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Date:      Mon, 2 Oct 2000 15:53:30 +0200 (CEST)
From:      Luigi Rizzo <luigi@info.iet.unipi.it>
To:        Julian Elischer <julian@elischer.org>
Cc:        net@FreeBSD.ORG
Subject:   Re: SACK in FreeBSD TCP.
Message-ID:  <200010021353.PAA47114@info.iet.unipi.it>
In-Reply-To: <Pine.BSF.4.10.10010020644350.36257-100000@InterJet.elischer.org> from Julian Elischer at "Oct 2, 2000 06:48:53 am"

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> Is anyone working on a SACK  (Selective acknowlegement) implementation
> for FreeBSD?
> 
> (rfc 2018)
> 
> It would make a huge difference to performance out here at the edge of the
> univertse (Perth, Western Australia)

I wonder if the "huge difference" is for real or just a myth.

When i did some work on sack back in 1996 (including a FreeBSD
implementation, see http://www.iet.unipi.it/~luigi/sack.html
I did not find that SACK to be such a panacea. Basically,
most connections under high loss still had a tendency to
stall because the window would never open enough to have 3dupacks
which would trigger a retransmission...

	cheers
	luigi
-----------------------------------+-------------------------------------
  Luigi RIZZO, luigi@iet.unipi.it  . Dip. di Ing. dell'Informazione
  http://www.iet.unipi.it/~luigi/  . Universita` di Pisa
  TEL/FAX: +39-050-568.533/522     . via Diotisalvi 2, 56126 PISA (Italy)
  Mobile   +39-347-0373137
-----------------------------------+-------------------------------------


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