Saku Ytti via NANOG писал(а) 2025-08-24 03:27:
Thinking bit more this. If we had ended up in solution something like this, which enforces joint AS:prefix relation. Our lookup engines likely would be very different, because we could have gotten away with some sort of inter domain MPLS, with 'AS labels', doing exact match AS lookups, instead of LPM IP while in transit and LPM only in edges.
This can be done already, relatively easily inside one AS, but definitely will hit a scalability barrier if expanded between ASes globally. If implemented it will create more instability, because if the path changes inside neighbor AS to another outgoing interface to the same next AS, it will trigger a label change upstream/downstream depending on PoV. In any case LPM will still be necessary on every ingress node to find a prefix for a particular /32, or on a next aggregation node if the ingress node uses default route. Regarding link-state, the number of objects in this database will be much bigger than in current BGP table. The number of BGP paths now is roughly the same an the number of prefixes in DMZ. It probably will be multiplied by number of transit links to each AS, plus some peering links, etc. I see that underneath it's a neat idea to use AS numbers as principal routing objects, but in current reality it's an IP address that identifies the destination, so the lookup to find AS for a particular prefix has to be done and the routing table for this lookup has to be maintained. The idea when it could scale better is to certain extend present in v6, but in reality very far from that with the existing implementation. It could be though a principle for a new IP version if it ever be invented. Kind regards, Andrey