North American Network Operators Group
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Re: NANOG 40 agenda posted

  • From: Donald Stahl
  • Date: Sat Jun 02 17:09:25 2007

[Update to earlier stats: The current v4 prefix/AS ratio is 8.7.
However, there are ~11k ASes only announcing a single v4 route, so that means the other ~14k ASes are at a v4 ratio of 14.3. In contrast, the current v6 ratio is 1.1 and the deaggregate rate is 1.2%.]
This is more than a little frightening :(

The simplistic answer is that nearly all assigned/allocated blocks will be minimum-sized, which means ISPs will be capable of filtering deaggregates if they wish. Some folks have proposed allowing a few extra bits for routes with short AS_PATHs to allow TE to extend a few ASes away without impacting the entire community.
This is an excellent solution- is there some reason people wouldn't want to implement it? It would seem to lead directly to a more heirarchical table.

justification for larger-than-minimum blocks. OTOH, the community may see how small the v6 table is and decide that N bits of deaggregation wouldn't hurt. After all, with ~25k ASes today, and router vendors claiming to be able to handle 1M+ routes, it seems we could tolerate up to 5 bits of deaggregation -- and 3 bits would leave us with a table smaller than v4 has today.
Combine this with the above system. Allow 2 bits of deagg anywhere but up to 4 bits for a short as_path for networks in the /48 range. Allow 3 bits for networks in the /32 range and up to 5 bits for a short as_path. (or whatever other numbers make sense).

Either way we seem to be looking at a much smaller table as long as we decide on some sensible rules and actually stick to them. That is going to be the biggest problem though.

-Don