Question about mutual transit and complex BGP peering

Mon Apr 22 14:32:35 UTC 2024

Requesting responses to the following questions. Would be helpful in some IETF work in progress.

Q1: Consider an AS peering relationship that is complex (or hybrid) meaning, for example, provider-to-customer (P2C) for one set of prefixes and lateral peers (i.e., transit-free peer-to-peer (P2P)) for another set of prefixes.  Are these diverse relationships usually segregated, i.e., P2C on one BGP session and P2P on another?  How often they might co-exist within one single BGP session?

Q2: Consider an AS peering relationship that is mutual transit (i.e., P2C relationship in each direction for all prefixes).  Is this supported within one single BGP session?  How often the ASes might setup two separate BGP sessions between them -- one for P2C in one direction (AS A to AS B) and the other for P2C in the opposite direction (AS B to AS A)?

Thank you.

Sriram
Kotikalapudi Sriram, US NIST