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To: mag@intron.ac
From: Mark Allman <mallman@icir.org>
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Date: Tue, 23 May 2006 09:07:45 -0400
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Cc: freebsd-net@freebsd.org, Marcin Jessa <lists@yazzy.org>
Subject: Re: How to Quicken TCP Re-transmission? 
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> 1. Receiver should tell sender to re-send as soon as possible.
>    (But TCP makes receiver purely passive)

This isn't really going to help you at all.  With SACK (especially, but
even without it) the receiver isn't really in a whole lot better
position than the sender to judge when a packet is actually lost.  Some
people have worked on SNACKs (selective NEGATIVE acknowledgments), but
my opinion is that the results (that I have seen) show them to be fairly
equivalent to SACK in terms of performance.

> 2. Receiver should tell sender what is really necessary to re-send.
>    (Sometimes only a single ACK number of TCP cannot include enough
>     information)

RFC2018.  (Which provides more than a single ACK number.  But, this
doesn't make the receiver tell the sender what to resend.  The logic
still resides at the sender.)

allman




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