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Date: Fri, 27 Apr 2007 16:25:19 -0400 (EDT)
From: Mike Silbersack <silby@silby.com>
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To: Preethi Natarajan <nataraja@cis.udel.edu>
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Cc: freebsd-net@freebsd.org, "Paul D. Amer" <amer@cis.udel.edu>
Subject: Re: TCP Delayed Ack implementation in 6.1
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On Fri, 27 Apr 2007, Preethi Natarajan wrote:

>  From tcpdump at client side:
> Time: 38s.695ms: S->C data (282b)
> Time: 38s.707ms: S->C data (1448b)
> Time: 38s.707ms: C->S ack
> Time: 38s.719ms: S->C data (1448b)
> Time: 38s.719ms: C->S ack
> Time: 38s.731ms: S->C data (1448b)
> Time: 38s.741ms: S->C data (1166b)
> Time: 38s.741ms: C->S ack
>
> I do not understand the reason for the second ack from C->S (Time
> 38s.719ms). Clearly this ack has not delayed for 200ms from the previous
> ack and acks only 1 packet. Am I missing something?
>
> Thanks a ton,
> Preethi

My crystal ball tells me that packet four has the PUSH flag set on it,
which means that it will be immediately ACKed and sent to the application.

Please post tcpdump output in the future, the batteries on my crystal ball
are running low.

Mike "Silby" Silbersack