NANOG 40 agenda posted

Donald Stahl don at
Sat Jun 2 21:07:17 UTC 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 

> 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.


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