nanog mailing list archives
Re: why not AS number based prefixes aggregation
From: Nathan Ward <nanog () daork net>
Date: Tue, 9 Sep 2008 01:36:36 +1200
On 9/09/2008, at 1:20 AM, yangyang. wang wrote:
Hi, everyone:For routing scalability issues, I have a question: why not deploy AS number based routing scheme? BGP is path vector protocol and the shortest paths are calculated based on traversed AS numbers. The prefixes in the sameAS almost have the same AS_PATH associated, and aggregating prefixesaccording to AS will shrink BGP routing table significantly. I don't knowwhat comments the ISPs make on this kind of routing scheme.
I expect you'll see something similar to this in IPv6 long term - most ASes will likely not need to originate more than their RIR 'block' (I can never figure out whether to call it an assignment or an allocation, and whenever I do I seem to get it wrong).
Note that many ASes are expected to intentionally de-aggregate their prefixes. We've so far expected to see this for traffic engineering purposes (ie. to control sharing of load across several different links), however we might see intentional de-aggregation by people attempting to minimise BGP prefix hijacking? Who knows. That's a pretty scary though when considering IPv6..
There was a Cisco slide somewhere (I think originally by Tony Hain?) that had info about that, ie. actual numbers. It's slide 24 (and several slides leading up to it) in the following slide pack by Vince Fuller, but it was old in Feb 2007 when this was put together, so it's even older now - anyone have anything more recent. Anyway, enjoy:
http://www.apricot2016.info/apricot2007/presentation/apia-future-routing/apia-future-routing-vince-fuller.pdf -- Nathan Ward
Current thread:
- why not AS number based prefixes aggregation yangyang. wang (Sep 08)
- Re: why not AS number based prefixes aggregation Nathan Ward (Sep 08)
- Re: why not AS number based prefixes aggregation Scott Brim (Sep 08)
- Re: why not AS number based prefixes aggregation Owen DeLong (Sep 08)
- Re: why not AS number based prefixes aggregation yangyang. wang (Sep 08)
- Re: why not AS number based prefixes aggregation Dave Israel (Sep 08)
- Re: why not AS number based prefixes aggregation Benson Schliesser (Sep 08)
- Re: why not AS number based prefixes aggregation William Herrin (Sep 08)
- Re: why not AS number based prefixes aggregation Christopher Morrow (Sep 08)
- Re: why not AS number based prefixes aggregation Jeroen Massar (Sep 08)
- Re: why not AS number based prefixes aggregation Ricardo Oliveira (Sep 08)
- RE: why not AS number based prefixes aggregation Paul Francis (Sep 08)
(Thread continues...)