[46763] in North American Network Operators' Group
Re: packet reordering at exchange points
daemon@ATHENA.MIT.EDU (Peter Galbavy)
Wed Apr 10 10:49:17 2002
Message-ID: <016501c1e09e$cf233450$2028a8c0@carpenter>
From: "Peter Galbavy" <peter.galbavy@knowtion.net>
To: "Richard A Steenbergen" <ras@e-gerbil.net>,
"E.B. Dreger" <eddy+public+spam@noc.everquick.net>
Cc: "Paul Vixie" <paul@vix.com>, <nanog@merit.edu>
Date: Wed, 10 Apr 2002 15:48:36 +0100
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> To transfer 1Gb/s across 100ms I need to be prepared to buffer at least
> 25MB of data. According to pricewatch, I can pick up a high density 512MB
Why ?
I am still waiting (after many years) for anyone to explain to me the issue
of buffering. It appears to be completely unneccesary in a router.
Everyone seems to answer me with 'bandwidth x delay product' and similar,
but think about IP routeing. The intermediate points are not doing any form
of per-packet ack etc. and so do not need to have large windows of data etc.
I can understand the need in end-points and networks (like X.25) that do
per-hop clever things...
Will someone please point me to references that actually demonstrate why an
IP router needs big buffers (as opposed to lots of 'downstream' ports) ?
Peter
