Re: [Idr] draft on virtual aggregation

[Daniel Ginsburg <dg at ot-e.biz>]

Paul Francis wrote:
> Its posted by IETF now.  At
> http://www.ietf.org/internet-drafts/draft-francis-idr-intra-va-00.txt

Paul,

I think that there're few problems with the draft.

One is with PHP. If a router is a border VA router, it must perform 
*ultimate*-hop-popping, not penultimate as section 3.2.3 of the draft 
states, since the router is egress for an LSP (as per RFC5036 
terminology). I.e. it means that a border VA router must not advertise 
implicit (or explicit) null label for FECs corresponding to external 
next-hops. Also section 3.2.3 implies that external next-hops must be 
carried inside AS' IGP, and IMHO the draft should explicitly say so.

Another problem is mixing legacy hop-by-hop forwarding and VA. Consider 
the following topology.

    10
A--------B
|        |
|100     | 10
|        |
C--------D------E
   10       10

A, B, D are VA routers. A is APR. B and E are legacy routers capable of 
only hop-by-hop forwarding, i.e. not doing MPLS. Link metrics are shown.

Packets ingress the topology at A. They get forwarded to B as plain IP 
since B is not an LSR. B forwards plain IP packets to D. D is a VA 
router and has suppressed the specific routes, thus it sends the packets 
back to A.

--
dg
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