Re: 3177-bis

[Geoff Huston <gih@apnic.net>]

Tony Hain wrote:
> I agree it is the total number of prefixes that matter, and moving the bits
> from the site to the DFZ side of the default allocation unit will amplify
> the number of possible prefixes that the global routing system has to carry.
> Since we know the RIR policy will continue to be as stingy as possible,
> there will be fragmentation over time, so more bits just means a bigger
> scaling problem. 

The number of possible prefixes that the global routing system has to carry could perhaps be more appropriately be phrased as 2 **32, as this discussion is about end site prefix sizes, not the size of minimum allocations to providers.

Address allocation policies in the RIRs have attempted to ensure maximal aggregation capability by setting the minimum provider allocation size as a /32. Using an HD ratio of 0.94 and a /56 end site size that comes to 6,183,533 end site allocations from a /32, or much the same as a /9 allocation in IPv4 terms.

I'm not exactly sure how such an approach is "stingy", nor can I understand how such an approach of making minimum allocations span such networks appears to intrinsically exacerbate routing fragmentation

AS an aside, if the issue that matters is the potential impact on the routing system, then the experience to date is that the size of the routing system is related to the number of entities who express distinct routing policies and the density of interconnection between these entities. 

Geoff