No, that's not the situation being discussed. As I've pointed out, a multi homed AS without an IGP connecting all prefixes is non-compliant with the BGP definition of an AS. Your Tokyo/DC example is additionally non-compliant because it doesn't have a single routing policy. It has two policies. That this may work in certain circumstances doesn't make it compliant with the standard. I can stop a car by throwing out a boat anchor, but that doesn't comply with DOT standards for braking :) ________________________________ From: Valdis Kletnieks <valdis@vt.edu> on behalf of Valdis Klētnieks <valdis.kletnieks@vt.edu> Sent: Thursday, May 30, 2019 5:58:34 PM To: Mel Beckman Cc: Thomas Bellman; nanog@nanog.org Subject: Re: BGP prefix filter list On Fri, 31 May 2019 00:10:42 -0000, Mel Beckman said:
What are you talking about? Do you use multi homed BGP? If so, I???d expect you to know that an organization with multiple sites having their own Internet still uses a single AS. They have IGP paths to route traffic between sites (e.g., by using dedicated circuits).
The situation being discussed is an organization with multiple sites that *don't* have a behind-the-scenes dedicated circuit, tunnel, or other interconnect. For example, XYZ Corp has a POP in Tokyo announcing a /16 to their provider there, and a POP in DC announcing a different /16 to their North American provider, using the same ASN for both - but traffic between the two /16s traverses the commodity Internet. Or they advertise the same /16 and pray to the anycast gods. :) (Actually, that's OK too, as long as both Tokyo and DC also announce a second route (possibly a more-specific, or different address space) for their interconnect needs)