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
_______________________________________________
NANOG mailing list
https://lists.nanog.org/archives/list/[email protected]/message/GACH2AEI347BNJIK3JORGZTM3CYE4KD2/
