classful routes redux

Sat Nov 5 17:01:41 UTC 2005

At 03:09 AM 5/11/2005, Christopher L. Morrow wrote:

>On Fri, 4 Nov 2005, Russ White wrote:
> >
> > - -- BGP is currently moving to a 2^32 space for AS numbers. That's odd,
> > if there's only 18,044 origins in the current table, and it won't ever
> > grow to much more--how'd we lose 40,000 or so AS numbers, that we now
> > need more than 64,000?
>
>I think someone at CAIDA or even Renesys could put out some good numbers
>for 'origin' AS counts and even 'AS in aspath' It's slightly higher than
>18k, but not 40k higher :) At last look (during arin/nanog meeting) it was
>about 20k unique origins (from 701 perspective as seen through
>routeviews)

As of a few minutes ago there are 21.042 unique ASs seen in Route-Views.

13,997 are origin onlu (i.e. they are not seen in the middle of an AS 
path), 66 are transit only and 6.979 are mixes origin  + transit.

8,554 ASs announce a single prefix, while the average announcements per 
origin AS is 9.1 (the reason is a heavy tail distribution where a small 
number of ASs originate a very large number of prefixes)

The average address span for an origin AS is 70,426 /32s (or slightly 
larger than a /16) Again this is a heavy tail distribution.

(more time series data on the routing table than you'd ever want is at 
http://bgp.potaroo.net/as4637/ and http://bgp.potaroo.net/as6447)

The overall trend is the association of fewer addresses per originating AS, 
pointing to a trend to impose ever finer levels of policy delineation 
within the inter-domain routing mesh at places closer to the edge of the 
network - i.e. multi-homing and traffic engineering within an increasingly 
dense interconnection mesh appear to be one of the major motivations here 
for the continued consumption of AS numbers. The CAIDA skitter graphs are 
perhaps the most dramatic way I've encountered so far that clearly shows 
this trend.

regards

    Geoff