Re: [nsp] MPLS Traffic engineering

From: Eric Osborne (eosborne@cisco.com)
Date: Mon Nov 06 2000 - 08:56:26 EST


On Mon, Nov 06, 2000 at 11:29:46AM +0000, Neil J. McRae wrote:
> > Hi All,
> >
> > Thanks a lot once again for all the advice I have recieved. In the
> > mentioned versions of IOS, Can the OSPF support for Traffic enginnering be
> > extended to multiple OSPF areas, Because I was reading one of the Cisco
> > docs which was stating that the current OSPF support for TE is only for a
> > single area ie area 0.
>
> I believe this is true because of sumarisation issues between areas.
> [Although it would make my day if this wasn't the case].

Well, it's true, but not because of summarization. Not sure if that
makes you happy, or sad. :)

MPLS-TE relies on information distributed by your IGP - in the case of
OSPF, Type 10 Opaque LSAs. Type 10s are area-local, so we don't have
enough information about what's in other areas to do LSP path
determination at the head-end. Inter-area is a tricky problem to
solve, because the simple solution (flooding the entire network
topology) isn't scalable, and kinda obviates areas in the first
place. IS-IS has the same problem, but IS-IS networks tend to be a
single much larger level, rather than several small areas like OSPF has.

There's some ietf work to standardize multi-area TE; check your
favorite ietf drafts archive. cisco is working on something too, but
seeing as I'm neither marketing nor development, I can get away with
saying "It's coming". :)

eric



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