[46712] in North American Network Operators' Group
Re: packet reordering at exchange points
daemon@ATHENA.MIT.EDU (Valdis.Kletnieks@vt.edu)
Mon Apr 8 21:59:27 2002
Message-Id: <200204090157.g391vN6H025714@foo-bar-baz.cc.vt.edu>
To: Iljitsch van Beijnum <iljitsch@muada.com>
Cc: Paul Vixie <paul@vix.com>, nanog@merit.edu
In-Reply-To: Your message of "Tue, 09 Apr 2002 00:32:50 +0200."
<20020409002240.X76423-100000@sequoia.muada.com>
From: Valdis.Kletnieks@vt.edu
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Date: Mon, 08 Apr 2002 21:57:23 -0400
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On Tue, 09 Apr 2002 00:32:50 +0200, Iljitsch van Beijnum said:
> Obviously some applications care. In addition to the examples mentioned
> earlier: out of order packets aren't really good for TCP header
> compression, so they will slow down data transfers over slow links.
On the other hand, wouldn't this sort of slow link tend to close down
the TCP window and thus tend to minimize the effect? A quick back-of-envelope
calculation gives me a 56K modem line only opening the window up to 10K
or so - so there should only be 5-6 1500 byte packets in flight at a given
time, so the chances of *that flow* getting out-of-order at a core router
that's flipping 200K packets/sec are fairly low.
Not saying it doesn't happen, or that it isn't a problem when it does - but
I'm going to wait till somebody posts a 'netstat' output showing that
it is in fact an issue for some environments...
--
Valdis Kletnieks
Computer Systems Senior Engineer
Virginia Tech
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