I believe that the optimal configuration would actually involve only
one routing entity and no peering at all. I'm pleased that instead
we've implemented a model which (while not optimal) allows for a
growing Internet service provider industry. Solutions which are
optimal under one constraint tend to degenerate in the real world.
Shortest-exit routing and equivalent distributed peering is used to
avoid settlements for transit costs. If there's a strong demand
for dissimiliar peering, then it's likely to appear with settlements.
/John
>...
>Setting aside the technological barriers to such an arrangement, an
>optimal configuration would be one in which all routing entities peer with
>one another at all available locations, so as to provide the shortest path
>between routing communities.
I believe that the optimal configuration would actually involve only
one routing entity and no peering at all. I'm pleased that instead
we've implemented a model which (while not optimal) allows for a
growing Internet service provider industry. Solutions which are
optimal under one constraint tend to degenerate in the real world.
For varying values of "optimal". 
In terms of decision-making, you
can't beat centralized routing...if a single entity knows all there is to
know about current state of the Internet topology, it can make optimal
decisions. But a distributed system is far more reliable, and more
flexible in terms of growth. My "optimal" was slightly more oriented
toward the current state of affairs than was yours. 
Shortest-exit routing and equivalent distributed peering is used to
avoid settlements for transit costs. If there's a strong demand
for dissimiliar peering, then it's likely to appear with settlements.
I, for one, would see this as a far more equitable solution than an SKA
arrangement where peering arrangements are subject to strict policy-based
discrimination.
If I were to peer with Sprint at MAE-East (and MAE-east only), relying on
their network to backhaul traffic across the nation, it could be seen as
fair for me to compensate them financially, if only as an interim measure
until a true peering arrangement is feasible.
// Matt Zimmerman Chief of System Management NetRail, Inc.
// mdz@netrail.net sales@netrail.net
// (703) 524-4800 [voice] (703) 524-4802 [data] (703) 534-5033 [fax]