Question on the topology of Internet Exchange Points

Thu Feb 14 18:06:55 UTC 2008

kch670 at eecs.northwestern.edu ("Kai Chen") writes:

> A typical Internet Exchange Point (IXP) consists of one or more network
> switches <http://en.wikipedia.org/wiki/Network_switch>, to which each of
> the participating ISPs connect.  We call it the exchange-based topology.
> My question is if some current IXPs use directly-connected topology, in
> which ISPs just connect to each other by direct link, not through a
> network switch?? If so, what's the percentage of this directly-connected
> case?

when i last worked at PAIX, the private interconnects wildly outnumbered
the switch connection.  the model seemed to be, use the switch to reach all
of the other participants, but whenever you had a hot neighbor, get a PNI.

in other words there appeared to be no "exchange-based topology", more like
a "hybrid exchange and PNI topology."
-- 
Paul Vixie