North American Network Operators Group
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Re: packet reordering at exchange points

  • From: Peter Galbavy
  • Date: Wed Apr 10 10:50:50 2002 
> 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