Gerrit Renker 22338f09bd dccp tfrc: Increase number of RTT samples ... This improves the receiver RTT sampling algorithm so that it tries harder to get as many RTT samples as possible. The algorithm is based the concepts presented in RFC 4340, 8.1, using timestamps and the CCVal window counter. There exist 4 cases for the CCVal difference: * == 0: less than RTT/4 passed since last packet -- unusable; * > 4: (much) more than 1 RTT has passed since last packet -- also unusable; * == 4: perfect sample (exactly one RTT has passed since last packet); * 1..3: sub-optimal sample (between RTT/4 and 3*RTT/4 has passed). In the last case the algorithm tried to optimise by storing away the candidate and then re-trying next time. The problem is that * a large number of samples is needed to smooth out the inaccuracies of the algorithm; * the sender may not be sending enough packets to warrant a "next time"; * hence it is better to use suboptimal samples whenever possible. The algorithm now stores away the current sample only if the difference is 0. Applicability and background ---------------------------- A realistic example is MP3 streaming where packets are sent at a rate of less than one packet per RTT, which means that suitable samples are absent for a very long time. The effectiveness of using suboptimal samples (with a delta between 1 and 4) was confirmed by instrumenting the algorithm with counters. The results of two 20 second test runs were: * With the old algorithm and a total of 38442 function calls, only 394 of these calls resulted in usable RTT samples (about 1%), and 378 out of these were "perfect" samples and 28013 (unused) samples had a delta of 1..3. * With the new algorithm and a total of 37057 function calls, 1702 usable RTT samples were retrieved (about 4.6%), 5 out of these were "perfect" samples. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>		2008-09-04 07:45:42 +02:00
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ccids	dccp tfrc: Increase number of RTT samples	2008-09-04 07:45:42 +02:00
ackvec.c	dccp ccid-2: Separate option parsing from CCID processing	2008-09-04 07:45:37 +02:00
ackvec.h	dccp ccid-2: Separate option parsing from CCID processing	2008-09-04 07:45:37 +02:00
ccid.c	dccp: Auto-load (when supported) CCID plugins for negotiation	2008-09-04 07:45:31 +02:00
ccid.h	dccp: Return-value convention of hc_tx_send_packet()	2008-09-04 07:45:38 +02:00
dccp.h	dccp: Clamping RTT values	2008-09-04 07:45:41 +02:00
diag.c	dccp ccid-2: Phase out the use of boolean Ack Vector sysctl	2008-09-04 07:45:31 +02:00
feat.c	dccp ccid-2: Use feature-negotiation to report Ack Ratio changes	2008-09-04 07:45:32 +02:00
feat.h	dccp: Debugging functions for feature negotiation	2008-09-04 07:45:32 +02:00
input.c	dccp: Clamping RTT values	2008-09-04 07:45:41 +02:00
ipv4.c	dccp: Cleanup routines for feature negotiation	2008-09-04 07:45:26 +02:00
ipv6.c	dccp: Cleanup routines for feature negotiation	2008-09-04 07:45:26 +02:00
ipv6.h
Kconfig	dccp ccid-2: Remove old infrastructure	2008-09-04 07:45:37 +02:00
Makefile	dccp: Policy-based packet dequeueing infrastructure	2008-09-04 07:45:39 +02:00
minisocks.c	dccp: Fix the adjustments to AWL and SWL	2008-09-04 07:45:35 +02:00
options.c	dccp ccid-2: Separate option parsing from CCID processing	2008-09-04 07:45:37 +02:00
output.c	dccp: Policy-based packet dequeueing infrastructure	2008-09-04 07:45:39 +02:00
probe.c	dccp: Reduce noise in output and convert to ktime_t	2008-09-04 07:45:36 +02:00
proto.c	dccp tfrc: Let dccp_tfrc_lib do the sampling work	2008-09-04 07:45:41 +02:00
qpolicy.c	dccp qpolicy: Parameter checking of cmsg qpolicy parameters	2008-09-04 07:45:40 +02:00
sysctl.c	dccp: Initialisation and type-checking of feature sysctls	2008-09-04 07:45:32 +02:00
timer.c	dccp ccid-3: Runtime verification of timer resolution	2008-09-04 07:45:40 +02:00