Messages in this thread |  | | | Date | Wed, 11 Nov 1998 16:42:23 -0800 | | From | "David S. Miller" <> | | Subject | Re: TCP, congestion window & retransmission |
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Date: Wed, 11 Nov 1998 17:31:37 +0100 (CET) From: Andrea Arcangeli <andrea@e-mind.com>
According to the RFC2001 in case of duplicate acks or timeout TCP has to do slow-start until TCP has not the congestion window open to the value of sstresh (set to max(cwnd/2,1) before -> at timeout time). When the congestion window is >= sstrash, TCP must go in congestion avoidance incrementing cwnd of segsize*segsize/cwnd and at most incrementing of 1 unit every RTT (this way cwnd increase liner and not exponential).
rfc2001.bis draft clarifies the issue here, and states that our current behavior is in spec. The idea is that if you don't increase the congestion windows at all during timeout based retransmissions, this is being concervative and is OK. A copy of this draft is available from:
ftp://ftp.ietf.org/internet-drafts/draft-ietf-tcpimpl-cong-control-01.txt
In any event, it's bad for performance not to do the congestion window increases, so I've made the "fix" in tcp_input.c which I'll send to Linus shortly.
Later, David S. Miller davem@dm.cobaltmicro.com
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