[52537] in North American Network Operators' Group
Re: UUNET Routing issues
daemon@ATHENA.MIT.EDU (Petri Helenius)
Thu Oct 3 18:20:07 2002
From: "Petri Helenius" <pete@he.iki.fi>
To: "Iljitsch van Beijnum" <iljitsch@muada.com>,
"Marshall Eubanks" <tme@multicasttech.com>
Cc: <nanog@merit.edu>
Date: Fri, 4 Oct 2002 01:19:54 +0300
Errors-To: owner-nanog-outgoing@merit.edu
> 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.
>
Vendor C sells packet memory up to 256M each way for a line card. Whether
this makes any sense depends obviously on your interfaces. Theoretically
it makes sense to be able to accommodate the number of flows youŽre carrying
times the window size advertised by TCP. In live networks not too large
a percentage of the flows send data at maximum so one would expect to have
a few thousand "full" flows on a link at time. 64k window for thousand flows
would use 64M buffer memory. (not counting memory utilization inefficiencies)
If you go deeper into the equation and start to analyze how fast youŽll get the
packets
in anyway, the associated mathematics will require a significantly longer
presentation
which youŽll probably find easily by Google.
Pete
