I'm starting here with the posit that the global routing table will contain at least one prefix (/48 or shorter in the case of IPv6) from each ASN. Obviously if this doesn't hold, the following discussion isn't valid...
Leaf ASes in the IPv6 world are expected to get a /48 prefix allocation (from an RIR) as they do in the IPv4 world. Given the size of a /48, it's reasonable to expect the vast majority of these ASes will only need a single prefix for IPv6, whereas in IPv4 they might have hundreds. Since these ASes already have an ASN and only need a single prefix, it seems logical to assign a prefix to each AS based on their ASN. This would reduce pressure on the "normal" prefix allocation process used by non-leaf ASes. In fact, a "normal" prefix need only be allocated to a leaf AS when they demonstrate that their ASN-based prefix has been fully utilized or bona fide technical reasons why the AS cannot use a single prefix. A non-leaf AS may (?) use ASN-based addresses for their internal use, but must not assign any such addresses to customers. To reduce advertisements, non-leaf ASes may choose not to use their ASN-based prefix and instead give themselves an internal allocation from one of their "normal" prefixes. Given the number of 16-bit ASNs currently assigned, it seems reasonable to assume an extension to 32-bit ASNs will occur within the lifetime of IPv6. Thus, a single /16 prefix for all ASN-based allocations would be required. The largest problem I see with this is that ASNs are permanently assigned, or at least so far no recovery process is defined and no rent is charged. This means that ASN-based allocations would be similarly permanent. This might be good or bad depending on your view of the RIRs. Thoughts? S Stephen Sprunk "Stupid people surround themselves with smart CCIE #3723 people. Smart people surround themselves with K5SSS smart people who disagree with them." --Aaron Sorkin -------------------------------------------------------------------- IETF IPv6 working group mailing list [EMAIL PROTECTED] Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
