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

From: "Radulescu-Banu, Cristina" <[email-masked]>
Date: Tue, 5 Oct 1999 11:59:21 -0400

I, God forbidden, don't want to run 2 IGPs at the same time; however, the
IsIs TE spec says: "If Ospf is also active in the domain, TE can compute the
mapping between OSPF and IsIs topologies" (domain == AS)

So, if you can, they have to have the same TE scope (one area). Even if you
run only one IGP at the time, you still want to have the same definition for
TE topology boundaries.

I didn't see any mention in the ISIS TE spec that it is area scoped, so I
just wanted to make sure I really just missed it.  I also saw mentions of
prefixes being redistributed from/into areas, i.e.:
"If a prefix is redistributed from an area to another area at the same
level, then the up/down bit shall be set to 1." in 4.0, The extended IP
reachability TLV- .
So, I guess I'm still confused if the TE topogy is area bounded or not. Can
you clarify (again  ;-) that TE info doesn't get summarized from an area
into another?

Thanks again, (sorry if this was a clear issue for everybody else),
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: Henk Smit [mailto:[email-masked]]
Sent: Tuesday, October 05, 1999 11:28 AM
To: [email-masked]
Cc: [email-masked]
Subject: Re: FW: [Isis-wg] draft-ietf-isis-traffic-01.txt

  Why do you want to run OSPF and ISIS on the same topology ?
 Isn't one IGP enough ?
  I might be mistaken here, but AFAIK both ISIS and OSPF TE extensions
 are only defined within one area.

      Henk.

> I have a question about IsIs/Ospf traffic engineering drafts; Ospf and
Isis
> TE drafts are pretty similar, however, the OSPF TE domain is area scoped;
> (the TE info from an area is not summarized in other areas).
> I didn't see any similar constraint in the IsIs draft; how can you map
Ospf
> and Isis TE topologies if you have a much bigger Is-Is TE topology than
the
> Ospf TE topology (this last one ends at area boundaries)? 
> Thanks in advance,
> Cristina

_______________________________________________
Isis-wg mailing list  -  [email-masked]
http://external.juniper.net/mailman/listinfo/isis-wg

---

From: Tony Li <[email-masked]>
Date: Tue, 5 Oct 1999 14:09:51 -0700

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