linux/net/dccp/ccids
Gerrit Renker 113ced1f52 dccp ccid-2: Perform congestion-window validation
CCID-2's cwnd increases like TCP during slow-start, which has implications for
 * the local Sequence Window value (should be > cwnd),
 * the Ack Ratio value.
Hence an exponential growth, if it does not reflect the actual network
conditions, can quickly lead to instability.

This patch adds congestion-window validation (RFC2861) to CCID-2:
 * cwnd is constrained if the sender is application limited;
 * cwnd is reduced after a long idle period, as suggested in the '90 paper
   by Van Jacobson, in RFC 2581 (sec. 4.1);
 * cwnd is never reduced below the RFC 3390 initial window.

As marked in the comments, the code is actually almost a direct copy of the
TCP congestion-window-validation algorithms. By continuing this work, it may
in future be possible to use the TCP code (not possible at the moment).

The mechanism can be turned off using a module parameter. Sampling of the
currently-used window (moving-maximum) is however done constantly; this is
used to determine the expected window, which can be exploited to regulate
DCCP's Sequence Window value.

This patch also sets slow-start-after-idle (RFC 4341, 5.1), i.e. it behaves like
TCP when net.ipv4.tcp_slow_start_after_idle = 1.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
2011-07-04 12:37:49 -06:00
..
lib net: return operator cleanup 2010-09-23 14:33:39 -07:00
ccid2.c dccp ccid-2: Perform congestion-window validation 2011-07-04 12:37:49 -06:00
ccid2.h dccp ccid-2: Perform congestion-window validation 2011-07-04 12:37:49 -06:00
ccid3.c dccp: Return-value convention of hc_tx_send_packet() 2010-10-28 10:27:00 -07:00
ccid3.h dccp ccid-3: Remove redundant 'options_received' struct 2010-09-21 12:14:26 +02:00
Kconfig dccp ccid-3: use per-route RTO or TCP RTO as fallback 2010-08-30 13:45:28 -07:00