The MPLS WG Archive

[David Charlap <david.charlap@marconi.com>]

"Thomas D. Nadeau" wrote:
>> 
>> Set to zero (or some other NetAdmin controlled
>> value) extended tunnel id allows sharing between LSPs provided their
>> Session id is the same.
> 
> That is not a MIB issue. If the admin does what you describe,
> then RSVP will not work, period. You will have mis-configured
> your network because you will have non-unique sessions, and thus
> sessions will not be signaled.

No.  This is not at all true.  There is _NOTHING_ in RSVP that requires
every LSP to be in a separate session.  Multiple LSPs sharing a single
session is the mechanism by which resources are shared.  It is this
precise mechanism that allows make-before-break to work.

Setting the extended tunnel ID to zero is perfectly legal.  It is the
mechanism by which multiple LSPs may share resources if they originate
from different routers.

> This is not a MIB issue.  I think that the BCP here is to do what
> the RSVP-TE specification suggests (and should have made mandatory,
> IMHO). That is, to set the ingress LSR id as the extended id.

I would strongly disagree with you here.  RSVP-TE has this mechanism,
which makes it relatively simple to support many-to-one LSPs.  Would you
rather someone creates a new, and incompatible mechansim for this
instead?

It is well known that the MIB does not support all of the features of
RSVP-TE.  This discussion has gone around this group several times.  It
is clear that the authors of the MIB are not interested in being able to
represent every kind of setup that RSVP can legally get into.  That's
their choice, of course, but it doesn't mean that RSVP's specification
should now be changed in order to accomodate it.

That's like wanting to redesign a car for a top speed of 85, because the
speedometer doesn't go any higher.

-- David