Along these lines, one could leave the transit AS networks alone if a parallel 16 bit ASN space were created. Essentially, any non-transit network would have it's non-public ASN retranslated NAT-style by upstream transit network border routers. Only the border routers would have to be changed. They would have to differentiate between public ASN X and non-public ASN X (same number) based on the which side of the router the ASN was learned from. This would essentially double the ASN numbers available. All that being said, I'd much rather see 32-bit ASNs. John At 10:48 AM 12/3/2004, Edward B. Dreger wrote:
Perhaps transit networks should receive 16-bit ASNs. Leaf networks would use { a special ASN | I'm still brainstorming | who knows } and carry an "available upstreams" BGP tag for each upstream.
Metrics are calculated for each transit AS. Those metrics are then combined with <as yet unspecified intelligence in "available upstreams" tag> for each leaf ASN.
BGP loop detection might present a problem if all leaf ASNs use, say, 16-bit AS65535. If existing allowas-in is too coarse, refer to "32-bit ASN" BGP attribute for fine-grained control.
In short: I'm trying to think up a mechanism that performs full Dijkstra calculations _only_ for transit networks, and uses some cheaper version for the degenerate case of a leaf network.
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