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Date: Thu, 24 Jun 2004 19:13:00 -0500
From: Jon Noack <noackjr@alumni.rice.edu>
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To: "Wilkinson, Alex" <alex.wilkinson@dsto.defence.gov.au>
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cc: Paul Saab <ps@freebsd.org>
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Subject: Re: HEADS UP: SACK committed to HEAD
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On 06/24/04 18:46, Wilkinson, Alex wrote:
> erm .... what is SACK ? I'm assuming ACK is 'acknowledgment ?
> Quick summary anyone ?

Selective ACKnowledgment (for TCP):
http://www.icir.org/floyd/sacks.html
http://www.icir.org/floyd/papers/sacks.pdf

SACK is needed to get decent throughput over high-delay, lossy 
connections (like international links).

Jon Noack

P.S. A google search for "sack acknowledgment" would have given you 
those links as the first hit.  Search engines are your friend.  Part of 
mailing list etiquette is making an attempt to find information for 
yourself...