[routing-wg]a (perhaps) naive question...

Well, if the AS-set doesn't fit, that's a problem.

But it isn't necessarily the case that simply because an AS that gets, say,
RIPE addresses is transcontental means that it can't be part of a "RIPE"
aggregate.  One would have to sit down and see how bad the paths are relative
to the RIB savings.  I don't suppose anyone has done such a study?

PF
  

> -----Original Message-----
> From: Florian Weimer [mailto:fw at deneb.enyo.de] 
> Sent: Monday, September 29, 2008 7:31 PM
> To: Paul Francis
> Cc: Routing WG
> Subject: Re: [routing-wg]a (perhaps) naive question...
> 
> * Paul Francis:
> 
> > I was wondering the other day why we don't do aggregating 
> in BGP along 
> > the lines of registry assignments.  For instance, what 
> stops the set 
> > of ISPs within Europe from from taking the 15 or 20 
> prefixes given to 
> > RIPE by IANA, and collectively aggregating those prefixes when 
> > advertising to non-RIPE ISPs?  It seems to me that they could 
> > advertise all of their AS#'s as a huge AS-set for these prefixes.
> 
> The latter probably doesn't work because the AS set size 
> would exceed the maximum size of a BGP UPDATE message.  The 
> number of prefixes is also large than 20 due to the pre-RIR 
> swamp space.
> 
> > Is there a technical issue that prevents this, or does the 
> > organizational effort needed simply outweigh the benefit that would 
> > accrue?
> 
> It leads to worse routing decisions and does not reflect the 
> reality of autonomous systems spanning multiple continents.  
> (Anyone who is multi-homed to one of those trans-continentals 
> would probably need a globally visible prefix.)
> 
> Actually, for ISPs in the RIPE region, it would make more 
> sense to aggregate the prefixes of ISPs *not* in the RIPE region.
>