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Date:      Fri, 12 Mar 2004 07:41:12 +0200
From:      Petri Helenius <pete@he.iki.fi>
To:        David Malone <dwmalone@maths.tcd.ie>
Cc:        Mark Allman <mallman@icir.org>
Subject:   Re: Who wants SACK? (Re: was My planned work on networking stack)
Message-ID:  <40514D78.6020605@he.iki.fi>
In-Reply-To: <20040311225347.GA66644@walton.maths.tcd.ie>
References:  <20040310192255.GD14892@Odin.AC.HMC.Edu> <20040310193840.6479F77A6D4@guns.icir.org> <20040311225347.GA66644@walton.maths.tcd.ie>

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David Malone wrote:

>Mind you, Petri originally asked about evidence for two machines
>back-to-back, and 100ms is rather long for that (unless you're at
>Steven Low's lab ;-)
>  
>

Another interesting figure which comes to mind is whether "bursty loss" 
is the usual way a multigigabit optical link loses IP packets or if the 
flipping of single bit hits only one packet. This influences the actual 
real life problem a lot and in my understanding of 8B/10B coding, itīs 
designed not to lose sync over a single bit error so with a probability 
of bit error every few minutes, hitting two in close succession (in the 
window) is unlikely.

Some time ago we did experiments implementing FEC at IP layer to make 
the multimedia which run over the network zero loss. While doing the 
experiment we recognized that the clustered loss we saw was caused by 
software issues in routers, not at any transmission devices. Using 
somewhat deeper interleaving of packets solved the issue with this 
application.

Pete



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