why not AS number based prefixes aggregation

Paul Francis francis at cs.cornell.edu
Mon Sep 8 14:31:18 CDT 2008

This thread begs an interesting question:  what is the right amount of
granularity for load balance?  Folks here are saying that one-entry-per-AS is
too course...an AS wants to influence load on incoming links, and so it needs
multiple entries.

On the other hand, it is hard to imagine that we need hundreds of entries per
AS, or even dozens.  So I'm curious...if we could wave a magic wand and
control the exact number of entries any AS needs to advertise, what would
folks consider to be roughly the right number of entries?




> -----Original Message-----
> From: Ricardo Oliveira [mailto:rveloso at cs.ucla.edu] 
> Sent: Monday, September 08, 2008 1:11 PM
> To: nanog at merit.edu
> Subject: Re: why not AS number based prefixes aggregation
> Topological aggregation based on ASN is often too course 
> granularity, see this paper:
> http://www.cs.ucla.edu/~rveloso/papers/giro.pdf
> specifically Fig4 is a good example, and sec 4C.
> Cheers,
> --Ricardo
> On Sep 8, 2008, at 6:20 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 same AS almost have the same AS_PATH 
> associated, and 
> > aggregating prefixes according to AS will shrink BGP routing table 
> > significantly. I don't know what comments the ISPs make on 
> this kind 
> > of routing scheme.
> >
> >
> > -yang

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