The question above is rather interesting, and what I'd like to know is
what are the various types of "peering" that various ISPs have arranged
between each other?
PEERING == Equal relation ship wher provider A announces routes to themselves
and their customers to provider B and Provider B does likewise. There is
no announcement by either party of non-customer 3rd party routes to the other.
TRANSIT == Provider A is a customer of provider B. Provider A announces
routes to itself and it's customers. Provider B announces a complete routing
table and/or a default route to provider A.
These are separate and distinct entities from Exchange points... Exchanges
(places where traffic gets handed off) come in the following varieties:
PUBLIC == An exchange point where multiple providers connect with each other
across a shared media, such as ATM, FR, Ethernet, FDDI, etc. Generally most
public exchanges are run by a third party to whom all of the ISPs connecting
have a customer relationship.
PRIVATE == A circuit or virtual circuit between two providers which does not
provide a shared media type of environment with multiple providers. Generally,
there is no third party customer relationship, other than possibly one or both
ISPs paying a telco for a circuit.
There are many different financial arrangements that can be made around private
peering. One of the most common ones I've seen is to bring up multiple circuits
and agree that provider A pays for one circuit while provider B pays for the
other. No other money changes hands.
Sometimes, provider A is willing to pay for all circuits just to get better
connectivity for their customers.
I hope this clarifies the terms.