*BSD News Article 73883


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From: souva@aibn58.astro.uni-bonn.de (Ignatios Souvatzis)
Subject: TCP latency in the presense of RFC1323 (Was: Re: TCP latency)
In-Reply-To: matt@3am-software.com's message of 14 Jul 1996 22:12:43 GMT
Message-ID: <SOUVA.96Jul16132215@aibn58.astro.uni-bonn.de>
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Organization: Radioastronomisches Institut der Universitaet Bonn, Bonn, FRG
References: <4paedl$4bm@engnews2.eng.sun.com> <4rlf6i$c5f@linux.cs.helsinki.fi>
	<31DEA3A3.41C67EA6@dyson.iquest.net> <Du681x.2Gy@kroete2.freinet.de>
	<31DFEB02.41C67EA6@dyson.iquest.net>
	<4rpdtn$30b@symiserver2.symantec.com>
	<x7ohlq78wt.fsf@oberon.di.fc.ul.pt>
	<Pine.LNX.3.91.960709020017.19115I-100000@reflections.mindspring.com>
	<x74tnfn35s.fsf@oberon.di.fc.ul.pt>
	<4s33mj$fv2@innocence.interface-business.de>
	<4sbrcr$rqd@enomem.lkg.dec.com>
Date: Tue, 16 Jul 1996 11:22:15 GMT
Lines: 28
Xref: euryale.cc.adfa.oz.au comp.os.linux.networking:45398 comp.unix.bsd.netbsd.misc:4073 comp.unix.bsd.freebsd.misc:23722

In article <4sbrcr$rqd@enomem.lkg.dec.com> matt@3am-software.com (Matt
Thomas) writes:

   There are a number of problems with the way timers are implemented
   in TCP.  The first is granularity.  A slow/fast timeout has an
   inaccuarcy of up to 500ms/200ms.  That may cause inaccuaries to creep
   into round-trip estimates.

Shouldn't this be unimportant in the presence of the RFC1323 round
trip _measurement_ (instead of "educated guessing", which old BSD TCP
did)? 

Which reminds me of: Did anybody ever analyze why some (old?) Linux
boxes would damage RFC1323 TCP packets routed through them? Only
change to pre-rfc1323 would be in the TCP part, so maybe it is a
problem in the os-specific part of the ppp implementation in Linux?
(Assuming that no other part of the networking code violates
layering). 

Regards,
	Ignatios Souvatzis


-- 
	Ignatios Souvatzis
Cute quote: "You should also consider that the ST comes fully equipped with a 
	     text adventure. It's called ST Basic." Amylaar@meolyon.hanse.de