[52540] in North American Network Operators' Group
Re: UUNET Routing issues
daemon@ATHENA.MIT.EDU (Stephen Sprunk)
Thu Oct 3 18:34:40 2002
From: "Stephen Sprunk" <ssprunk@cisco.com>
To: "Iljitsch van Beijnum" <iljitsch@muada.com>,
"Marshall Eubanks" <tme@multicasttech.com>
Cc: <nanog@merit.edu>
Date: Thu, 3 Oct 2002 17:32:32 -0500
Errors-To: owner-nanog-outgoing@merit.edu
Thus spake "Iljitsch van Beijnum" <iljitsch@muada.com>
> At 155 Mbps you need 32 MB worth of buffer space to arrive at a delay like
> this. I wouldn't put it past ATM vendors to think of this kind of
> over-enthusiastic buffering as a feature rather than a bug.
Traditionally, it's ATM switches that have tiny buffers and routers that have
excessive buffers. ATM networks have closed-loop feedback and ingress policing
mechanisms to handle this scenario; IP networks just throw buffers at the
problem and hope it works.
> Does anyone have any thoughts on optimum buffer sizes?
The "correct" amount of buffer space for a link is equal to its bandwidth-delay
product. Unfortunately, this requires per-link testing and configuration on the
part of the operator, which is extremely rare.
S
