Subject: RE: FW: [Isis-wg] draft-ietf-isis-traffic-01.txt

From: "Radulescu-Banu, Cristina" <[email-masked]>
Date: Wed, 6 Oct 1999 08:51:03 -0400

>That said, the topology information that one extracts out of the TE
>information can be used independently of any area or level boundaries.  It
>is simply a graph or 'map' if you like.

Thank you all for your answers.
I guess I was confused by the extended IP reachability TLV, which I thought
changed to carry also some TE attributes (maybe to avoid confusion, this
extended TLV shouldn't be in the TE draft, since the changes are just for
redistribution in between levels/areas - kind of summarization between areas
for Ospf-). After a careful reading ;-), yes, the TE topology is "area"
bounded (by that I mean that a set of routers in a given area only see a TE
topology (synonym "graph, or "map" ;-) only inside the area,  although they
have non-TE reachability to networks( and routers ) in other areas.

Thanks again,
Cristina 

Cristina Radulescu-Banu
Redstone Communications, Inc.
5 Carlisle Road
Westford, MA 01886

[email-masked]
(978) 692 1999 x147
(978) 692 9992 fax

-----Original Message-----
From: Tony Li [mailto:[email-masked]]
Sent: Tuesday, October 05, 1999 5:10 PM
To: [email-masked]
Cc: [email-masked]; [email-masked]
Subject: Re: FW: [Isis-wg] draft-ietf-isis-traffic-01.txt

Cristina,

I think we first need to be _very_ careful about what you mean by
"scoping".  

IS-IS TLVs by their very nature are not automatically exchanged between
areas or between levels.  This is no different for TE information and the
draft need not say anything specific about this.

The TLVs were not designed to carry topological information independent of
the LSP that they exist in, so their use in other areas or levels would be
non-trivial.  This was definitely not the intent.

That said, the topology information that one extracts out of the TE
information can be used independently of any area or level boundaries.  It
is simply a graph or 'map' if you like.

One possible application of this is to do multi-level traffic engineering.
Suppose that you had IS-IS areas interconnected using an OSPF (or IS-IS
level 2) backbone.  A traffic engineering path could compute a strict route
across one IS-IS area.  Then the boundary router between the protocols
would compute a strict path across the backbone, and the exit boundary
router would compute a strict path across the exit area.

Other wierd and wonderful things are also possible.  The spec is written
specifically to minimize future limitations while providing the
functionality that we want today.

Tony

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