSION:
2150
2151      Use of unicast may avoid delays due to the relaying of messages by
2152      relay agents, as well as avoid overhead and duplicate responses by
2153      servers due to the delivery of client messages to multiple
2154      servers.  Requiring the client to relay all DHCP messages through
2155      a relay agent enables the inclusion of relay agent options in all
2156      messages sent by the client.  The server should enable the use of
2157      unicast only when relay agent options will not be used.
2158
215918.1.1. Creation and Transmission of Request Messages
2160
2161   The client uses a Request message to populate IAs with addresses and
2162   obtain other configuration information.  The client includes one or
2163   more IA options in the Request message.  The server then returns
2164   addresses and other information about the IAs to the client in IA
2165   options in a Reply message.
2166
2167   The client generates a transaction ID and inserts this value in the
2168   "transaction-id" field.
2169
2170   The client places the identifier of the destination server in a
2171   Server Identifier option.
2172
2173   The client MUST include a Client Identifier option to identify itself
2174   to the server.  The client adds any other appropriate options,
2175   including one or more IA options (if the client is requesting that
2176   the server assign it some network addresses).
2177
2178   The client MUST include an Option Request option (see section 22.7)
2179   to indicate the options the client is interested in receiving.  The
2180   client MAY include options with data values as hints to the server
2181   about parameter values the client would like to have returned.
2182
2183
2184
2185
2186Droms, et al.               Standards Track                    [Page 39]
2187
2188RFC 3315                     DHCP for IPv6                     July 2003
2189
2190
2191   The client includes a Reconfigure Accept option (see section 22.20)
2192   indicating whether or not the client is willing to accept Reconfigure
2193   messages from the server.
2194
2195   The client transmits the message according to section 14, using the
2196   following parameters:
2197
2198      IRT   REQ_TIMEOUT
2199
2200      MRT   REQ_MAX_RT
2201
2202      MRC   REQ_MAX_RC
2203
2204      MRD   0
2205
2206   If the message exchange fails, the client takes an action based on
2207   the client's local policy.  Examples of actions the client might take
2208   include:
2209
2210   -  Select another server from a list of servers known to the client;
2211      for example, servers that responded with an Advertise message.
2212
2213   -  Initiate the server discovery process described in section 17.
2214
2215   -  Terminate the configuration process and report failure.
2216
221718.1.2. Creation and Transmission of Confirm Messages
2218
2219   Whenever a client may have moved to a new link, the prefixes from the
2220   addresses assigned to the interfaces on that link may no longer be
2221   appropriate for the link to which the client is attached.  Examples
2222   of times when a client may have moved to a new link include:
2223
2224   o  The client reboots.
2225
2226   o  The client is physically connected to a wired connection.
2227
2228   o  The client returns from sleep mode.
2229
2230   o  The client using a wireless technology changes access points.
2231
2232   In any situation when a client may have moved to a new link, the
2233   client MUST initiate a Confirm/Reply message exchange.  The client
2234   includes any IAs assigned to the interface that may have moved to a
2235   new link, along with the addresses associated with those IAs, in its
2236
2237
2238
2239
2240
2241
2242Droms, et al.               Standards Track                    [Page 40]
2243
2244RFC 3315                     DHCP for IPv6                     July 2003
2245
2246
2247   Confirm message.  Any responding servers will indicate whether those
2248   addresses are appropriate for the link to which the client is
2249   attached with the status in the Reply message it returns to the
2250   client.
2251
2252   The client sets the "msg-type" field to CONFIRM.  The client
2253   generates a transaction ID and inserts this value in the
2254   "transaction-id" field.
2255
2256   The client MUST include a Client Identifier option to identify itself
2257   to the server.  The client includes IA options for all of the IAs
2258   assigned to the interface for which the Confirm message is being
2259   sent.  The IA options include all of the addresses the client
2260   currently has associated with those IAs.  The client SHOULD set the
2261   T1 and T2 fields in any IA_NA options, and the preferred-lifetime and
2262   valid-lifetime fields in the IA Address options to 0, as the server
2263   will ignore these fields.
2264
2265   The first Confirm message from the client on the interface MUST be
2266   delayed by a random amount of time between 0 and CNF_MAX_DELAY.  The
2267   client transmits the message according to section 14, using the
2268   following parameters:
2269
2270      IRT   CNF_TIMEOUT
2271
2272      MRT   CNF_MAX_RT
2273
2274      MRC   0
2275
2276      MRD   CNF_MAX_RD
2277
2278   If the client receives no responses before the message transmission
2279   process terminates, as described in section 14, the client SHOULD
2280   continue to use any IP addresses, using the last known lifetimes for
2281   those addresses, and SHOULD continue to use any other previously
2282   obtained configuration parameters.
2283
228418.1.3. Creation and Transmission of Renew Messages
2285
2286   To extend the valid and preferred lifetimes for the addresses
2287   associated with an IA, the client sends a Renew message to the server
2288   from which the client obtained the addresses in the IA containing an
2289   IA option for the IA.  The client includes IA Address options in the
2290   IA option for the addresses associated with the IA.  The server
2291   determines new lifetimes for the addresses in the IA according to the
2292   administrative configuration of the server.  The server may also add
2293
2294
2295
2296
2297
2298Droms, et al.               Standards Track                    [Page 41]
2299
2300RFC 3315                     DHCP for IPv6                     July 2003
2301
2302
2303   new addresses to the IA.  The server may remove addresses from the IA
2304   by setting the preferred and valid lifetimes of those addresses to
2305   zero.
2306
2307   The server controls the time at which the client contacts the server
2308   to extend the lifetimes on assigned addresses through the T1 and T2
2309   parameters assigned to an IA.
2310
2311   At time T1 for an IA, the client initiates a Renew/Reply message
2312   exchange to extend the lifetimes on any addresses in the IA.  The
2313   client includes an IA option with all addresses currently assigned to
2314   the IA in its Renew message.
2315
2316   If T1 or T2 is set to 0 by the server (for an IA_NA) or there are no
2317   T1 or T2 times (for an IA_TA), the client may send a Renew or Rebind
2318   message, respectively, at the client's discretion.
2319
2320   The client sets the "msg-type" field to RENEW.  The client generates
2321   a transaction ID and inserts this value in the "transaction-id"
2322   field.
2323
2324   The client places the identifier of the destination server in a
2325   Server Identifier option.
2326
2327   The client MUST include a Client Identifier option to identify itself
2328   to the server.  The client adds any appropriate options, including
2329   one or more IA options.  The client MUST include the list of
2330   addresses the client currently has associated with the IAs in the
2331   Renew message.
2332
2333   The client MUST include an Option Request option (see section 22.7)
2334   to indicate the options the client is interested in receiving.  The
2335   client MAY include options with data values as hints to the server
2336   about parameter values the client would like to have returned.
2337
2338   The client transmits the message according to section 14, using the
2339   following parameters:
2340
2341      IRT   REN_TIMEOUT
2342
2343      MRT   REN_MAX_RT
2344
2345      MRC   0
2346
2347      MRD   Remaining time until T2
2348
2349
2350
2351
2352
2353
2354Droms, et al.               Standards Track                    [Page 42]
2355
2356RFC 3315                     DHCP for IPv6                     July 2003
2357
2358
2359   The message exchange is terminated when time T2 is reached (see
2360   section 18.1.4), at which time the client begins a Rebind message
2361   exchange.
2362
236318.1.4. Creation and Transmission of Rebind Messages
2364
2365   At time T2 for an IA (which will only be reached if the server to
2366   which the Renew message was sent at time T1 has not responded), the
2367   client initiates a Rebind/Reply message exchange with any available
2368   server.  The client includes an IA option with all addresses
2369   currently assigned to the IA in its Rebind message.
2370
2371   The client sets the "msg-type" field to REBIND.  The client generates
2372   a transaction ID and inserts this value in the "transaction-id"
2373   field.
2374
2375   The client MUST include a Client Identifier option to identify itself
2376   to the server.  The client adds any appropriate options, including
2377   one or more IA options.  The client MUST include the list of
2378   addresses the client currently has associated with the IAs in the
2379   Rebind message.
2380
2381   The client MUST include an Option Request option (see section 22.7)
2382   to indicate the options the client is interested in receiving.  The
2383   client MAY include options with data values as hints to the server
2384   about parameter values the client would like to have returned.
2385
2386   The client transmits the message according to section 14, using the
2387   following parameters:
2388
2389      IRT   REB_TIMEOUT
2390
2391      MRT   REB_MAX_RT
2392
2393      MRC   0
2394
2395      MRD   Remaining time until valid lifetimes of all addresses have
2396            expired
2397
2398   The message exchange is terminated when the valid lifetimes of all
2399   the addresses assigned to the IA expire (see section 10), at which
2400   time the client has several alternative actions to choose from; for
2401   example:
2402
2403   -  The client may choose to use a Solicit message to locate a new
2404      DHCP server and send a Request for the expired IA to the new
2405      server.
2406
2407
2408
2409
2410Droms, et al.               Standards Track                    [Page 43]
2411
2412RFC 3315                     DHCP for IPv6                     July 2003
2413
2414
2415   -  The client may have other addresses in other IAs, so the client
2416      may choose to discard the expired IA and use the addresses in the
2417      other IAs.
2418
241918.1.5. Creation and Transmission of Information-request Messages
2420
2421   The client uses an Information-request message to obtain
2422   configuration information without having addresses assigned to it.
2423
2424   The client sets the "msg-type" field to INFORMATION-REQUEST.  The
2425   client generates a transaction ID and inserts this value in the
2426   "transaction-id" field.
2427
2428   The client SHOULD include a Client Identifier option to identify
2429   itself to the server.  If the client does not include a Client
2430   Identifier option, the server will not be able to return any client-
2431   specific options to the client, or the server may choose not to
2432   respond to the message at all.  The client MUST include a Client
2433   Identifier option if the Information-Request message will be
2434   authenticated.
2435
2436   The client MUST include an Option Request option (see section 22.7)
2437   to indicate the options the client is interested in receiving.  The
2438   client MAY include options with data values as hints to the server
2439   about parameter values the client would like to have returned.
2440
2441   The first Information-request message from the client on the
2442   interface MUST be delayed by a random amount of time between 0 and
2443   INF_MAX_DELAY.  The client transmits the message according to section
2444   14, using the following parameters:
2445
2446      IRT   INF_TIMEOUT
2447
2448      MRT   INF_MAX_RT
2449
2450      MRC   0
2451
2452      MRD   0
2453
245418.1.6. Creation and Transmission of Release Messages
2455
2456   To release one or more addresses, a client sends a Release message to
2457   the server.
2458
2459   The client sets the "msg-type" field to RELEASE.  The client
2460   generates a transaction ID and places this value in the
2461   "transaction-id" field.
2462
2463
2464
2465
2466Droms, et al.               Standards Track                    [Page 44]
2467
2468RFC 3315                     DHCP for IPv6                     July 2003
2469
2470
2471   The client places the identifier of the server that allocated the
2472   address(es) in a Server Identifier option.
2473
2474   The client MUST include a Client Identifier option to identify itself
2475   to the server.  The client includes options containing the IAs for
2476   the addresses it is releasing in the "options" field.  The addresses
2477   to be released MUST be included in the IAs.  Any addresses for the
2478   IAs the client wishes to continue to use MUST NOT be added to the
2479   IAs.
2480
2481   The client MUST NOT use any of the addresses it is releasing as the
2482   source address in the Release message or in any subsequently
2483   transmitted message.
2484
2485   Because Release messages may be lost, the client should retransmit
2486   the Release if no Reply is received.  However, there are scenarios
2487   where the client may not wish to wait for the normal retransmission
2488   timeout before giving up (e.g., on power down).  Implementations
2489   SHOULD retransmit one or more times, but MAY choose to terminate the
2490   retransmission procedure early.
2491
2492   The client transmits the message according to section 14, using the
2493   following parameters:
2494
2495      IRT   REL_TIMEOUT
2496
2497      MRT   0
2498
2499      MRC   REL_MAX_RC
2500
2501      MRD   0
2502
2503   The client MUST stop using all of the addresses being released as
2504   soon as the client begins the Release message exchange process.  If
2505   addresses are released but the Reply from a DHCP server is lost, the
2506   client will retransmit the Release message, and the server may
2507   respond with a Reply indicating a status of NoBinding.  Therefore,
2508   the client does not treat a Reply message with a status of NoBinding
2509   in a Release message exchange as if it indicates an error.
2510
2511   Note that if the client fails to release the addresses, each address
2512   assigned to the IA will be reclaimed by the server when the valid
2513   lifetime of that address expires.
2514
2515
2516
2517
2518
2519
2520
2521
2522Droms, et al.               Standards Track                    [Page 45]
2523
2524RFC 3315                     DHCP for IPv6                     July 2003
2525
2526
252718.1.7. Creation and Transmission of Decline Messages
2528
2529   If a client detects that one or more addresses assigned to it by a
2530   server are already in use by another node, the client sends a Decline
2531   message to the server to inform it that the address is suspect.
2532
2533   The client sets the "msg-type" field to DECLINE.  The client
2534   generates a transaction ID and places this value in the
2535   "transaction-id" field.
2536
2537   The client places the identifier of the server that allocated the
2538   address(es) in a Server Identifier option.
2539
2540   The client MUST include a Client Identifier option to identify itself
2541   to the server.  The client includes options containing the IAs for
2542   the addresses it is declining in the "options" field.  The addresses
2543   to be declined MUST be included in the IAs.  Any addresses for the
2544   IAs the client wishes to continue to use should not be in added to
2545   the IAs.
2546
2547   The client MUST NOT use any of the addresses it is declining as the
2548   source address in the Decline message or in any subsequently
2549   transmitted message.
2550
2551   The client transmits the message according to section 14, using the
2552   following parameters:
2553
2554      IRT   DEC_TIMEOUT
2555
2556      MRT   0
2557
2558      MRC   DEC_MAX_RC
2559
2560      MRD   0
2561
2562   If addresses are declined but the Reply from a DHCP server is lost,
2563   the client will retransmit the Decline message, and the server may
2564   respond with a Reply indicating a status of NoBinding.  Therefore,
2565   the client does not treat a Reply message with a status of NoBinding
2566   in a Decline message exchange as if it indicates an error.
2567
256818.1.8. Receipt of Reply Messages
2569
2570   Upon the receipt of a valid Reply message in response to a Solicit
2571   (with a Rapid Commit option), Request, Confirm, Renew, Rebind or
2572   Information-request message, the client extracts the configuration
2573
2574
2575
2576
2577
2578Droms, et al.               Standards Track                    [Page 46]
2579
2580RFC 3315                     DHCP for IPv6                     July 2003
2581
2582
2583   information contained in the Reply.  The client MAY choose to report
2584   any status code or message from the status code option in the Reply
2585   message.
2586
2587   The client SHOULD perform duplicate address detection [17] on each of
2588   the addresses in any IAs it receives in the Reply message before
2589   using that address for traffic.  If any of the addresses are found to
2590   be in use on the link, the client sends a Decline message to the
2591   server as described in section 18.1.7.
2592
2593   If the Reply was received in response to a Solicit (with a Rapid
2594   Commit option), Request, Renew or Rebind message, the client updates
2595   the information it has recorded about IAs from the IA options
2596   contained in the Reply message:
2597
2598   -  Record T1 and T2 times.
2599
2600   -  Add any new addresses in the IA option to the IA as recorded by
2601      the client.
2602
2603   -  Update lifetimes for any addresses in the IA option that the
2604      client already has recorded in the IA.
2605
2606   -  Discard any addresses from the IA, as recorded by the client, that
2607      have a valid lifetime of 0 in the IA Address option.
2608
2609   -  Leave unchanged any information about addresses the client has
2610      recorded in the IA but that were not included in the IA from the
2611      server.
2612
2613   Management of the specific configuration information is detailed in
2614   the definition of each option in section 22.
2615
2616   If the client receives a Reply message with a Status Code containing
2617   UnspecFail, the server is indicating that it was unable to process
2618   the message due to an unspecified failure condition.  If the client
2619   retransmits the original message to the same server to retry the
2620   desired operation, the client MUST limit the rate at which it
2621   retransmits the message and limit the duration of the time during
2622   which it retransmits the message.
2623
2624   When the client receives a Reply message with a Status Code option
2625   with the value UseMulticast, the client records the receipt of the
2626   message and sends subsequent messages to the server through the
2627   interface on which the message was received using multicast.  The
2628   client resends the original message using multicast.
2629
2630
2631
2632
2633
2634Droms, et al.               Standards Track                    [Page 47]
2635
2636RFC 3315                     DHCP for IPv6                     July 2003
2637
2638
2639   When the client receives a NotOnLink status from the server in
2640   response to a Confirm message, the client performs DHCP server
2641   solicitation, as described in section 17, and client-initiated
2642   configuration as described in section 18.  If the client receives any
2643   Reply messages that do not indicate a NotOnLink status, the client
2644   can use the addresses in the IA and ignore any messages that indicate
2645   a NotOnLink status.
2646
2647   When the client receives a NotOnLink status from the server in
2648   response to a Request, the client can either re-issue the Request
2649   without specifying any addresses or restart the DHCP server discovery
2650   process (see section 17).
2651
2652   The client examines the status code in each IA individually.  If the
2653   status code is NoAddrsAvail, the client has received no usable
2654   addresses in the IA and may choose to try obtaining addresses for the
2655   IA from another server.  The client uses addresses and other
2656   information from any IAs that do not contain a Status Code option
2657   with the NoAddrsAvail code.  If the client receives no addresses in
2658   any of the IAs, it may either try another server (perhaps restarting
2659   the DHCP server discovery process) or use the Information-request
2660   message to obtain other configuration information only.
2661
2662   When the client receives a Reply message in response to a Renew or
2663   Rebind message, the client examines each IA independently.  For each
2664   IA in the original Renew or Rebind message, the client:
2665
2666   -  sends a Request message if the IA contained a Status Code option
2667      with the NoBinding status (and does not send any additional
2668      Renew/Rebind messages)
2669
2670   -  sends a Renew/Rebind if the IA is not in the Reply message
2671
2672   -  otherwise accepts the information in the IA
2673
2674   When the client receives a valid Reply message in response to a
2675   Release message, the client considers the Release event completed,
2676   regardless of the Status Code option(s) returned by the server.
2677
2678   When the client receives a valid Reply message in response to a
2679   Decline message, the client considers the Decline event completed,
2680   regardless of the Status Code option(s) returned by the server.
2681
268218.2. Server Behavior
2683
2684   For this discussion, the Server is assumed to have been configured in
2685   an implementation specific manner with configuration of interest to
2686   clients.
2687
2688
2689
2690Droms, et al.               Standards Track                    [Page 48]
2691
2692RFC 3315                     DHCP for IPv6                     July 2003
2693
2694
2695   In most instances, the server will send a Reply in response to a
2696   client message.  This Reply message MUST always contain the Server
2697   Identifier option containing the server's DUID and the Client
2698   Identifier option from the client message if one was present.
2699
2700   In most Reply messages, the server includes options containing
2701   configuration information for the client.  The server must be aware
2702   of the recommendations on packet sizes and the use of fragmentation
2703   in section 5 of RFC 2460.  If the client included an Option Request
2704   option in its message, the server includes options in the Reply
2705   message containing configuration parameters for all of the options
2706   identified in the Option Request option that the server has been
2707   configured to return to the client.  The server MAY return additional
2708   options to the client if it has been configured to do so.
2709
271018.2.1. Receipt of Request Messages
2711
2712   When the server receives a Request message via unicast from a client
2713   to which the server has not sent a unicast option, the server
2714   discards the Request message and responds with a Reply message
2715   containing a Status Code option with the value UseMulticast, a Server
2716   Identifier option containing the server's DUID, the Client Identifier
2717   option from the client message, and no other options.
2718
2719   When the server receives a valid Request message, the server creates
2720   the bindings for that client according to the server's policy and
2721   configuration information and records the IAs and other information
2722   requested by the client.
2723
2724   The server constructs a Reply message by setting the "msg-type" field
2725   to REPLY, and copying the transaction ID from the Request message
2726   into the transaction-id field.
2727
2728   The server MUST include a Server Identifier option containing the
2729   server's DUID and the Client Identifier option from the Request
2730   message in the Reply message.
2731
2732   If the server finds that the prefix on one or more IP addresses in
2733   any IA in the message from the client is not appropriate for the link
2734   to which the client is connected, the server MUST return the IA to
2735   the client with a Status Code option with the value NotOnLink.
2736
2737   If the server cannot assign any addresses to an IA in the message
2738   from the client, the server MUST include the IA in the Reply message
2739   with no addresses in the IA and a Status Code option in the IA
2740   containing status code NoAddrsAvail.
2741
2742
2743
2744
2745
2746Droms, et al.               Standards Track                    [Page 49]
2747
2748RFC 3315                     DHCP for IPv6                     July 2003
2749
2750
2751   For any IAs to which the server can assign addresses, the server
2752   includes the IA with addresses and other configuration parameters,
2753   and records the IA as a new client binding.
2754
2755   The server includes a Reconfigure Accept option if the server wants
2756   to require that the client accept Reconfigure messages.
2757
2758   The server includes other options containing configuration
2759   information to be returned to the client as described in section
2760   18.2.
2761
2762   If the server finds that the client has included an IA in the Request
2763   message for which the server already has a binding that associates
2764   the IA with the client, the client has resent a Request message for
2765   which it did not receive a Reply message.  The server either resends
2766   a previously cached Reply message or sends a new Reply message.
2767
276818.2.2. Receipt of Confirm Messages
2769
2770   When the server receives a Confirm message, the server determines
2771   whether the addresses in the Confirm message are appropriate for the
2772   link to which the client is attached.  If all of the addresses in the
2773   Confirm message pass this test, the server returns a status of
2774   Success.  If any of the addresses do not pass this test, the server
2775   returns a status of NotOnLink.  If the server is unable to perform
2776   this test (for example, the server does not have information about
2777   prefixes on the link to which the client is connected), or there were
2778   no addresses in any of the IAs sent by the client, the server MUST
2779   NOT send a reply to the client.
2780
2781   The server ignores the T1 and T2 fields in the IA options and the
2782   preferred-lifetime and valid-lifetime fields in the IA Address
2783   options.
2784
2785   The server constructs a Reply message by setting the "msg-type" field
2786   to REPLY, and copying the transaction ID from the Confirm message
2787   into the transaction-id field.
2788
2789   The server MUST include a Server Identifier option containing the
2790   server's DUID and the Client Identifier option from the Confirm
2791   message in the Reply message.  The server includes a Status Code
2792   option indicating the status of the Confirm message.
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802Droms, et al.               Standards Track                    [Page 50]
2803
2804RFC 3315                     DHCP for IPv6                     July 2003
2805
2806
280718.2.3. Receipt of Renew Messages
2808
2809   When the server receives a Renew message via unicast from a client to
2810   which the server has not sent a unicast option, the server discards
2811   the Renew message and responds with a Reply message containing a
2812   Status Code option with the value UseMulticast, a Server Identifier
2813   option containing the server's DUID, the Client Identifier option
2814   from the client message, and no other options.
2815
2816   When the server receives a Renew message that contains an IA option
2817   from a client, it locates the client's binding and verifies that the
2818   information in the IA from the client matches the information stored
2819   for that client.
2820
2821   If the server cannot find a client entry for the IA the server
2822   returns the IA containing no addresses with a Status Code option set
2823   to NoBinding in the Reply message.
2824
2825   If the server finds that any of the addresses are not appropriate for
2826   the link to which the client is attached, the server returns the
2827   address to the client with lifetimes of 0.
2828
2829   If the server finds the addresses in the IA for the client then the
2830   server sends back the IA to the client with new lifetimes and T1/T2
2831   times.  The server may choose to change the list of addresses and the
2832   lifetimes of addresses in IAs that are returned to the client.
2833
2834   The server constructs a Reply message by setting the "msg-type" field
2835   to REPLY, and copying the transaction ID from the Renew message into
2836   the transaction-id field.
2837
2838   The server MUST include a Server Identifier option containing the
2839   server's DUID and the Client Identifier option from the Renew message
2840   in the Reply message.
2841
2842   The server includes other options containing configuration
2843   information to be returned to the client as described in section
2844   18.2.
2845
284618.2.4. Receipt of Rebind Messages
2847
2848   When the server receives a Rebind message that contains an IA option
2849   from a client, it locates the client's binding and verifies that the
2850   information in the IA from the client matches the information stored
2851   for that client.
2852
2853
2854
2855
2856
2857
2858Droms, et al.               Standards Track                    [Page 51]
2859
2860RFC 3315                     DHCP for IPv6                     July 2003
2861
2862
2863   If the server cannot find a client entry for the IA and the server
2864   determines that the addresses in the IA are not appropriate for the
2865   link to which the client's interface is attached according to the
2866   server's explicit configuration information, the server MAY send a
2867   Reply message to the client containing the client's IA, with the
2868   lifetimes for the addresses in the IA set to zero.  This Reply
2869   constitutes an explicit notification to the client that the addresses
2870   in the IA are no longer valid.  In this situation, if the server does
2871   not send a Reply message it silently discards the Rebind message.
2872
2873   If the server finds that any of the addresses are no longer
2874   appropriate for the link to which the client is attached, the server
2875   returns the address to the client with lifetimes of 0.
2876
2877   If the server finds the addresses in the IA for the client then the
2878   server SHOULD send back the IA to the client with new lifetimes and
2879   T1/T2 times.
2880
2881   The server constructs a Reply message by setting the "msg-type" field
2882   to REPLY, and copying the transaction ID from the Rebind message into
2883   the transaction-id field.
2884
2885   The server MUST include a Server Identifier option containing the
2886   server's DUID and the Client Identifier option from the Rebind
2887   message in the Reply message.
2888
2889   The server includes other options containing configuration
2890   information to be returned to the client as described in section
2891   18.2.
2892
289318.2.5. Receipt of Information-request Messages
2894
2895   When the server receives an Information-request message, the client
2896   is requesting configuration information that does not include the
2897   assignment of any addresses.  The server determines all configuration
2898   parameters appropriate to the client, based on the server
2899   configuration policies known to the server.
2900
2901   The server constructs a Reply message by setting the "msg-type" field
2902   to REPLY, and copying the transaction ID from the Information-request
2903   message into the transaction-id field.
2904
2905   The server MUST include a Server Identifier option containing the
2906   server's DUID in the Reply message.  If the client included a Client
2907   Identification option in the Information-request message, the server
2908   copies that option to the Reply message.
2909
2910
2911
2912
2913
2914Droms, et al.               Standards Track                    [Page 52]
2915
2916RFC 3315                     DHCP for IPv6                     July 2003
2917
2918
2919   The server includes options containing configuration information to
2920   be returned to the client as described in section 18.2.
2921
2922   If the Information-request message received from the client did not
2923   include a Client Identifier option, the server SHOULD respond with a
2924   Reply message containing any configuration parameters that are not
2925   determined by the client's identity.  If the server chooses not to
2926   respond, the client may continue to retransmit the
2927   Information-request message indefinitely.
2928
292918.2.6. Receipt of Release Messages
2930
2931   When the server receives a Release message via unicast from a client
2932   to which the server has not sent a unicast option, the server
2933   discards the Release message and responds with a Reply message
2934   containing a Status Code option with value UseMulticast, a Server
2935   Identifier option containing the server's DUID, the Client Identifier
2936   option from the client message, and no other options.
2937
2938   Upon the receipt of a valid Release message, the server examines the
2939   IAs and the addresses in the IAs for validity.  If the IAs in the
2940   message are in a binding for the client, and the addresses in the IAs
2941   have been assigned by the server to those IAs, the server deletes the
2942   addresses from the IAs and makes the addresses available for
2943   assignment to other clients.  The server ignores addresses not
2944   assigned to the IA, although it may choose to log an error.
2945
2946   After all the addresses have been processed, the server generates a
2947   Reply message and includes a Status Code option with value Success, a
2948   Server Identifier option with the server's DUID, and a Client
2949   Identifier option with the client's DUID.  For each IA in the Release
2950   message for which the server has no binding information, the server
2951   adds an IA option using the IAID from the Release message, and
2952   includes a Status Code option with the value NoBinding in the IA
2953   option.  No other options are included in the IA option.
2954
2955   A server may choose to retain a record of assigned addresses and IAs
2956   after the lifetimes on the addresses have expired to allow the server
2957   to reassign the previously assigned addresses to a client.
2958
295918.2.7. Receipt of Decline Messages
2960
2961   When the server receives a Decline message via unicast from a client
2962   to which the server has not sent a unicast option, the server
2963   discards the Decline message and responds with a Reply message
2964   containing a Status Code option with the value UseMulticast, a Server
2965   Identifier option containing the server's DUID, the Client Identifier
2966   option from the client message, and no other options.
2967
2968
2969
2970Droms, et al.               Standards Track                    [Page 53]
2971
2972RFC 3315                     DHCP for IPv6                     July 2003
2973
2974
2975   Upon the receipt of a valid Decline message, the server examines the
2976   IAs and the addresses in the IAs for validity.  If the IAs in the
2977   message are in a binding for the client, and the addresses in the IAs
2978   have been assigned by the server to those IAs, the server deletes the
2979   addresses from the IAs.  The server ignores addresses not assigned to
2980   the IA (though it may choose to log an error if it finds such an
2981   address).
2982
2983   The client has found any addresses in the Decline messages to be
2984   already in use on its link.  Therefore, the server SHOULD mark the
2985   addresses declined by the client so that those addresses are not
2986   assigned to other clients, and MAY choose to make a notification that
2987   addresses were declined.  Local policy on the server determines when
2988   the addresses identified in a Decline message may be made available
2989   for assignment.
2990
2991   After all the addresses have been processed, the server generates a
2992   Reply message and includes a Status Code option with the value
2993   Success, a Server Identifier option with the server's DUID, and a
2994   Client Identifier option with the client's DUID.  For each IA in the
2995   Decline message for which the server has no binding information, the
2996   server adds an IA option using the IAID from the Release message and
2997   includes a Status Code option with the value NoBinding in the IA
2998   option.  No other options are included in the IA option.
2999
300018.2.8. Transmission of Reply Messages
3001
3002   If the original message was received directly by the server, the
3003   server unicasts the Reply message directly to the client using the
3004   address in the source address field from the IP datagram in which the
3005   original message was received.  The Reply message MUST be unicast
3006   through the interface on which the original message was received.
3007
3008   If the original message was received in a Relay-forward message, the
3009   server constructs a Relay-reply message with the Reply message in the
3010   payload of a Relay Message option (see section 22.10).  If the
3011   Relay-forward messages included an Interface-id option, the server
3012   copies that option to the Relay-reply message.  The server unicasts
3013   the Relay-reply message directly to the relay agent using the address
3014   in the source address field from the IP datagram in which the
3015   Relay-forward message was received.
3016
301719. DHCP Server-Initiated Configuration Exchange
3018
3019   A server initiates a configuration exchange to cause DHCP clients to
3020   obtain new addresses and other configuration information.  For
3021   example, an administrator may use a server-initiated configuration
3022   exchange when links in the DHCP domain are to be renumbered.  Other
3023
3024
3025
3026Droms, et al.               Standards Track                    [Page 54]
3027
3028RFC 3315                     DHCP for IPv6                     July 2003
3029
3030
3031   examples include changes in the location of directory servers,
3032   addition of new services such as printing, and availability of new
3033   software.
3034
303519.1. Server Behavior
3036
3037   A server sends a Reconfigure message to cause a client to initiate
3038   immediately a Renew/Reply or Information-request/Reply message
3039   exchange with the server.
3040
304119.1.1. Creation and Transmission of Reconfigure Messages
3042
3043   The server sets the "msg-type" field to RECONFIGURE.  The server sets
3044   the transaction-id field to 0.  The server includes a Server
3045   Identifier option containing its DUID and a Client Identifier option
3046   containing the client's DUID in the Reconfigure message.
3047
3048   The server MAY include an Option Request option to inform the client
3049   of what information has been changed or new information that has been
3050   added.  In particular, the server specifies the IA option in the
3051   Option Request option if the server wants the client to obtain new
3052   address information.  If the server identifies the IA option in the
3053   Option Request option, the server MUST include an IA option that
3054   contains no other sub-options to identify each IA that is to be
3055   reconfigured on the client.
3056
3057   Because of the risk of denial of service attacks against DHCP
3058   clients, the use of a security mechanism is mandated in Reconfigure
3059   messages.  The server MUST use DHCP authentication in the Reconfigure
3060   message.
3061
3062   The server MUST include a Reconfigure Message option (defined in
3063   section 22.19) to select whether the client responds with a Renew
3064   message or an Information-Request message.
3065
3066   The server MUST NOT include any other options in the Reconfigure
3067   except as specifically allowed in the definition of individual
3068   options.
3069
3070   A server sends each Reconfigure message to a single DHCP client,
3071   using an IPv6 unicast address of sufficient scope belonging to the
3072   DHCP client.  If the server does not have an address to which it can
3073   send the Reconfigure message directly to the client, the server uses
3074   a Relay-reply message (as described in section 20.3) to send the
3075   Reconfigure message to a relay agent that will relay the message to
3076   the client.  The server may obtain the address of the client (and the
3077
3078
3079
3080
3081
3082Droms, et al.               Standards Track                    [Page 55]
3083
3084RFC 3315                     DHCP for IPv6                     July 2003
3085
3086
3087   appropriate relay agent, if required) through the information the
3088   server has about clients that have been in contact with the server,
3089   or through some external agent.
3090
3091   To reconfigure more than one client, the server unicasts a separate
3092   message to each client.  The server may initiate the reconfiguration
3093   of multiple clients concurrently; for example, a server may send a
3094   Reconfigure message to additional clients while previous
3095   reconfiguration message exchanges are still in progress.
3096
3097   The Reconfigure message causes the client to initiate a Renew/Reply
3098   or Information-request/Reply message exchange with the server.  The
3099   server interprets the receipt of a Renew or Information-request
3100   message (whichever was specified in the original Reconfigure message)
3101   from the client as satisfying the Reconfigure message request.
3102
310319.1.2. Time Out and Retransmission of Reconfigure Messages
3104
3105   If the server does not receive a Renew or Information-request message
3106   from the client in REC_TIMEOUT milliseconds, the server retransmits
3107   the Reconfigure message, doubles the REC_TIMEOUT value and waits
3108   again.  The server continues this process until REC_MAX_RC
3109   unsuccessful attempts have been made, at which point the server
3110   SHOULD abort the reconfigure process for that client.
3111
3112   Default and initial values for REC_TIMEOUT and REC_MAX_RC are
3113   documented in section 5.5.
3114
311519.2. Receipt of Renew Messages
3116
3117   The server generates and sends a Reply message to the client as
3118   described in sections 18.2.3 and 18.2.8, including options for
3119   configuration parameters.
3120
3121   The server MAY include options containing the IAs and new values for
3122   other configuration parameters in the Reply message, even if those
3123   IAs and parameters were not requested in the Renew message from the
3124   client.
3125
312619.3. Receipt of Information-request Messages
3127
3128   The server generates and sends a Reply message to the client as
3129   described in sections 18.2.5 and 18.2.8, including options for
3130   configuration parameters.
3131
3132
3133
3134
3135
3136
3137
3138Droms, et al.               Standards Track                    [Page 56]
3139
3140RFC 3315                     DHCP for IPv6                     July 2003
3141
3142
3143   The server MAY include options containing new values for other
3144   configuration parameters in the Reply message, even if those
3145   parameters were not requested in the Information-request message from
3146   the client.
3147
314819.4. Client Behavior
3149
3150   A client receives Reconfigure messages sent to the UDP port 546 on
3151   interfaces for which it has acquired configuration information
3152   through DHCP.  These messages may be sent at any time.  Since the
3153   results of a reconfiguration event may affect application layer
3154   programs, the client SHOULD log these events, and MAY notify these
3155   programs of the change through an implementation-specific interface.
3156
315719.4.1. Receipt of Reconfigure Messages
3158
3159   Upon receipt of a valid Reconfigure message, the client responds with
3160   either a Renew message or an Information-request message as indicated
3161   by the Reconfigure Message option (as defined in section 22.19).  The
3162   client ignores the transaction-id field in the received Reconfigure
3163   message.  While the transaction is in progress, the client silently
3164   discards any Reconfigure messages it receives.
3165
3166   DISCUSSION:
3167
3168      The Reconfigure message acts as a trigger that signals the client
3169      to complete a successful message exchange.  Once the client has
3170      received a Reconfigure, the client proceeds with the message
3171      exchange (retransmitting the Renew or Information-request message
3172      if necessary); the client ignores any additional Reconfigure
3173      messages until the exchange is complete.  Subsequent Reconfigure
3174      messages cause the client to initiate a new exchange.
3175
3176      How does this mechanism work in the face of duplicated or
3177      retransmitted Reconfigure messages?  Duplicate messages will be
3178      ignored because the client will begin the exchange after the
3179      receipt of the first Reconfigure.  Retransmitted messages will
3180      either trigger the exchange (if the first Reconfigure was not
3181      received by the client) or will be ignored.  The server can
3182      discontinue retransmission of Reconfigure messages to the client
3183      once the server receives the Renew or Information-request message
3184      from the client.
3185
3186      It might be possible for a duplicate or retransmitted Reconfigure
3187      to be sufficiently delayed (and delivered out of order) to arrive
3188      at the client after the exchange (initiated by the original
3189      Reconfigure) has been completed.  In this case, the client would
3190      initiate a redundant exchange.  The likelihood of delayed and out
3191
3192
3193
3194Droms, et al.               Standards Track                    [Page 57]
3195
3196RFC 3315                     DHCP for IPv6                     July 2003
3197
3198
3199      of order delivery is small enough to be ignored.  The consequence
3200      of the redundant exchange is inefficiency rather than incorrect
3201      operation.
3202
320319.4.2. Creation and Transmission of Renew Messages
3204
3205   When responding to a Reconfigure, the client creates and sends the
3206   Renew message in exactly the same manner as outlined in section
3207   18.1.3, with the exception that the client copies the Option Request
3208   option and any IA options from the Reconfigure message into the Renew
3209   message.
3210
321119.4.3. Creation and Transmission of Information-request Messages
3212
3213   When responding to a Reconfigure, the client creates and sends the
3214   Information-request message in exactly the same manner as outlined in
3215   section 18.1.5, with the exception that the client includes a Server
3216   Identifier option with the identifier from the Reconfigure message to
3217   which the client is responding.
3218
321919.4.4. Time Out and Retransmission of Renew or Information-request
3220        Messages
3221
3222   The client uses the same variables and retransmission algorithm as it
3223   does with Renew or Information-request messages generated as part of
3224   a client-initiated configuration exchange.  See sections 18.1.3 and
3225   18.1.5 for details.  If the client does not receive a response from
3226   the server by the end of the retransmission process, the client
3227   ignores and discards the Reconfigure message.
3228
322919.4.5. Receipt of Reply Messages
3230
3231   Upon the receipt of a valid Reply message, the client processes the
3232   options and sets (or resets) configuration parameters appropriately.
3233   The client records and updates the lifetimes for any addresses
3234   specified in IAs in the Reply message.
3235
323620. Relay Agent Behavior
3237
3238   The relay agent MAY be configured to use a list of destination
3239   addresses, which MAY include unicast addresses, the All_DHCP_Servers
3240   multicast address, or other addresses selected by the network
3241   administrator.  If the relay agent has not been explicitly
3242   configured, it MUST use the All_DHCP_Servers multicast address as the
3243   default.
3244
3245
3246
3247
3248
3249
3250Droms, et al.               Standards Track                    [Page 58]
3251
3252RFC 3315                     DHCP for IPv6                     July 2003
3253
3254
3255   If the relay agent relays messages to the All_DHCP_Servers multicast
3256   address or other multicast addresses, it sets the Hop Limit field to
3257   32.
3258
325920.1. Relaying a Client Message or a Relay-forward Message
3260
3261   A relay agent relays both messages from clients and Relay-forward
3262   messages from other relay agents.  When a relay agent receives a
3263   valid message to be relayed, it constructs a new Relay-forward
3264   message.  The relay agent copies the source address from the header
3265   of the IP datagram in which the message was received to the
3266   peer-address field of the Relay-forward message.  The relay agent
3267   copies the received DHCP message (excluding any IP or UDP headers)
3268   into a Relay Message option in the new message.  The relay agent adds
3269   to the Relay-forward message any other options it is configured to
3270   include.
3271
327220.1.1. Relaying a Message from a Client
3273
3274   If the relay agent received the message to be relayed from a client,
3275   the relay agent places a global or site-scoped address with a prefix
3276   assigned to the link on which the client should be assigned an
3277   address in the link-address field.  This address will be used by the
3278   server to determine the link from which the client should be assigned
3279   an address and other configuration information.  The hop-count in the
3280   Relay-forward message is set to 0.
3281
3282   If the relay agent cannot use the address in the link-address field
3283   to identify the interface through which the response to the client
3284   will be relayed, the relay agent MUST include an Interface-id option
3285   (see section 22.18) in the Relay-forward message.  The server will
3286   include the Interface-id option in its Relay-reply message.  The
3287   relay agent fills in the link-address field as described in the
3288   previous paragraph regardless of whether the relay agent includes an
3289   Interface-id option in the Relay-forward message.
3290
329120.1.2. Relaying a Message from a Relay Agent
3292
3293   If the message received by the relay agent is a Relay-forward message
3294   and the hop-count in the message is greater than or equal to
3295   HOP_COUNT_LIMIT, the relay agent discards the received message.
3296
3297   The relay agent copies the source address from the IP datagram in
3298   which the message was received from the client into the peer-address
3299   field in the Relay-forward message and sets the hop-count field to
3300   the value of the hop-count field in the received message incremented
3301   by 1.
3302
3303
3304
3305
3306Droms, et al.               Standards Track                    [Page 59]
3307
3308RFC 3315                     DHCP for IPv6                     July 2003
3309
3310
3311   If the source address from the IP datagram header of the received
3312   message is a global or site-local address (and the device on which
3313   the relay agent is running belongs to only one site), the relay agent
3314   sets the link-address field to 0; otherwise the relay agent sets the
3315   link-address field to a global or site-local address assigned to the
3316   interface on which the message was received, or includes an
3317   Interface-ID option to identify the interface on which the message
3318   was received.
3319
332020.2. Relaying a Relay-reply Message
3321
3322   The relay agent processes any options included in the Relay-reply
3323   message in addition to the Relay Message option, and then discards
3324   those options.
3325
3326   The relay agent extracts the message from the Relay Message option
3327   and relays it to the address contained in the peer-address field of
3328   the Relay-reply message.
3329
3330   If the Relay-reply message includes an Interface-id option, the relay
3331   agent relays the message from the server to the client on the link
3332   identified by the Interface-id option.  Otherwise, if the
3333   link-address field is not set to zero, the relay agent relays the
3334   message on the link identified by the link-address field.
3335
333620.3. Construction of Relay-reply Messages
3337
3338   A server uses a Relay-reply message to return a response to a client
3339   if the original message from the client was relayed to the server in
3340   a Relay-forward message or to send a Reconfigure message to a client
3341   if the server does not have an address it can use to send the message
3342   directly to the client.
3343
3344   A response to the client MUST be relayed through the same relay
3345   agents as the original client message.  The server causes this to
3346   happen by creating a Relay-reply message that includes a Relay
3347   Message option containing the message for the next relay agent in the
3348   return path to the client.  The contained Relay-reply message
3349   contains another Relay Message option to be sent to the next relay
3350   agent, and so on.  The server must record the contents of the
3351   peer-address fields in the received message so it can construct the
3352   appropriate Relay-reply message carrying the response from the
3353   server.
3354
3355
3356
3357
3358
3359
3360
3361
3362Droms, et al.               Standards Track                    [Page 60]
3363
3364RFC 3315                     DHCP for IPv6                     July 2003
3365
3366
3367   For example, if client C sent a message that was relayed by relay
3368   agent A to relay agent B and then to the server, the server would
3369   send the following Relay-Reply message to relay agent B:
3370
3371   msg-type:       RELAY-REPLY
3372   hop-count:      1
3373   link-address:   0
3374   peer-address:   A
3375   Relay Message option, containing:
3376     msg-type:     RELAY-REPLY
3377     hop-count:    0
3378     link-address: address from link to which C is attached
3379     peer-address: C
3380     Relay Message option: <response from server>
3381
3382   When sending a Reconfigure message to a client through a relay agent,
3383   the server creates a Relay-reply message that includes a Relay
3384   Message option containing the Reconfigure message for the next relay
3385   agent in the return path to the client.  The server sets the
3386   peer-address field in the Relay-reply message header to the address
3387   of the client, and sets the link-address field as required by the
3388   relay agent to relay the Reconfigure message to the client.  The
3389   server obtains the addresses of the client and the relay agent
3390   through prior interaction with the client or through some external
3391   mechanism.
3392
339321. Authentication of DHCP Messages
3394
3395   Some network administrators may wish to provide authentication of the
3396   source and contents of DHCP messages.  For example, clients may be
3397   subject to denial of service attacks through the use of bogus DHCP
3398   servers, or may simply be misconfigured due to unintentionally
3399   instantiated DHCP servers.  Network administrators may wish to
3400   constrain the allocation of addresses to authorized hosts to avoid
3401   denial of service attacks in "hostile" environments where the network
3402   medium is not physically secured, such as wireless networks or
3403   college residence halls.
3404
3405   The DHCP authentication mechanism is based on the design of
3406   authentication for DHCPv4 [4].
3407
340821.1. Security of Messages Sent Between Servers and Relay Agents
3409
3410   Relay agents and servers that exchange messages securely use the
3411   IPsec mechanisms for IPv6 [7].  If a client message is relayed
3412   through multiple relay agents, each of the relay agents must have
3413   established independent, pairwise trust relationships.  That is, if
3414   messages from client C will be relayed by relay agent A to relay
3415
3416
3417
3418Droms, et al.               Standards Track                    [Page 61]
3419
3420RFC 3315                     DHCP for IPv6                     July 2003
3421
3422
3423   agent B and then to the server, relay agents A and B must be
3424   configured to use IPSec for the messages they exchange, and relay
3425   agent B and the server must be configured to use IPSec for the
3426   messages they exchange.
3427
3428   Relay agents and servers that support secure relay agent to server or
3429   relay agent to relay agent communication use IPsec under the
3430   following conditions:
3431
3432      Selectors        Relay agents are manually configured with the
3433                       addresses of the relay agent or server to which
3434                       DHCP messages are to be forwarded.  Each relay
3435                       agent and server that will be using IPsec for
3436                       securing DHCP messages must also be configured
3437                       with a list of the relay agents to which messages
3438                       will be returned.  The selectors for the relay
3439                       agents and servers will be the pairs of addresses
3440                       defining relay agents and servers that exchange
3441                       DHCP messages on the DHCPv6 UDP ports 546 and
3442                       547.
3443
3444      Mode             Relay agents and servers use transport mode and
3445                       ESP. The information in DHCP messages is not
3446                       generally considered confidential, so encryption
3447                       need not be used (i.e., NULL encryption can be
3448                       used).
3449
3450      Key management   Because the relay agents and servers are used
3451                       within an organization, public key schemes are
3452                       not necessary.  Because the relay agents and
3453                       servers must be manually configured, manually
3454                       configured key management may suffice, but does
3455                       not provide defense against replayed messages.
3456                       Accordingly, IKE with preshared secrets SHOULD be
3457                       supported.  IKE with public keys MAY be
3458                       supported.
3459
3460      Security policy  DHCP messages between relay agents and servers
3461                       should only be accepted from DHCP peers as
3462                       identified in the local configuration.
3463
3464      Authentication   Shared keys, indexed to the source IP address of
3465                       the received DHCP message, are adequate in this
3466                       application.
3467
3468      Availability     Appropriate IPsec implementations are likely to
3469                       be available for servers and for relay agents in
3470                       more featureful devices used in enterprise and
3471
3472
3473
3474Droms, et al.               Standards Track                    [Page 62]
3475
3476RFC 3315                     DHCP for IPv6                     July 2003
3477
3478
3479                       core ISP networks.  IPsec is less likely to be
3480                       available for relay agents in low end devices
3481                       primarily used in the home or small office
3482                       markets.
3483
348421.2. Summary of DHCP Authentication
3485
3486   Authentication of DHCP messages is accomplished through the use of
3487   the Authentication option (see section 22.11).  The authentication
3488   information carried in the Authentication option can be used to
3489   reliably identify the source of a DHCP message and to confirm that
3490   the contents of the DHCP message have not been tampered with.
3491
3492   The Authentication option provides a framework for multiple
3493   authentication protocols.  Two such protocols are defined here.
3494   Other protocols defined in the future will be specified in separate
3495   documents.
3496
3497   Any DHCP message MUST NOT include more than one Authentication
3498   option.
3499
3500   The protocol field in the Authentication option identifies the
3501   specific protocol used to generate the authentication information
3502   carried in the option.  The algorithm field identifies a specific
3503   algorithm within the authentication protocol; for example, the
3504   algorithm field specifies the hash algorithm used to generate the
3505   message authentication code (MAC) in the authentication option.  The
3506   replay detection method (RDM) field specifies the type of replay
3507   detection used in the replay detection field.
3508
350921.3. Replay Detection
3510
3511   The Replay Detection Method (RDM) field determines the type of replay
3512   detection used in the Replay Detection field.
3513
3514   If the RDM field contains 0x00, the replay detection field MUST be
3515   set to the value of a monotonically increasing counter.  Using a
3516   counter value, such as the current time of day (for example, an NTP-
3517   format timestamp [9]), can reduce the danger of replay attacks.  This
3518   method MUST be supported by all protocols.
3519
352021.4. Delayed Authentication Protocol
3521
3522   If the protocol field is 2, the message is using the "delayed
3523   authentication" mechanism.  In delayed authentication, the client
3524   requests authentication in its Solicit message, and the server
3525   replies with an Advertise message that includes authentication
3526
3527
3528
3529
3530Droms, et al.               Standards Track                    [Page 63]
3531
3532RFC 3315                     DHCP for IPv6                     July 2003
3533
3534
3535   information.  This authentication information contains a nonce value
3536   generated by the source as a message authentication code (MAC) to
3537   provide message authentication and entity authentication.
3538
3539   The use of a particular technique based on the HMAC protocol [8]
3540   using the MD5 hash [16] is defined here.
3541
354221.4.1. Use of the Authentication Option in the Delayed Authentication
3543        Protocol
3544
3545   In a Solicit message, the client fills in the protocol, algorithm and
3546   RDM fields in the Authentication option with the client's
3547   preferences.  The client sets the replay detection field to zero and
3548   omits the authentication information field.  The client sets the
3549   option-len field to 11.
3550
3551   In all other messages, the protocol and algorithm fields identify the
3552   method used to construct the contents of the authentication
3553   information field.  The RDM field identifies the method used to
3554   construct the contents of the replay detection field.
3555
3556   The format of the Authentication information is:
3557
3558     0                   1                   2                   3
3559     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
3560    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3561    |                          DHCP realm                           |
3562    |                      (variable length)                        |
3563    .                                                               .
3564    .                                                               .
3565    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3566    |                            key ID                             |
3567    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3568    |                                                               |
3569    |                           HMAC-MD5                            |
3570    |                          (128 bits)                           |
3571    |                                                               |
3572    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3573
3574      DHCP realm  The DHCP realm that identifies the key used to
3575                  generate the HMAC-MD5 value.
3576
3577      key ID      The key identifier that identified the key used to
3578                  generate the HMAC-MD5 value.
3579
3580      HMAC-MD5    The message authentication code generated by applying
3581                  MD5 to the DHCP message using the key identified by
3582                  the DHCP realm, client DUID, and key ID.
3583
3584
3585
3586Droms, et al.               Standards Track                    [Page 64]
3587
3588RFC 3315                     DHCP for IPv6                     July 2003
3589
3590
3591   The sender computes the MAC using the HMAC generation algorithm [8]
3592   and the MD5 hash function [16].  The entire DHCP message (setting the
3593   MAC field of the authentication option to zero), including the DHCP
3594   message header and the options field, is used as input to the HMAC-
3595   MD5 computation function.
3596
3597   DISCUSSION:
3598
3599      Algorithm 1 specifies the use of HMAC-MD5.  Use of a different
3600      technique, such as HMAC-SHA, will be specified as a separate
3601      protocol.
3602
3603      The DHCP realm used to identify authentication keys is chosen to
3604      be unique among administrative domains.  Use of the DHCP realm
3605      allows DHCP administrators to avoid conflict in the use of key
3606      identifiers, and allows a host using DHCP to use authenticated
3607      DHCP while roaming among DHCP administrative domains.
3608
360921.4.2. Message Validation
3610
3611   Any DHCP message that includes more than one authentication option
3612   MUST be discarded.
3613
3614   To validate an incoming message, the receiver first checks that the
3615   value in the replay detection field is acceptable according to the
3616   replay detection method specified by the RDM field.  Next, the
3617   receiver computes the MAC as described in [8].  The entire DHCP
3618   message (setting the MAC field of the authentication option to 0) is
3619   used as input to the HMAC-MD5 computation function.  If the MAC
3620   computed by the receiver does not match the MAC contained in the
3621   authentication option, the receiver MUST discard the DHCP message.
3622
362321.4.3. Key Utilization
3624
3625   Each DHCP client has a set of keys.  Each key is identified by <DHCP
3626   realm, client DUID, key id>.  Each key also has a lifetime.  The key
3627   may not be used past the end of its lifetime.  The client's keys are
3628   initially distributed to the client through some out-of-band
3629   mechanism.  The lifetime for each key is distributed with the key.
3630   Mechanisms for key distribution and lifetime specification are beyond
3631   the scope of this document.
3632
3633   The client and server use one of the client's keys to authenticate
3634   DHCP messages during a session (until the next Solicit message sent
3635   by the client).
3636
3637
3638
3639
3640
3641
3642Droms, et al.               Standards Track                    [Page 65]
3643
3644RFC 3315                     DHCP for IPv6                     July 2003
3645
3646
364721.4.4. Client Considerations for Delayed Authentication Protocol
3648
3649   The client announces its intention to use DHCP authentication by
3650   including an Authentication option in its Solicit message.  The
3651   server selects a key for the client based on the client's DUID.  The
3652   client and server use that key to authenticate all DHCP messages
3653   exchanged during the session.
3654
365521.4.4.1. Sending Solicit Messages
3656
3657   When the client sends a Solicit message and wishes to use
3658   authentication, it includes an Authentication option with the desired
3659   protocol, algorithm and RDM as described in section 21.4.  The client
3660   does not include any replay detection or authentication information
3661   in the Authentication option.
3662
366321.4.4.2. Receiving Advertise Messages
3664
3665   The client validates any Advertise messages containing an
3666   Authentication option specifying the delayed authentication protocol
3667   using the validation test described in section 21.4.2.
3668
3669   Client behavior, if no Advertise messages include authentication
3670   information or pass the validation test, is controlled by local
3671   policy on the client.  According to client policy, the client MAY
3672   choose to respond to an Advertise message that has not been
3673   authenticated.
3674
3675   The decision to set local policy to accept unauthenticated messages
3676   should be made with care.  Accepting an unauthenticated Advertise
3677   message can make the client vulnerable to spoofing and other attacks.
3678   If local users are not explicitly informed that the client has
3679   accepted an unauthenticated Advertise message, the users may
3680   incorrectly assume that the client has received an authenticated
3681   address and is not subject to DHCP attacks through unauthenticated
3682   messages.
3683
3684   A client MUST be configurable to discard unauthenticated messages,
3685   and SHOULD be configured by default to discard unauthenticated
3686   messages if the client has been configured with an authentication key
3687   or other authentication information.  A client MAY choose to
3688   differentiate between Advertise messages with no authentication
3689   information and Advertise messages that do not pass the validation
3690   test; for example, a client might accept the former and discard the
3691   latter.  If a client does accept an unauthenticated message, the
3692   client SHOULD inform any local users and SHOULD log the event.
3693
3694
3695
3696
3697
3698Droms, et al.               Standards Track                    [Page 66]
3699
3700RFC 3315                     DHCP for IPv6                     July 2003
3701
3702
370321.4.4.3. Sending Request, Confirm, Renew, Rebind, Decline or Release
3704          Messages
3705
3706   If the client authenticated the Advertise message through which the
3707   client selected the server, the client MUST generate authentication
3708   information for subsequent Request, Confirm, Renew, Rebind or Release
3709   messages sent to the server, as described in section 21.4.  When the
3710   client sends a subsequent message, it MUST use the same key used by
3711   the server to generate the authentication information.
3712
371321.4.4.4. Sending Information-request Messages
3714
3715   If the server has selected a key for the client in a previous message
3716   exchange (see section 21.4.5.1), the client MUST use the same key to
3717   generate the authentication information throughout the session.
3718
371921.4.4.5. Receiving Reply Messages
3720
3721   If the client authenticated the Advertise it accepted, the client
3722   MUST validate the associated Reply message from the server.  The
3723   client MUST discard the Reply if the message fails to pass the
3724   validation test and MAY log the validation failure.  If the Reply
3725   fails to pass the validation test, the client MUST restart the DHCP
3726   configuration process by sending a Solicit message.
3727
3728   If the client accepted an Advertise message that did not include
3729   authentication information or did not pass the validation test, the
3730   client MAY accept an unauthenticated Reply message from the server.
3731
373221.4.4.6. Receiving Reconfigure Messages
3733
3734   The client MUST discard the Reconfigure if the message fails to pass
3735   the validation test and MAY log the validation failure.
3736
373721.4.5. Server Considerations for Delayed Authentication Protocol
3738
3739   After receiving a Solicit message that contains an Authentication
3740   option, the server selects a key for the client, based on the
3741   client's DUID and key selection policies with which the server has
3742   been configured.  The server identifies the selected key in the
3743   Advertise message and uses the key to validate subsequent messages
3744   between the client and the server.
3745
3746
3747
3748
3749
3750
3751
3752
3753
3754Droms, et al.               Standards Track                    [Page 67]
3755
3756RFC 3315                     DHCP for IPv6                     July 2003
3757
3758
375921.4.5.1. Receiving Solicit Messages and Sending Advertise Messages
3760
3761   The server selects a key for the client and includes authentication
3762   information in the Advertise message returned to the client as
3763   specified in section 21.4.  The server MUST record the identifier of
3764   the key selected for the client and use that same key for validating
3765   subsequent messages with the client.
3766
376721.4.5.2. Receiving Request, Confirm, Renew, Rebind or Release Messages
3768          and Sending Reply Messages
3769
3770   The server uses the key identified in the message and validates the
3771   message as specified in section 21.4.2.  If the message fails to pass
3772   the validation test or the server does not know the key identified by
3773   the 'key ID' field, the server MUST discard the message and MAY
3774   choose to log the validation failure.
3775
3776   If the message passes the validation test, the server responds to the
3777   specific message as described in section 18.2.  The server MUST
3778   include authentication information generated using the key identified
3779   in the received message, as specified in section 21.4.
3780
378121.5. Reconfigure Key Authentication Protocol
3782
3783   The Reconfigure key authentication protocol provides protection
3784   against misconfiguration of a client caused by a Reconfigure message
3785   sent by a malicious DHCP server.  In this protocol, a DHCP server
3786   sends a Reconfigure Key to the client in the initial exchange of DHCP
3787   messages.  The client records the Reconfigure Key for use in
3788   authenticating subsequent Reconfigure messages from that server.  The
3789   server then includes an HMAC computed from the Reconfigure Key in
3790   subsequent Reconfigure messages.
3791
3792   Both the Reconfigure Key sent from the server to the client and the
3793   HMAC in subsequent Reconfigure messages are carried as the
3794   Authentication information in an Authentication option.  The format
3795   of the Authentication information is defined in the following
3796   section.
3797
3798   The Reconfigure Key protocol is used (initiated by the server) only
3799   if the client and server are not using any other authentication
3800   protocol and the client and server have negotiated to use Reconfigure
3801   messages.
3802
3803
3804
3805
3806
3807
3808
3809
3810Droms, et al.               Standards Track                    [Page 68]
3811
3812RFC 3315                     DHCP for IPv6                     July 2003
3813
3814
381521.5.1. Use of the Authentication Option in the Reconfigure Key
3816        Authentication Protocol
3817
3818   The following fields are set in an Authentication option for the
3819   Reconfigure Key Authentication Protocol:
3820
3821      protocol    3
3822
3823      algorithm   1
3824
3825      RDM         0
3826
3827   The format of the Authentication information for the Reconfigure Key
3828   Authentication Protocol is:
3829
3830     0                   1                   2                   3
3831     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
3832    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3833    |     Type      |                 Value (128 bits)              |
3834    +-+-+-+-+-+-+-+-+                                               |
3835    .                                                               .
3836    .                                                               .
3837    .                                               +-+-+-+-+-+-+-+-+
3838    |                                               |
3839    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3840
3841      Type    Type of data in Value field carried in this option:
3842
3843                 1   Reconfigure Key value (used in Reply message).
3844
3845                 2   HMAC-MD5 digest of the message (used in Reconfigure
3846                     message).
3847
3848      Value   Data as defined by field.
3849
385021.5.2. Server considerations for Reconfigure Key protocol
3851
3852   The server selects a Reconfigure Key for a client during the
3853   Request/Reply, Solicit/Reply or Information-request/Reply message
3854   exchange.  The server records the Reconfigure Key and transmits that
3855   key to the client in an Authentication option in the Reply message.
3856
3857   The Reconfigure Key is 128 bits long, and MUST be a cryptographically
3858   strong random or pseudo-random number that cannot easily be
3859   predicted.
3860
3861
3862
3863
3864
3865
3866Droms, et al.               Standards Track                    [Page 69]
3867
3868RFC 3315                     DHCP for IPv6                     July 2003
3869
3870
3871   To provide authentication for a Reconfigure message, the server
3872   selects a replay detection value according to the RDM selected by the
3873   server, and computes an HMAC-MD5 of the Reconfigure message using the
3874   Reconfigure Key for the client.  The server computes the HMAC-MD5
3875   over the entire DHCP Reconfigure message, including the
3876   Authentication option; the HMAC-MD5 field in the Authentication
3877   option is set to zero for the HMAC-MD5 computation.  The server
3878   includes the HMAC-MD5 in the authentication information field in an
3879   Authentication option included in the Reconfigure message sent to the
3880   client.
3881
388221.5.3. Client considerations for Reconfigure Key protocol
3883
3884   The client will receive a Reconfigure Key from the server in the
3885   initial Reply message from the server.  The client records the
3886   Reconfigure Key for use in authenticating subsequent Reconfigure
3887   messages.
3888
3889   To authenticate a Reconfigure message, the client computes an
3890   HMAC-MD5 over the DHCP Reconfigure message, using the Reconfigure Key
3891   received from the server.  If this computed HMAC-MD5 matches the
3892   value in the Authentication option, the client accepts the
3893   Reconfigure message.
3894
389522. DHCP Options
3896
3897   Options are used to carry additional information and parameters in
3898   DHCP messages.  Every option shares a common base format, as
3899   described in section 22.1.  All values in options are represented in
3900   network byte order.
3901
3902   This document describes the DHCP options defined as part of the base
3903   DHCP specification.  Other options may be defined in the future in
3904   separate documents.
3905
3906   Unless otherwise noted, each option may appear only in the options
3907   area of a DHCP message and may appear only once.  If an option does
3908   appear multiple times, each instance is considered separate and the
3909   data areas of the options MUST NOT be concatenated or otherwise
3910   combined.
3911
3912
3913
3914
3915
3916
3917
3918
3919
3920
3921
3922Droms, et al.               Standards Track                    [Page 70]
3923
3924RFC 3315                     DHCP for IPv6                     July 2003
3925
3926
392722.1. Format of DHCP Options
3928
3929   The format of DHCP options is:
3930
3931       0                   1                   2                   3
3932       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
3933      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3934      |          option-code          |           option-len          |
3935      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3936      |                          option-data                          |
3937      |                      (option-len octets)                      |
3938      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3939
3940      option-code   An unsigned integer identifying the specific option
3941                    type carried in this option.
3942
3943      option-len    An unsigned integer giving the length of the
3944                    option-data field in this option in octets.
3945
3946      option-data   The data for the option; the format of this data
3947                    depends on the definition of the option.
3948
3949   DHCPv6 options are scoped by using encapsulation.  Some options apply
3950   generally to the client, some are specific to an IA, and some are
3951   specific to the addresses within an IA.  These latter two cases are
3952   discussed in sections 22.4 and 22.6.
3953
395422.2. Client Identifier Option
3955
3956   The Client Identifier option is used to carry a DUID (see section 9)
3957   identifying a client between a client and a server.  The format of
3958   the Client Identifier option is:
3959
3960       0                   1                   2                   3
3961       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
3962      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3963      |        OPTION_CLIENTID        |          option-len           |
3964      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3965      .                                                               .
3966      .                              DUID                             .
3967      .                        (variable length)                      .
3968      .                                                               .
3969      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3970
3971      option-code   OPTION_CLIENTID (1).
3972
3973      option-len    Length of DUID in octets.
3974
3975
3976
3977
3978Droms, et al.               Standards Track                    [Page 71]
3979
3980RFC 3315                     DHCP for IPv6                     July 2003
3981
3982
3983      DUID          The DUID for the client.
3984
398522.3. Server Identifier Option
3986
3987   The Server Identifier option is used to carry a DUID (see section 9)
3988   identifying a server between a client and a server.  The format of
3989   the Server Identifier option is:
3990
3991       0                   1                   2                   3
3992       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
3993      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3994      |        OPTION_SERVERID        |          option-len           |
3995      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3996      .                                                               .
3997      .                              DUID                             .
3998      .                        (variable length)                      .
3999      .                                                               .
4000      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4001
4002      option-code   OPTION_SERVERID (2).
4003
4004      option-len    Length of DUID in octets.
4005
4006      DUID          The DUID for the server.
4007
400822.4. Identity Association for Non-temporary Addresses Option
4009
4010   The Identity Association for Non-temporary Addresses option (IA_NA
4011   option) is used to carry an IA_NA, the parameters associated with the
4012   IA_NA, and the non-temporary addresses associated with the IA_NA.
4013
4014   Addresses appearing in an IA_NA option are not temporary addresses
4015   (see section 22.5).
4016
4017
4018
4019
4020
4021
4022
4023
4024
4025
4026
4027
4028
4029
4030
4031
4032
4033
4034Droms, et al.               Standards Track                    [Page 72]
4035
4036RFC 3315                     DHCP for IPv6                     July 2003
4037
4038
4039   The format of the IA_NA option is:
4040
4041       0                   1                   2                   3
4042       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4043      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4044      |          OPTION_IA_NA         |          option-len           |
4045      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4046      |                        IAID (4 octets)                        |
4047      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4048      |                              T1                               |
4049      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4050      |                              T2                               |
4051      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4052      |                                                               |
4053      .                         IA_NA-options                         .
4054      .                                                               .
4055      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4056
4057      option-code          OPTION_IA_NA (3).
4058
4059      option-len           12 + length of IA_NA-options field.
4060
4061      IAID                 The unique identifier for this IA_NA; the
4062                           IAID must be unique among the identifiers for
4063                           all of this client's IA_NAs.  The number
4064                           space for IA_NA IAIDs is separate from the
4065                           number space for IA_TA IAIDs.
4066
4067      T1                   The time at which the client contacts the
4068                           server from which the addresses in the IA_NA
4069                           were obtained to extend the lifetimes of the
4070                           addresses assigned to the IA_NA; T1 is a
4071                           time duration relative to the current time
4072                           expressed in units of seconds.
4073
4074      T2                   The time at which the client contacts any
4075                           available server to extend the lifetimes of
4076                           the addresses assigned to the IA_NA; T2 is a
4077                           time duration relative to the current time
4078                           expressed in units of seconds.
4079
4080      IA_NA-options        Options associated with this IA_NA.
4081
4082   The IA_NA-options field encapsulates those options that are specific
4083   to this IA_NA.  For example, all of the IA Address Options carrying
4084   the addresses associated with this IA_NA are in the IA_NA-options
4085   field.
4086
4087
4088
4089
4090Droms, et al.               Standards Track                    [Page 73]
4091
4092RFC 3315                     DHCP for IPv6                     July 2003
4093
4094
4095   An IA_NA option may only appear in the options area of a DHCP
4096   message.  A DHCP message may contain multiple IA_NA options.
4097
4098   The status of any operations involving this IA_NA is indicated in a
4099   Status Code option in the IA_NA-options field.
4100
4101   Note that an IA_NA has no explicit "lifetime" or "lease length" of
4102   its own.  When the valid lifetimes of all of the addresses in an
4103   IA_NA have expired, the IA_NA can be considered as having expired.
4104   T1 and T2 are included to give servers explicit control over when a
4105   client recontacts the server about a specific IA_NA.
4106
4107   In a message sent by a client to a server, values in the T1 and T2
4108   fields indicate the client's preference for those parameters.  The
4109   client sets T1 and T2 to 0 if it has no preference for those values.
4110   In a message sent by a server to a client, the client MUST use the
4111   values in the T1 and T2 fields for the T1 and T2 parameters, unless
4112   those values in those fields are 0.  The values in the T1 and T2
4113   fields are the number of seconds until T1 and T2.
4114
4115   The server selects the T1 and T2 times to allow the client to extend
4116   the lifetimes of any addresses in the IA_NA before the lifetimes
4117   expire, even if the server is unavailable for some short period of
4118   time.  Recommended values for T1 and T2 are .5 and .8 times the
4119   shortest preferred lifetime of the addresses in the IA that the
4120   server is willing to extend, respectively.  If the "shortest"
4121   preferred lifetime is 0xffffffff ("infinity"), the recommended T1 and
4122   T2 values are also 0xffffffff.  If the time at which the addresses in
4123   an IA_NA are to be renewed is to be left to the discretion of the
4124   client, the server sets T1 and T2 to 0.
4125
4126   If a server receives an IA_NA with T1 greater than T2, and both T1
4127   and T2 are greater than 0, the server ignores the invalid values of
4128   T1 and T2 and processes the IA_NA as though the client had set T1 and
4129   T2 to 0.
4130
4131   If a client receives an IA_NA with T1 greater than T2, and both T1
4132   and T2 are greater than 0, the client discards the IA_NA option and
4133   processes the remainder of the message as though the server had not
4134   included the invalid IA_NA option.
4135
4136   Care should be taken in setting T1 or T2 to 0xffffffff ("infinity").
4137   A client will never attempt to extend the lifetimes of any addresses
4138   in an IA with T1 set to 0xffffffff.  A client will never attempt to
4139   use a Rebind message to locate a different server to extend the
4140   lifetimes of any addresses in an IA with T2 set to 0xffffffff.
4141
4142
4143
4144
4145
4146Droms, et al.               Standards Track                    [Page 74]
4147
4148RFC 3315                     DHCP for IPv6                     July 2003
4149
4150
415122.5. Identity Association for Temporary Addresses Option
4152
4153   The Identity Association for the Temporary Addresses (IA_TA) option
4154   is used to carry an IA_TA, the parameters associated with the IA_TA
4155   and the addresses associated with the IA_TA.  All of the addresses in
4156   this option are used by the client as temporary addresses, as defined
4157   in RFC 3041 [12].  The format of the IA_TA option is:
4158
4159       0                   1                   2                   3
4160       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4161      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4162      |         OPTION_IA_TA          |          option-len           |
4163      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4164      |                        IAID (4 octets)                        |
4165      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4166      |                                                               |
4167      .                         IA_TA-options                         .
4168      .                                                               .
4169      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4170
4171      option-code          OPTION_IA_TA (4).
4172
4173      option-len           4 + length of IA_TA-options field.
4174
4175      IAID                 The unique identifier for this IA_TA; the
4176                           IAID must be unique among the identifiers
4177                           for all of this client's IA_TAs.  The number
4178                           space for IA_TA IAIDs is separate from the
4179                           number space for IA_NA IAIDs.
4180
4181      IA_TA-options        Options associated with this IA_TA.
4182
4183   The IA_TA-Options field encapsulates those options that are specific
4184   to this IA_TA.  For example, all of the IA Address Options carrying
4185   the addresses associated with this IA_TA are in the IA_TA-options
4186   field.
4187
4188   Each IA_TA carries one "set" of temporary addresses; that is, at most
4189   one address from each prefix assigned to the link to which the client
4190   is attached.
4191
4192   An IA_TA option may only appear in the options area of a DHCP
4193   message.  A DHCP message may contain multiple IA_TA options.
4194
4195   The status of any operations involving this IA_TA is indicated in a
4196   Status Code option in the IA_TA-options field.
4197
4198
4199
4200
4201
4202Droms, et al.               Standards Track                    [Page 75]
4203
4204RFC 3315                     DHCP for IPv6                     July 2003
4205
4206
4207   Note that an IA has no explicit "lifetime" or "lease length" of its
4208   own.  When the valid lifetimes of all of the addresses in an IA_TA
4209   have expired, the IA can be considered as having expired.
4210
4211   An IA_TA option does not include values for T1 and T2.  A client MAY
4212   request that the lifetimes on temporary addresses be extended by
4213   including the addresses in a IA_TA option sent in a Renew or Rebind
4214   message to a server.  For example, a client would request an
4215   extension on the lifetime of a temporary address to allow an
4216   application to continue to use an established TCP connection.
4217
4218   The client obtains new temporary addresses by sending an IA_TA option
4219   with a new IAID to a server.  Requesting new temporary addresses from
4220   the server is the equivalent of generating new temporary addresses as
4221   described in RFC 3041.  The server will generate new temporary
4222   addresses and return them to the client.  The client should request
4223   new temporary addresses before the lifetimes on the previously
4224   assigned addresses expire.
4225
4226   A server MUST return the same set of temporary address for the same
4227   IA_TA (as identified by the IAID) as long as those addresses are
4228   still valid.  After the lifetimes of the addresses in an IA_TA have
4229   expired, the IAID may be reused to identify a new IA_TA with new
4230   temporary addresses.
4231
4232   This option MAY appear in a Confirm message if the lifetimes on the
4233   temporary addresses in the associated IA have not expired.
4234
423522.6. IA Address Option
4236
4237   The IA Address option is used to specify IPv6 addresses associated
4238   with an IA_NA or an IA_TA.  The IA Address option must be
4239   encapsulated in the Options field of an IA_NA or IA_TA option.  The
4240   Options field encapsulates those options that are specific to this
4241   address.
4242
4243
4244
4245
4246
4247
4248
4249
4250
4251
4252
4253
4254
4255
4256
4257
4258Droms, et al.               Standards Track                    [Page 76]
4259
4260RFC 3315                     DHCP for IPv6                     July 2003
4261
4262
4263   The format of the IA Address option is:
4264
4265       0                   1                   2                   3
4266       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4267      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4268      |          OPTION_IAADDR        |          option-len           |
4269      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4270      |                                                               |
4271      |                         IPv6 address                          |
4272      |                                                               |
4273      |                                                               |
4274      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4275      |                      preferred-lifetime                       |
4276      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4277      |                        valid-lifetime                         |
4278      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4279      .                                                               .
4280      .                        IAaddr-options                         .
4281      .                                                               .
4282      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4283
4284      option-code   OPTION_IAADDR (5).
4285
4286      option-len    24 + length of IAaddr-options field.
4287
4288      IPv6 address  An IPv6 address.
4289
4290      preferred-lifetime The preferred lifetime for the IPv6 address in
4291                    the option, expressed in units of seconds.
4292
4293      valid-lifetime The valid lifetime for the IPv6 address in the
4294                    option, expressed in units of seconds.
4295
4296      IAaddr-options Options associated with this address.
4297
4298   In a message sent by a client to a server, values in the preferred
4299   and valid lifetime fields indicate the client's preference for those
4300   parameters.  The client may send 0 if it has no preference for the
4301   preferred and valid lifetimes.  In a message sent by a server to a
4302   client, the client MUST use the values in the preferred and valid
4303   lifetime fields for the preferred and valid lifetimes.  The values in
4304   the preferred and valid lifetimes are the number of seconds remaining
4305   in each lifetime.
4306
4307
4308
4309
4310
4311
4312
4313
4314Droms, et al.               Standards Track                    [Page 77]
4315
4316RFC 3315                     DHCP for IPv6                     July 2003
4317
4318
4319   A client discards any addresses for which the preferred lifetime is
4320   greater than the valid lifetime.  A server ignores the lifetimes set
4321   by the client if the preferred lifetime is greater than the valid
4322   lifetime and ignores the values for T1 and T2 set by the client if
4323   those values are greater than the preferred lifetime.
4324
4325   Care should be taken in setting the valid lifetime of an address to
4326   0xffffffff ("infinity"), which amounts to a permanent assignment of
4327   an address to a client.
4328
4329   An IA Address option may appear only in an IA_NA option or an IA_TA
4330   option.  More than one IA Address Option can appear in an IA_NA
4331   option or an IA_TA option.
4332
4333   The status of any operations involving this IA Address is indicated
4334   in a Status Code option in the IAaddr-options field.
4335
433622.7. Option Request Option
4337
4338   The Option Request option is used to identify a list of options in a
4339   message between a client and a server.  The format of the Option
4340   Request option is:
4341
4342       0                   1                   2                   3
4343       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4344      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4345      |           OPTION_ORO          |           option-len          |
4346      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4347      |    requested-option-code-1    |    requested-option-code-2    |
4348      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4349      |                              ...                              |
4350      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4351
4352      option-code   OPTION_ORO (6).
4353
4354      option-len    2 * number of requested options.
4355
4356      requested-option-code-n The option code for an option requested by
4357                    the client.
4358
4359   A client MAY include an Option Request option in a Solicit, Request,
4360   Renew, Rebind, Confirm or Information-request message to inform the
4361   server about options the client wants the server to send to the
4362   client.  A server MAY include an Option Request option in a
4363   Reconfigure option to indicate which options the client should
4364   request from the server.
4365
4366
4367
4368
4369
4370Droms, et al.               Standards Track                    [Page 78]
4371
4372RFC 3315                     DHCP for IPv6                     July 2003
4373
4374
437522.8. Preference Option
4376
4377   The Preference option is sent by a server to a client to affect the
4378   selection of a server by the client.
4379
4380   The format of the Preference option is:
4381
4382       0                   1                   2                   3
4383       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4384      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4385      |       OPTION_PREFERENCE       |          option-len           |
4386      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4387      |  pref-value   |
4388      +-+-+-+-+-+-+-+-+
4389
4390      option-code   OPTION_PREFERENCE (7).
4391
4392      option-len    1.
4393
4394      pref-value    The preference value for the server in this message.
4395
4396   A server MAY include a Preference option in an Advertise message to
4397   control the selection of a server by the client.  See section 17.1.3
4398   for the use of the Preference option by the client and the
4399   interpretation of Preference option data value.
4400
440122.9. Elapsed Time Option
4402
4403       0                   1                   2                   3
4404       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4405      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4406      |      OPTION_ELAPSED_TIME      |           option-len          |
4407      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4408      |          elapsed-time         |
4409      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4410
4411      option-code   OPTION_ELAPSED_TIME (8).
4412
4413      option-len    2.
4414
4415      elapsed-time  The amount of time since the client began its
4416                    current DHCP transaction.  This time is expressed in
4417                    hundredths of a second (10^-2 seconds).
4418
4419   A client MUST include an Elapsed Time option in messages to indicate
4420   how long the client has been trying to complete a DHCP message
4421   exchange.  The elapsed time is measured from the time at which the
4422   client sent the first message in the message exchange, and the
4423
4424
4425
4426Droms, et al.               Standards Track                    [Page 79]
4427
4428RFC 3315                     DHCP for IPv6                     July 2003
4429
4430
4431   elapsed-time field is set to 0 in the first message in the message
4432   exchange.  Servers and Relay Agents use the data value in this option
4433   as input to policy controlling how a server responds to a client
4434   message.  For example, the elapsed time option allows a secondary
4435   DHCP server to respond to a request when a primary server has not
4436   answered in a reasonable time.  The elapsed time value is an
4437   unsigned, 16 bit integer.  The client uses the value 0xffff to
4438   represent any elapsed time values greater than the largest time value
4439   that can be represented in the Elapsed Time option.
4440
444122.10. Relay Message Option
4442
4443   The Relay Message option carries a DHCP message in a Relay-forward or
4444   Relay-reply message.
4445
4446   The format of the Relay Message option is:
4447
4448       0                   1                   2                   3
4449       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4450      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4451      |        OPTION_RELAY_MSG       |           option-len          |
4452      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4453      |                                                               |
4454      .                       DHCP-relay-message                      .
4455      .                                                               .
4456      .                                                               .
4457      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4458
4459      option-code   OPTION_RELAY_MSG (9)
4460
4461      option-len    Length of DHCP-relay-message
4462
4463      DHCP-relay-message In a Relay-forward message, the received
4464                    message, relayed verbatim to the next relay agent
4465                    or server; in a Relay-reply message, the message to
4466                    be copied and relayed to the relay agent or client
4467                    whose address is in the peer-address field of the
4468                    Relay-reply message
4469
4470
4471
4472
4473
4474
4475
4476
4477
4478
4479
4480
4481
4482Droms, et al.               Standards Track                    [Page 80]
4483
4484RFC 3315                     DHCP for IPv6                     July 2003
4485
4486
448722.11. Authentication Option
4488
4489   The Authentication option carries authentication information to
4490   authenticate the identity and contents of DHCP messages.  The use of
4491   the Authentication option is described in section 21.  The format of
4492   the Authentication option is:
4493
4494     0                   1                   2                   3
4495     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4496    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4497    |          OPTION_AUTH          |          option-len           |
4498    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4499    |   protocol    |   algorithm   |      RDM      |               |
4500    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               |
4501    |                                                               |
4502    |          replay detection (64 bits)           +-+-+-+-+-+-+-+-+
4503    |                                               |   auth-info   |
4504    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               |
4505    .                   authentication information                  .
4506    .                       (variable length)                       .
4507    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4508
4509      option-code                  OPTION_AUTH (11)
4510
4511      option-len                   11 + length of authentication
4512                                   information field
4513
4514      protocol                     The authentication protocol used in
4515                                   this authentication option
4516
4517      algorithm                    The algorithm used in the
4518                                   authentication protocol
4519
4520      RDM                          The replay detection method used in
4521                                   this authentication option
4522
4523      Replay detection             The replay detection information for
4524                                   the RDM
4525
4526      authentication information   The authentication information,
4527                                   as specified by the protocol and
4528                                   algorithm used in this authentication
4529                                   option
4530
4531
4532
4533
4534
4535
4536
4537
4538Droms, et al.               Standards Track                    [Page 81]
4539
4540RFC 3315                     DHCP for IPv6                     July 2003
4541
4542
454322.12. Server Unicast Option
4544
4545   The server sends this option to a client to indicate to the client
4546   that it is allowed to unicast messages to the server.  The format of
4547   the Server Unicast option is:
4548
4549     0                   1                   2                   3
4550     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4551    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4552    |          OPTION_UNICAST       |        option-len             |
4553    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4554    |                                                               |
4555    |                       server-address                          |
4556    |                                                               |
4557    |                                                               |
4558    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4559
4560      option-code     OPTION_UNICAST (12).
4561
4562      option-len      16.
4563
4564      server-address  The IP address to which the client should send
4565                      messages delivered using unicast.
4566
4567   The server specifies the IPv6 address to which the client is to send
4568   unicast messages in the server-address field.  When a client receives
4569   this option, where permissible and appropriate, the client sends
4570   messages directly to the server using the IPv6 address specified in
4571   the server-address field of the option.
4572
4573   When the server sends a Unicast option to the client, some messages
4574   from the client will not be relayed by Relay Agents, and will not
4575   include Relay Agent options from the Relay Agents.  Therefore, a
4576   server should only send a Unicast option to a client when Relay
4577   Agents are not sending Relay Agent options.  A DHCP server rejects
4578   any messages sent inappropriately using unicast to ensure that
4579   messages are relayed by Relay Agents when Relay Agent options are in
4580   use.
4581
4582   Details about when the client may send messages to the server using
4583   unicast are in section 18.
4584
458522.13. Status Code Option
4586
4587   This option returns a status indication related to the DHCP message
4588   or option in which it appears.  The format of the Status Code option
4589   is:
4590
4591
4592
4593
4594Droms, et al.               Standards Track                    [Page 82]
4595
4596RFC 3315                     DHCP for IPv6                     July 2003
4597
4598
4599     0                   1                   2                   3
4600     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4601    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4602    |       OPTION_STATUS_CODE      |         option-len            |
4603    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4604    |          status-code          |                               |
4605    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
4606    .                                                               .
4607    .                        status-message                         .
4608    .                                                               .
4609    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4610
4611      option-code          OPTION_STATUS_CODE (13).
4612
4613      option-len           2 + length of status-message.
4614
4615      status-code          The numeric code for the status encoded in
4616                           this option.  The status codes are defined in
4617                           section 24.4.
4618
4619      status-message       A UTF-8 encoded text string suitable for
4620                           display to an end user, which MUST NOT be
4621                           null-terminated.
4622
4623   A Status Code option may appear in the options field of a DHCP
4624   message and/or in the options field of another option.  If the Status
4625   Code option does not appear in a message in which the option could
4626   appear, the status of the message is assumed to be Success.
4627
462822.14. Rapid Commit Option
4629
4630   The Rapid Commit option is used to signal the use of the two message
4631   exchange for address assignment.  The format of the Rapid Commit
4632   option is:
4633
4634     0                   1                   2                   3
4635     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4636    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4637    |      OPTION_RAPID_COMMIT      |               0               |
4638    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4639
4640      option-code     OPTION_RAPID_COMMIT (14).
4641
4642      option-len      0.
4643
4644   A client MAY include this option in a Solicit message if the client
4645   is prepared to perform the Solicit-Reply message exchange described
4646   in section 17.1.1.
4647
4648
4649
4650Droms, et al.               Standards Track                    [Page 83]
4651
4652RFC 3315                     DHCP for IPv6                     July 2003
4653
4654
4655   A server MUST include this option in a Reply message sent in response
4656   to a Solicit message when completing the Solicit-Reply message
4657   exchange.
4658
4659   DISCUSSION:
4660
4661      Each server that responds with a Reply to a Solicit that includes
4662      a Rapid Commit option will commit the assigned addresses in the
4663      Reply message to the client, and will not receive any confirmation
4664      that the client has received the Reply message.  Therefore, if
4665      more than one server responds to a Solicit that includes a Rapid
4666      Commit option, some servers will commit addresses that are not
4667      actually used by the client.
4668
4669      The problem of unused addresses can be minimized, for example, by
4670      designing the DHCP service so that only one server responds to the
4671      Solicit or by using relatively short lifetimes for assigned
4672      addresses.
4673
467422.15. User Class Option
4675
4676   The User Class option is used by a client to identify the type or
4677   category of user or applications it represents.
4678
4679   The format of the User Class option is:
4680
4681       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4682      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4683      |       OPTION_USER_CLASS       |          option-len           |
4684      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4685      .                                                               .
4686      .                          user-class-data                      .
4687      .                                                               .
4688      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4689
4690      option-code          OPTION_USER_CLASS (15).
4691
4692      option-len           Length of user class data field.
4693
4694      user-class-data      The user classes carried by the client.
4695
4696   The information contained in the data area of this option is
4697   contained in one or more opaque fields that represent the user class
4698   or classes of which the client is a member.  A server selects
4699   configuration information for the client based on the classes
4700   identified in this option.  For example, the User Class option can be
4701   used to configure all clients of people in the accounting department
4702
4703
4704
4705
4706Droms, et al.               Standards Track                    [Page 84]
4707
4708RFC 3315                     DHCP for IPv6                     July 2003
4709
4710
4711   with a different printer than clients of people in the marketing
4712   department.  The user class information carried in this option MUST
4713   be configurable on the client.
4714
4715   The data area of the user class option MUST contain one or more
4716   instances of user class data.  Each instance of the user class data
4717   is formatted as follows:
4718
4719      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
4720      |        user-class-len         |          opaque-data          |
4721      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
4722
4723   The user-class-len is two octets long and specifies the length of the
4724   opaque user class data in network byte order.
4725
4726   A server interprets the classes identified in this option according
4727   to its configuration to select the appropriate configuration
4728   information for the client.  A server may use only those user classes
4729   that it is configured to interpret in selecting configuration
4730   information for a client and ignore any other user classes.  In
4731   response to a message containing a User Class option, a server
4732   includes a User Class option containing those classes that were
4733   successfully interpreted by the server, so that the client can be
4734   informed of the classes interpreted by the server.
4735
473622.16. Vendor Class Option
4737
4738   This option is used by a client to identify the vendor that
4739   manufactured the hardware on which the client is running.  The
4740   information contained in the data area of this option is contained in
4741   one or more opaque fields that identify details of the hardware
4742   configuration.  The format of the Vendor Class option is:
4743
4744       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4745      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4746      |      OPTION_VENDOR_CLASS      |           option-len          |
4747      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4748      |                       enterprise-number                       |
4749      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4750      .                                                               .
4751      .                       vendor-class-data                       .
4752      .                             . . .                             .
4753      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4754
4755      option-code          OPTION_VENDOR_CLASS (16).
4756
4757      option-len           4 + length of vendor class data field.
4758
4759
4760
4761
4762Droms, et al.               Standards Track                    [Page 85]
4763
4764RFC 3315                     DHCP for IPv6                     July 2003
4765
4766
4767      enterprise-number    The vendor's registered Enterprise Number as
4768                           registered with IANA [6].
4769
4770      vendor-class-data    The hardware configuration of the host on
4771                           which the client is running.
4772
4773   The vendor-class-data is composed of a series of separate items, each
4774   of which describes some characteristic of the client's hardware
4775   configuration.  Examples of vendor-class-data instances might include
4776   the version of the operating system the client is running or the
4777   amount of memory installed on the client.
4778
4779   Each instance of the vendor-class-data is formatted as follows:
4780
4781      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
4782      |       vendor-class-len        |          opaque-data          |
4783      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
4784
4785   The vendor-class-len is two octets long and specifies the length of
4786   the opaque vendor class data in network byte order.
4787
478822.17. Vendor-specific Information Option
4789
4790   This option is used by clients and servers to exchange
4791   vendor-specific information.
4792
4793   The format of the Vendor-specific Information option is:
4794
4795       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4796      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4797      |      OPTION_VENDOR_OPTS       |           option-len          |
4798      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4799      |                       enterprise-number                       |
4800      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4801      .                                                               .
4802      .                          option-data                          .
4803      .                                                               .
4804      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4805
4806      option-code          OPTION_VENDOR_OPTS (17)
4807
4808      option-len           4 + length of option-data field
4809
4810      enterprise-number    The vendor's registered Enterprise Number as
4811                           registered with IANA [6].
4812
4813
4814
4815
4816
4817
4818Droms, et al.               Standards Track                    [Page 86]
4819
4820RFC 3315                     DHCP for IPv6                     July 2003
4821
4822
4823      option-data          An opaque object of option-len octets,
4824                           interpreted by vendor-specific code on the
4825                           clients and servers
4826
4827   The definition of the information carried in this option is vendor
4828   specific.  The vendor is indicated in the enterprise-number field.
4829   Use of vendor-specific information allows enhanced operation,
4830   utilizing additional features in a vendor's DHCP implementation.  A
4831   DHCP client that does not receive requested vendor-specific
4832   information will still configure the host device's IPv6 stack to be
4833   functional.
4834
4835   The encapsulated vendor-specific options field MUST be encoded as a
4836   sequence of code/length/value fields of identical format to the DHCP
4837   options field.  The option codes are defined by the vendor identified
4838   in the enterprise-number field and are not managed by IANA.  Each of
4839   the encapsulated options is formatted as follows:
4840
4841       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4842      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4843      |          opt-code             |             option-len        |
4844      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4845      .                                                               .
4846      .                          option-data                          .
4847      .                                                               .
4848      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4849
4850      opt-code             The code for the encapsulated option.
4851
4852      option-len           An unsigned integer giving the length of the
4853                           option-data field in this encapsulated option
4854                           in octets.
4855
4856      option-data          The data area for the encapsulated option.
4857
4858   Multiple instances of the Vendor-specific Information option may
4859   appear in a DHCP message.  Each instance of the option is interpreted
4860   according to the option codes defined by the vendor identified by the
4861   Enterprise Number in that option.
4862
486322.18. Interface-Id Option
4864
4865   The relay agent MAY send the Interface-id option to identify the
4866   interface on which the client message was received.  If a relay agent
4867   receives a Relay-reply message with an Interface-id option, the relay
4868   agent relays the message to the client through the interface
4869   identified by the option.
4870
4871
4872
4873
4874Droms, et al.               Standards Track                    [Page 87]
4875
4876RFC 3315                     DHCP for IPv6                     July 2003
4877
4878
4879   The format of the Interface ID option is:
4880
4881     0                   1                   2                   3
4882     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4883    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4884    |      OPTION_INTERFACE_ID      |         option-len            |
4885    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4886    .                                                               .
4887    .                         interface-id                          .
4888    .                                                               .
4889    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4890
4891      option-code          OPTION_INTERFACE_ID (18).
4892
4893      option-len           Length of interface-id field.
4894
4895      interface-id         An opaque value of arbitrary length generated
4896                           by the relay agent to identify one of the
4897                           relay agent's interfaces.
4898
4899   The server MUST copy the Interface-Id option from the Relay-Forward
4900   message into the Relay-Reply message the server sends to the relay
4901   agent in response to the Relay-Forward message.  This option MUST NOT
4902   appear in any message except a Relay-Forward or Relay-Reply message.
4903
4904   Servers MAY use the Interface-ID for parameter assignment policies.
4905   The Interface-ID SHOULD be considered an opaque value, with policies
4906   based on exact match only; that is, the Interface-ID SHOULD NOT be
4907   internally parsed by the server.  The Interface-ID value for an
4908   interface SHOULD be stable and remain unchanged, for example, after
4909   the relay agent is restarted; if the Interface-ID changes, a server
4910   will not be able to use it reliably in parameter assignment policies.
4911
491222.19. Reconfigure Message Option
4913
4914   A server includes a Reconfigure Message option in a Reconfigure
4915   message to indicate to the client whether the client responds with a
4916   Renew message or an Information-request message.  The format of this
4917   option is:
4918
4919     0                   1                   2                   3
4920     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4921    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4922    |      OPTION_RECONF_MSG        |         option-len            |
4923    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4924    |    msg-type   |
4925    +-+-+-+-+-+-+-+-+
4926
4927
4928
4929
4930Droms, et al.               Standards Track                    [Page 88]
4931
4932RFC 3315                     DHCP for IPv6                     July 2003
4933
4934
4935      option-code          OPTION_RECONF_MSG (19).
4936
4937      option-len           1.
4938
4939      msg-type             5 for Renew message, 11 for
4940                           Information-request message.
4941
4942   The Reconfigure Message option can only appear in a Reconfigure
4943   message.
4944
494522.20. Reconfigure Accept Option
4946
4947   A client uses the Reconfigure Accept option to announce to the server
4948   whether the client is willing to accept Reconfigure messages, and a
4949   server uses this option to tell the client whether or not to accept
4950   Reconfigure messages.  The default behavior, in the absence of this
4951   option, means unwillingness to accept Reconfigure messages, or
4952   instruction not to accept Reconfigure messages, for the client and
4953   server messages, respectively.  The following figure gives the format
4954   of the Reconfigure Accept option:
4955
4956     0                   1                   2                   3
4957     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
4958    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4959    |     OPTION_RECONF_ACCEPT      |               0               |
4960    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4961
4962      option-code   OPTION_RECONF_ACCEPT (20).
4963
4964      option-len    0.
4965
496623. Security Considerations
4967
4968   The threat to DHCP is inherently an insider threat (assuming a
4969   properly configured network where DHCPv6 ports are blocked on the
4970   perimeter gateways of the enterprise).  Regardless of the gateway
4971   configuration, however, the potential attacks by insiders and
4972   outsiders are the same.
4973
4974   Use of manually configured preshared keys for IPsec between relay
4975   agents and servers does not defend against replayed DHCP messages.
4976   Replayed messages can represent a DOS attack through exhaustion of
4977   processing resources, but not through mis-configuration or exhaustion
4978   of other resources such as assignable addresses.
4979
4980   One attack specific to a DHCP client is the establishment of a
4981   malicious server with the intent of providing incorrect configuration
4982   information to the client.  The motivation for doing so may be to
4983
4984
4985
4986Droms, et al.               Standards Track                    [Page 89]
4987
4988RFC 3315                     DHCP for IPv6                     July 2003
4989
4990
4991   mount a "man in the middle" attack that causes the client to
4992   communicate with a malicious server instead of a valid server for
4993   some service such as DNS or NTP.  The malicious server may also mount
4994   a denial of service attack through misconfiguration of the client
4995   that causes all network communication from the client to fail.
4996
4997   There is another threat to DHCP clients from mistakenly or
4998   accidentally configured DHCP servers that answer DHCP client requests
4999   with unintentionally incorrect configuration parameters.
5000
5001   A DHCP client may also be subject to attack through the receipt of a
5002   Reconfigure message from a malicious server that causes the client to
5003   obtain incorrect configuration information from that server.  Note
5004   that although a client sends its response (Renew or
5005   Information-request message) through a relay agent and, therefore,
5006   that response will only be received by servers to which DHCP messages
5007   are relayed, a malicious server could send a Reconfigure message to a
5008   client, followed (after an appropriate delay) by a Reply message that
5009   would be accepted by the client.  Thus, a malicious server that is
5010   not on the network path between the client and the server may still
5011   be able to mount a Reconfigure attack on a client.  The use of
5012   transaction IDs that are cryptographically sound and cannot easily be
5013   predicted will also reduce the probability that such an attack will
5014   be successful.
5015
5016   The threat specific to a DHCP server is an invalid client
5017   masquerading as a valid client.  The motivation for this may be for
5018   theft of service, or to circumvent auditing for any number of
5019   nefarious purposes.
5020
5021   The threat common to both the client and the server is the resource
5022   "denial of service" (DoS) attack.  These attacks typically involve
5023   the exhaustion of available addresses, or the exhaustion of CPU or
5024   network bandwidth, and are present anytime there is a shared
5025   resource.
5026
5027   In the case where relay agents add additional options to Relay
5028   Forward messages, the messages exchanged between relay agents and
5029   servers may be used to mount a "man in the middle" or denial of
5030   service attack.
5031
5032   This threat model does not consider the privacy of the contents of
5033   DHCP messages to be important.  DHCP is not used to exchange
5034   authentication or configuration information that must be kept secret
5035   from other networks nodes.
5036
5037
5038
5039
5040
5041
5042Droms, et al.               Standards Track                    [Page 90]
5043
5044RFC 3315                     DHCP for IPv6                     July 2003
5045
5046
5047   DHCP authentication provides for authentication of the identity of
5048   DHCP clients and servers, and for the integrity of messages delivered
5049   between DHCP clients and servers.  DHCP authentication does not
5050   provide any privacy for the contents of DHCP messages.
5051
5052   The Delayed Authentication protocol described in section 21.4 uses a
5053   secret key that is shared between a client and a server.  The use of
5054   a "DHCP realm" in the shared key allows identification of
5055   administrative domains so that a client can select the appropriate
5056   key or keys when roaming between administrative domains.  However,
5057   the Delayed Authentication protocol does not define any mechanism for
5058   sharing of keys, so a client may require separate keys for each
5059   administrative domain it encounters.  The use of shared keys may not
5060   scale well and does not provide for repudiation of compromised keys.
5061   This protocol is focused on solving the intradomain problem where the
5062   out-of-band exchange of a shared key is feasible.
5063
5064   Because of the opportunity for attack through the Reconfigure
5065   message, a DHCP client MUST discard any Reconfigure message that does
5066   not include authentication or that does not pass the validation
5067   process for the authentication protocol.
5068
5069   The Reconfigure Key protocol described in section 21.5 provides
5070   protection against the use of a Reconfigure message by a malicious
5071   DHCP server to mount a denial of service or man-in-the-middle attack
5072   on a client.  This protocol can be compromised by an attacker that
5073   can intercept the initial message in which the DHCP server sends the
5074   key to the client.
5075
5076   Communication between a server and a relay agent, and communication
5077   between relay agents, can be secured through the use of IPSec, as
5078   described in section 21.1.  The use of manual configuration and
5079   installation of static keys are acceptable in this instance because
5080   relay agents and the server will belong to the same administrative
5081   domain and the relay agents will require other specific configuration
5082   (for example, configuration of the DHCP server address) as well as
5083   the IPSec configuration.
5084
508524. IANA Considerations
5086
5087   This document defines several new name spaces associated with DHCPv6
5088   and DHCPv6 options:
5089
5090      -  Message types
5091
5092      -  Status codes
5093
5094      -  DUID
5095
5096
5097
5098Droms, et al.               Standards Track                    [Page 91]
5099
5100RFC 3315                     DHCP for IPv6                     July 2003
5101
5102
5103      -  Option codes
5104
5105   IANA has established a registry of values for each of these name
5106   spaces, which are described in the remainder of this section.  These
5107   name spaces will be managed by the IANA and all will be managed
5108   separately from the name spaces defined for DHCPv4.
5109
5110   New multicast addresses, message types, status codes, and DUID types
5111   are assigned via Standards Action [11].
5112
5113   New DHCP option codes are tentatively assigned after the
5114   specification for the associated option, published as an Internet
5115   Draft, has received expert review by a designated expert [11].  The
5116   final assignment of DHCP option codes is through Standards Action, as
5117   defined in RFC 2434 [11].
5118
5119   This document also references three name spaces in section 21 that
5120   are associated with the Authentication Option (section 22.11).  These
5121   name spaces are defined by the authentication mechanism for DHCPv4 in
5122   RFC 3118 [4].
5123
5124   The authentication name spaces currently registered by IANA will
5125   apply to both DHCPv6 and DHCPv4.  In the future, specifications that
5126   define new Protocol, Algorithm and RDM mechanisms will explicitly
5127   define whether the new mechanisms are used with DHCPv4, DHCPv6 or
5128   both.
5129
513024.1. Multicast Addresses
5131
5132   Section 5.1 defines the following multicast addresses, which have
5133   been assigned by IANA for use by DHCPv6:
5134
5135      All_DHCP_Relay_Agents_and_Servers address:   FF02::1:2
5136
5137      All_DHCP_Servers address:                    FF05::1:3
5138
5139
5140
5141
5142
5143
5144
5145
5146
5147
5148
5149
5150
5151
5152
5153
5154Droms, et al.               Standards Track                    [Page 92]
5155
5156RFC 3315                     DHCP for IPv6                     July 2003
5157
5158
515924.2. DHCP Message Types
5160
5161   IANA has recorded the following message types (defined in section
5162   5.3).  IANA will maintain the registry of DHCP message types.
5163
5164      SOLICIT               1
5165
5166      ADVERTISE             2
5167
5168      REQUEST               3
5169
5170      CONFIRM               4
5171
5172      RENEW                 5
5173
5174      REBIND                6
5175
5176      REPLY                 7
5177
5178      RELEASE               8
5179
5180      DECLINE               9
5181
5182      RECONFIGURE           10
5183
5184      INFORMATION-REQUEST   11
5185
5186      RELAY-FORW            12
5187
5188      RELAY-REPL            13
5189
5190
5191
5192
5193
5194
5195
5196
5197
5198
5199
5200
5201
5202
5203
5204
5205
5206
5207
5208
5209
5210Droms, et al.               Standards Track                    [Page 93]
5211
5212RFC 3315                     DHCP for IPv6                     July 2003
5213
5214
521524.3. DHCP Options
5216
5217   IANA has recorded the following option-codes (as defined in section
5218   22).  IANA will maintain the registry of DHCP option codes.
5219
5220      OPTION_CLIENTID       1
5221
5222      OPTION_SERVERID       2
5223
5224      OPTION_IA_NA          3
5225
5226      OPTION_IA_TA          4
5227
5228      OPTION_IAADDR         5
5229
5230      OPTION_ORO            6
5231
5232      OPTION_PREFERENCE     7
5233
5234      OPTION_ELAPSED_TIME   8
5235
5236      OPTION_RELAY_MSG      9
5237
5238      OPTION_AUTH           11
5239
5240      OPTION_UNICAST        12
5241
5242      OPTION_STATUS_CODE    13
5243
5244      OPTION_RAPID_COMMIT   14
5245
5246      OPTION_USER_CLASS     15
5247
5248      OPTION_VENDOR_CLASS   16
5249
5250      OPTION_VENDOR_OPTS    17
5251
5252      OPTION_INTERFACE_ID   18
5253
5254      OPTION_RECONF_MSG     19
5255
5256      OPTION_RECONF_ACCEPT  20
5257
5258
5259
5260
5261
5262
5263
5264
5265
5266Droms, et al.               Standards Track                    [Page 94]
5267
5268RFC 3315                     DHCP for IPv6                     July 2003
5269
5270
527124.4. Status Codes
5272
5273   IANA has recorded the status codes defined in the following table.
5274   IANA will manage the definition of additional status codes in the
5275   future.
5276
5277   Name         Code Description
5278   ----------   ---- -----------
5279   Success         0 Success.
5280   UnspecFail      1 Failure, reason unspecified; this
5281                     status code is sent by either a client
5282                     or a server to indicate a failure
5283                     not explicitly specified in this
5284                     document.
5285   NoAddrsAvail    2 Server has no addresses available to assign to
5286                     the IA(s).
5287   NoBinding       3 Client record (binding) unavailable.
5288   NotOnLink       4 The prefix for the address is not appropriate for
5289                     the link to which the client is attached.
5290   UseMulticast    5 Sent by a server to a client to force the
5291                     client to send messages to the server.
5292                     using the All_DHCP_Relay_Agents_and_Servers
5293                     address.
5294
529524.5. DUID
5296
5297   IANA has recorded the following DUID types (as defined in section
5298   9.1).  IANA will manage the definition of additional DUID types in
5299   the future.
5300
5301      DUID-LLT                       1
5302
5303      DUID-EN                        2
5304
5305      DUID-LL                        3
5306
530725. Acknowledgments
5308
5309   Thanks to the DHC Working Group and the members of the IETF for their
5310   time and input into the specification.  In particular, thanks also
5311   for the consistent input, ideas, and review by (in alphabetical
5312   order) Bernard Aboba, Bill Arbaugh, Thirumalesh Bhat, Steve Bellovin,
5313   A. K. Vijayabhaskar, Brian Carpenter, Matt Crawford, Francis Dupont,
5314   Richard Hussong, Kim Kinnear, Fredrik Lindholm, Tony Lindstrom, Josh
5315   Littlefield, Gerald Maguire, Jack McCann, Shin Miyakawa, Thomas
5316   Narten, Erik Nordmark, Jarno Rajahalme, Yakov Rekhter, Mark Stapp,
5317   Matt Thomas, Sue Thomson, Tatuya Jinmei and Phil Wells.
5318
5319
5320
5321
5322Droms, et al.               Standards Track                    [Page 95]
5323
5324RFC 3315                     DHCP for IPv6                     July 2003
5325
5326
5327   Thanks to Steve Deering and Bob Hinden, who have consistently taken
5328   the time to discuss the more complex parts of the IPv6
5329   specifications.
5330
5331   And, thanks to Steve Deering for pointing out at IETF 51 in London
5332   that the DHCPv6 specification has the highest revision number of any
5333   Internet Draft.
5334
533526. References
5336
533726.1. Normative References
5338
5339   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
5340        Levels", BCP 14, RFC 2119, March 1997.
5341
5342   [2]  Crawford, M., "Transmission of IPv6 Packets over Ethernet
5343        Networks", RFC 2464, December 1998.
5344
5345   [3]  Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
5346        Specification", RFC 2460, December 1998.
5347
5348   [4]  Droms, R., Ed. and W. Arbaugh, Ed., "Authentication for DHCP
5349        Messages", RFC 3118, June 2001.
5350
5351   [5]  Hinden, R. and S. Deering, "IP Version 6 Addressing
5352        Architecture", RFC 2373, July 1998.
5353
5354   [6]  IANA.  Private Enterprise Numbers.
5355        http://www.iana.org/assignments/enterprise-numbers.html.
5356
5357   [7]  Kent, S. and R. Atkinson, "Security Architecture for the
5358        Internet Protocol", RFC 2401, November 1998.
5359
5360   [8]  Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed-Hashing
5361        for Message Authentication", RFC 2104, February 1997.
5362
5363   [9]  Mills, D., "Network Time Protocol (Version 3) Specification,
5364        Implementation", RFC 1305, March 1992.
5365
5366   [10] Mockapetris, P., "Domain names - implementation and
5367        specification", RFC 1035, November 1987.
5368
5369   [11] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
5370        Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
5371
5372   [12] Narten, T. and R. Draves, "Privacy Extensions for Stateless
5373        Address Autoconfiguration in IPv6", RFC 3041, January 2001.
5374
5375
5376
5377
5378Droms, et al.               Standards Track                    [Page 96]
5379
5380RFC 3315                     DHCP for IPv6                     July 2003
5381
5382
5383   [13] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery for
5384        IP Version 6 (IPv6)", RFC 2461, December 1998.
5385
5386   [14] Plummer, D.C., "Ethernet Address Resolution Protocol:  Or
5387        converting network protocol addresses to 48.bit Ethernet address
5388        for transmission on Ethernet hardware", STD 37, RFC 826,
5389        November 1982.
5390
5391   [15] Postel, J., "User Datagram Protocol", STD 6, RFC 768, August
5392        1980.
5393
5394   [16] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, April
5395        1992.
5396
5397   [17] Thomson, S. and T. Narten, "IPv6 Stateless Address
5398        Autoconfiguration", RFC 2462, December 1998.
5399
540026.2. Informative References
5401
5402   [18] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
5403        Extensions", RFC 2132, March 1997.
5404
5405   [19] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
5406        March 1997.
5407
5408   [20] R. Droms, Ed.  DNS Configuration options for DHCPv6.  April
5409        2002.  Work in Progress.
5410
5411   [21] A. K. Vijayabhaskar.  Time Configuration Options for DHCPv6.
5412        May 2002.  Work in Progress.
5413
5414   [22] Vixie, P., Ed., Thomson, S., Rekhter, Y. and J. Bound, "Dynamic
5415        Updates in the Domain Name System (DNS UPDATE)", RFC 2136, April
5416        1997.
5417
5418
5419
5420
5421
5422
5423
5424
5425
5426
5427
5428
5429
5430
5431
5432
5433
5434Droms, et al.               Standards Track                    [Page 97]
5435
5436RFC 3315                     DHCP for IPv6                     July 2003
5437
5438
5439A. Appearance of Options in Message Types
5440
5441   The following table indicates with a "*" the options are allowed in
5442   each DHCP message type:
5443
5444           Client Server IA_NA  Option Pref  Time Relay Auth. Server
5445             ID     ID   IA_TA  Request            Msg.       Unica.
5446   Solicit   *             *      *           *           *
5447   Advert.   *      *      *            *                 *
5448   Request   *      *      *      *           *           *
5449   Confirm   *             *      *           *           *
5450   Renew     *      *      *      *           *           *
5451   Rebind    *             *      *           *           *
5452   Decline   *      *      *      *           *           *
5453   Release   *      *      *      *           *           *
5454   Reply     *      *      *            *                 *     *
5455   Reconf.   *      *             *                       *
5456   Inform.   * (see note)         *           *           *
5457   R-forw.                                          *     *
5458   R-repl.                                          *     *
5459
5460   NOTE:
5461
5462      Only included in Information-Request messages that are sent
5463      in response to a Reconfigure (see section 19.4.3).
5464
5465            Status  Rap. User  Vendor Vendor Inter. Recon. Recon.
5466             Code  Comm. Class Class  Spec.    ID    Msg.  Accept
5467   Solicit           *     *     *      *                    *
5468   Advert.    *            *     *      *                    *
5469   Request                 *     *      *                    *
5470   Confirm                 *     *      *
5471   Renew                   *     *      *                    *
5472   Rebind                  *     *      *                    *
5473   Decline                 *     *      *
5474   Release                 *     *      *
5475   Reply      *      *     *     *      *                    *
5476   Reconf.                                            *
5477   Inform.                 *     *      *                    *
5478   R-forw.                 *     *      *      *
5479   R-repl.                 *     *      *      *
5480
5481
5482
5483
5484
5485
5486
5487
5488
5489
5490Droms, et al.               Standards Track                    [Page 98]
5491
5492RFC 3315                     DHCP for IPv6                     July 2003
5493
5494
5495B. Appearance of Options in the Options Field of DHCP Options
5496
5497   The following table indicates with a "*" where options can appear in
5498   the options field of other options:
5499
5500                Option  IA_NA/ IAADDR Relay  Relay
5501                Field   IA_TA         Forw.  Reply
5502   Client ID      *
5503   Server ID      *
5504   IA_NA/IA_TA    *
5505   IAADDR                 *
5506   ORO            *
5507   Preference     *
5508   Elapsed Time   *
5509   Relay Message                        *      *
5510   Authentic.     *
5511   Server Uni.    *
5512   Status Code    *       *       *
5513   Rapid Comm.    *
5514   User Class     *
5515   Vendor Class   *
5516   Vendor Info.   *
5517   Interf. ID                           *      *
5518   Reconf. MSG.   *
5519   Reconf. Accept *
5520
5521   Note: "Relay Forw" / "Relay Reply" options appear in the options
5522   field of the message but may only appear in these messages.
5523
5524Chair's Address
5525
5526   The working group can be contacted via the current chair:
5527
5528   Ralph Droms
5529   Cisco Systems
5530   1414 Massachusetts Avenue
5531   Boxborough, MA 01719
5532
5533   Phone: (978) 936-1674
5534   EMail: rdroms@cisco.com
5535
5536
5537
5538
5539
5540
5541
5542
5543
5544
5545
5546Droms, et al.               Standards Track                    [Page 99]
5547
5548RFC 3315                     DHCP for IPv6                     July 2003
5549
5550
5551Authors' Addresses
5552
5553   Jim Bound
5554   Hewlett Packard Corporation
5555   ZK3-3/W20
5556   110 Spit Brook Road
5557   Nashua, NH 03062-2698
5558   USA
5559
5560   Phone:  +1 603 884 0062
5561   EMail:  Jim.Bound@hp.com
5562
5563   Bernie Volz
5564   116 Hawkins Pond Road
5565   Center Harbor, NH  03226-3103
5566   USA
5567
5568   Phone:  +1-508-259-3734
5569   EMail:  volz@metrocast.net
5570
5571   Ted Lemon
5572   Nominum, Inc.
5573   950 Charter Street
5574   Redwood City, CA 94043
5575   USA
5576
5577   EMail:  Ted.Lemon@nominum.com
5578
5579   Charles E. Perkins
5580   Communications Systems Lab
5581   Nokia Research Center
5582   313 Fairchild Drive
5583   Mountain View, California 94043
5584   USA
5585
5586   Phone:  +1-650 625-2986
5587   EMail:  charles.perkins@nokia.com
5588
5589   Mike Carney
5590   Sun Microsystems, Inc
5591   17 Network Circle
5592   Menlo Park, CA 94025
5593   USA
5594
5595   Phone:  +1-650-786-4171
5596   EMail:  michael.carney@sun.com
5597
5598
5599
5600
5601
5602Droms, et al.               Standards Track                   [Page 100]
5603
5604RFC 3315                     DHCP for IPv6                     July 2003
5605
5606
5607Full Copyright Statement
5608
5609   Copyright (C) The Internet Society (2003).  All Rights Reserved.
5610
5611   This document and translations of it may be copied and furnished to
5612   others, and derivative works that comment on or otherwise explain it
5613   or assist in its implementation may be prepared, copied, published
5614   and distributed, in whole or in part, without restriction of any
5615   kind, provided that the above copyright notice and this paragraph are
5616   included on all such copies and derivative works.  However, this
5617   document itself may not be modified in any way, such as by removing
5618   the copyright notice or references to the Internet Society or other
5619   Internet organizations, except as needed for the purpose of
5620   developing Internet standards in which case the procedures for
5621   copyrights defined in the Internet Standards process must be
5622   followed, or as required to translate it into languages other than
5623   English.
5624
5625   The limited permissions granted above are perpetual and will not be
5626   revoked by the Internet Society or its successors or assigns.
5627
5628   This document and the information contained herein is provided on an
5629   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
5630   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
5631   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
5632   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
5633   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
5634
5635Acknowledgement
5636
5637   Funding for the RFC Editor function is currently provided by the
5638   Internet Society.
5639
5640
5641
5642
5643
5644
5645
5646
5647
5648
5649
5650
5651
5652
5653
5654
5655
5656
5657
5658Droms, et al.               Standards Track                   [Page 101]
5659
5660