Subject: [rbridge] Wide Metric TLV and SPF

From: "Ramalingam, Swaminathan (Swami)" <[email-masked]>
Date: Wed, 9 Sep 2009 12:16:36 +0530

TRILL mandates to use wide metric TLV (RFC 5305) and not to use TLV
type 2 (traditional metric). Distribution tree calculation talks about
only cost based tree calculation (i.e. just metric based). I assume
this is just to use wide range of metric value or is there any plan
that TRILL can use CSPF based path calculation (I don't see any
mentioning of this in the draft version 13). It probably make sense if
TRILL can use TE capability (parameters) to do the path calculation,
optionally. Also I don't see any mentioning of sub-TLV usage for TRILL
purpose.

-Swami
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From: Donald Eastlake <[email-masked]>
Date: Wed, 9 Sep 2009 10:19:55 -0400

Hi,

> mentioning of this in the draft version 13). It probably make sense if

This may be due to the attention paid in TRILL design to zero
configuration operation. Any Constrained Shortest Path First  (which I
assume is what you mean by CSPF) path calculations based on some
policy would require the use of that policy at all RBridges of
interest (possibly all RBridges in the campus) to avoid loops. Some
policies could also result in partition from the point of view of
traffic transmission. I don't see anything in the draft prohibiting
use of such policy.

> optionally. Also I don't see any mentioning of sub-TLV usage for TRILL

"sub-TLVs" are mentioned in several places in the draft. If you are
talking about sub-TLVs associated with adjacencies in the IS Extended
Reachability TLV, that seems like the only reasonable place to put the
tested MTU for an adjacency and the like, as mentioned in Section 4.3.
As discussed on this list, that will probably be added to item 1 in
Section 4.2.4.4 in the next version of the draft. I don't think there
is anything in the draft prohibiting other sub-TLVs.

> -Swami

Thanks,
Donald