Re: how is cold-potato done?

[Ralph Doncaster]

> > 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