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Date:      Wed, 17 Jul 2002 21:13:00 -0700
From:      Bakul Shah <bakul@bitblocks.com>
To:        Garrett Wollman <wollman@lcs.mit.edu>
Cc:        "Greg 'groggy' Lehey" <grog@lemis.com>, cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG
Subject:   Re: Retransmission timeouts (was: cvs commit: src/sys/netinet tcp_timer.h) 
Message-ID:  <200207180413.AAA17978@thunderer.cnchost.com>
In-Reply-To: Your message of "Wed, 17 Jul 2002 23:18:08 EDT." <200207180318.g6I3I8hj000996@khavrinen.lcs.mit.edu> 

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> I've found it: it's (obliquely) in the Allman and Paxson paper
> referenced in the commit logs.  Implementations are allowed to delay
> ACKs for as long as 500 ms.

RFC1122 section 4.2.3.2 says a TCP SHOULD implement delayed
ACKs but the delay shouldn't be excessive and MUST be less
than 0.5 seconds.

In section 4.2.3.1 it also says that "The lower bound (of the
RTO) SHOULD be measured in fractions of a second (to
accommodate high speed LANs)".  Though it is not the speed
but the latency that matters.

> Network speeds have practically nothing to do with a correct
> implementation of the TCP protocol.

I agree on the whole but IMHO "correct" is too strong a word.
No reason TCP should stop evolving now.

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