linux/net/dccp
Gerrit Renker a3cbdde8e9 dccp ccid-3: Preventing Oscillations
This implements [RFC 3448, 4.5], which performs congestion avoidance behaviour
by reducing the transmit rate as the queueing delay (measured in terms of
long-term RTT) increases.

Oscillation can be turned on/off via a module option (do_osc_prev) and via sysfs
(using mode 0644), the default is off.

Overflow analysis:
------------------
 * oscillation prevention is done after update_x(), so that t_ipi <= 64000;
 * hence the multiplication "t_ipi * sqrt(R_sample)" needs 64 bits;
 * done using u64 for sqrt_sample and explicit typecast of t_ipi;
 * the divisor, R_sqmean, is non-zero because oscillation prevention is first
   called when receiving the second feedback packet, and tfrc_scaled_rtt() > 0.

A detailed discussion of the algorithm (with plots) is on
http://www.erg.abdn.ac.uk/users/gerrit/dccp/notes/ccid3/sender_notes/oscillation_prevention/

The algorithm has negative side effects:
  * when allowing to decrease t_ipi (leads to a large RTT) and
  * when using it during slow-start;
both uses are therefore disabled.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
2008-09-04 07:45:43 +02:00
..
ccids dccp ccid-3: Preventing Oscillations 2008-09-04 07:45:43 +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 Remove obsolete #include <linux/config.h> 2006-06-30 19:25:36 +02:00
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