From: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
To: Oumer Teyeb <oumer@kom.aau.dk>
Cc: netdev@vger.kernel.org
Subject: Re: Weird TCP SACK problem. in Linux...
Date: Fri, 21 Jul 2006 03:23:04 +0400 [thread overview]
Message-ID: <20060720232304.GA21573@ms2.inr.ac.ru> (raw)
In-Reply-To: <44BE5E89.1020002@kom.aau.dk>
Hello!
> Hmmm... I dont understand this....so if reording can be detected, (i.e
> we use timestamps, DSACK), the dupthreshold is increased
Yes.
> implementation that might lead to increase in the number of
> retransmissions, but leads to improvment in download time
Hmm... I thought and still do not know.
> couldnt figure it out,....also is there anywhere where the reordering
> response of tcp linux described? (it seem dupthreshold is dynamically
> adjusted based on the reordering history... but I was not able to find
> out how...)...
That's comment from tcp_input:
* Reordering detection.
* --------------------
* Reordering metric is maximal distance, which a packet can be displaced
* in packet stream. With SACKs we can estimate it:
*
* 1. SACK fills old hole and the corresponding segment was not
* ever retransmitted -> reordering. Alas, we cannot use it
* when segment was retransmitted.
* 2. The last flaw is solved with D-SACK. D-SACK arrives
* for retransmitted and already SACKed segment -> reordering..
Alexey
prev parent reply other threads:[~2006-07-20 23:23 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-07-18 19:38 Weird TCP SACK problem. in Linux Oumer Teyeb
2006-07-19 9:38 ` Xiaoliang (David) Wei
2006-07-19 10:00 ` Oumer Teyeb
2006-07-19 13:27 ` Alexey Kuznetsov
2006-07-19 15:02 ` Oumer Teyeb
2006-07-19 15:49 ` Alexey Kuznetsov
2006-07-19 16:32 ` Oumer Teyeb
2006-07-19 17:32 ` Oumer Teyeb
2006-07-20 15:41 ` Oumer Teyeb
2006-07-20 23:23 ` Alexey Kuznetsov [this message]
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