Re: [Idr] Progressing draft-bhatia-bgp-multiple-next-hops-01.txt

[Paul Jakma <paul at clubi.ie>]

On Thu, 24 Aug 2006, Enke Chen wrote:

> > RR1 would advertise the following UPDATEs to RR2.
> >
> > UPDATE: feasible nlri X, next_hop N1, <other attributes>
> > UPDATE: feasible nlri X, multiple_hop N11, <other attributes>
> > UPDATE: feasible nlri X, multiple_hop N2, <other attributes>
> > UPDATE: feasible nlri X, multiple_hop N22, <other attributes>
>
> Please note that B1 and B2 are clients and do not advertise 
> multi-paths.  How do (X, N1) and (X, N2) got withdrawn on RR2 as 
> they are no longer valid (replaced by B1 and B2), in other words 
> how does RR2 figure out (X, N11) is a replacement of (X, N1), and 
> (X, N22) a replacement of (X, N2)?

They don't need to.

The first above, with NEXT_HOP (or MP_REACH for MP) continues to 
imply a full implicit withdrawal of the NLRI. So with that first 
UPDATE all the previous (NLRI,nexthops) are withdrawn.

Further, if <other attributes> are the same for the above paths, it 
can be done in just one UPDATE.

UPDATE: feasible nlri X,
        NEXT_HOP N1,
	MULTIPLE_HOP N11, N2, N22
	<other attributes>

If, say, all but (X,N22) had the same attributes, then the following 
would be sent:

UPDATE: feasible nlri X,
        NEXT_HOP N1,
	MULTIPLE_HOP N11, N2
	<other attributes>
UPDATE: feasible nlri X,
	MULTIPLE_HOP N22
	<(X,N22) attributes>

regards,
--
Paul Jakma	paul at clubi.ie	paul at jakma.org	Key ID: 64A2FF6A
Fortune:
Snow Day -- stay home.

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