netinet/cc/cc_htcp.c

83 /* RTT_ref (ms) used in the calculation of alpha if RTT scaling is enabled. */
91  * value of alpha, based on the function defined in the HTCP spec.
105  * The "16" value is the "1" term in the alpha function shifted up by
108  * The "160" value is the "10" multiplier in the alpha function multiplied by
117  * different tick timers, which we have to adjust for in the alpha calculation
151 	int		alpha;
165  * htcp_recalc_alpha() before alpha will stop increasing due to overflow.
211 		 * or a congestion event (when alpha equals 1).
213 		if (htcp_data->alpha == 1 ||
218 				/* Increment cwnd by alpha segments. */
219 				CCV(ccv, snd_cwnd) += htcp_data->alpha *
224 				 * Increment cwnd by alpha/cwnd segments to
225 				 * approximate an increase of alpha segments
228 				CCV(ccv, snd_cwnd) += (((htcp_data->alpha <<
255 	htcp_data->alpha = HTCP_INIT_ALPHA;
376 	int alpha, diff, now;
384 	 * the wrap point, our alpha calcs will be completely wrong. We cut our
385 	 * losses and restart alpha from scratch by setting t_last_cong = now -
389 	 * is growing by until alpha regains the value it held prior to taking
397 	/* Cap alpha if the value of diff would overflow HTCP_CALC_ALPHA(). */
401 		 * increase alpha according to the function defined in the spec.
404 			alpha = HTCP_CALC_ALPHA(diff);
411 				alpha = max(1, (2 * ((1 << HTCP_SHIFT) -
412 				    htcp_data->beta) * alpha) >> HTCP_SHIFT);
415 			 * RTT scaling: (RTT / RTT_ref) * alpha
416 			 * alpha will be the raw value from HTCP_CALC_ALPHA() if
421 				alpha = max(1, (min(max(HTCP_MINROWE,
423 				    htcp_rtt_ref), HTCP_MAXROWE) * alpha)
427 			alpha = 1;
429 		htcp_data->alpha = alpha;