[49207] in North American Network Operators' Group
Re: how is cold-potato done?
daemon@ATHENA.MIT.EDU (Ralph Doncaster)
Wed Jun 26 14:11:05 2002
Date: Wed, 26 Jun 2002 14:07:52 -0400 (EDT)
From: Ralph Doncaster <ralph@istop.com>
To: Jared Mauch <jared@puck.Nether.net>
Cc: "nanog@merit.edu" <nanog@merit.edu>
In-Reply-To: <20020626175417.GC8576@puck.nether.net>
Errors-To: owner-nanog-outgoing@merit.edu
> > If I peer with network X in cities A and B, and receive the same route in
> > both cities with an AS-path of X, how do I know which city to use for an
> > exit? I can understand how if X uses communities to tag the geographic
> > origin of the traffic, but I'm not aware of many networks that do
> > this. Lots of networks claim to use cold-potato routing though, so how do
> > they do it?
>
> they use the MED sent on the route (aka metric) from the
> other provider to determine which exit where they both interconnect
> is the "shortest".
>
> this can at times provide undesired results because of
> aggregation.
Besides aggregation, wouldn't this lead to a lot of ties?
Let's say the cities are LA & Manhattan, and the route from X originates
in Chicago. I would think that it would be a common occurrance for the
route to have the same metric in LA & Manhattan.
-Ralph
