[1289] in North American Network Operators' Group
Re: Sprint BGP filters in 207.x.x.x?
daemon@ATHENA.MIT.EDU (Curtis Villamizar)
Fri Dec 15 21:59:19 1995
To: Jeremy Porter <jerry@fc.net>
cc: bmanning@isi.edu, nanog@merit.edu
Reply-To: curtis@ans.net
In-reply-to: Your message of "Thu, 14 Dec 1995 01:26:19 CST."
<199512140726.BAA08568@freeside.fc.net>
Date: Fri, 15 Dec 1995 21:53:05 -0500
From: Curtis Villamizar <curtis@ans.net>
In message <199512140726.BAA08568@freeside.fc.net>, Jeremy Porter writes:
> >>If we had a good method for people to indicate routes that they didn't want
> to
> >>be aggregated, then more proxy aggregation could be done safely.
> >>
> >
> > If I may... The idea of using a routing registry for
> > this purpose has been suggested before. I still think
> > it is a valid approach. Could be very useful in assisting
> > with better proxy aggregation for all.
>
> Let me just say I think the RR has some good uses, i.e.
> finding out what people intended the routing to look like, etc.
>
> I don't really understand how a RR can help with proxy aggregation
> seeing as the route objects really only provide origin AS
> and regular aggregation.
The additional clues can be found in the aut-num for dual homed AS.
If a route is registered with more than one origin AS and you route
differently to these two AS, that's a clue to look carefully before
proxying too.
> It seems to me dual homed sites which are the concence of
> proxy aggregation, can be detected with a reasonably full set
> of routes, i.e. the second from AS from the origin in the ASPATH
> being different. (Or some split in the path outside of an
> AS communinity or confederation).
The secondary route may not be advertised to you if the primary
suppresses the advertisement. For example if previders are A and B
and they peer with each other, I may think I can aggregate some prefix
over provider A, but B may not be advertising a backup path since it
is preferring the same primary through A.
Curtis
