Subject: Re: CR-LDP and RSVP implementation

From: David Charlap <[email-masked]>
Date: Tue, 20 Feb 2001 17:29:03 -0500

>> - RSVP-TE uses a different QoS representation from CR-LDP
> 
> Most of the objects associated with QoS in CR-LDP were lifted
> bodily from RSVP-TE and the resemblence is striking.

They both use the concept of a token bucket.  But the number of buckets
and their use is different.

>> - RSVP-TE explicltly LSPs from a known ingress router to a known
>>   egress router.  LDP distributes labels without a firm concept of
>>   an LSP during the signalling.  CR-LDP appears to be like LDP in
>>   this respect, although the presence of an explicit route mitigates
>>   the difference somewhat.
> 
> CR-LDP includes Explicit Routing using mechanisms and objects
> that are very nearly identical to the objects included in RSVP-TE
> (this time, both efforts "borrowed" from the same bank).

But CR-LDP doesn't have a concept of a tunnel endpoint address.  One can
be derived from the ERO, but the ERO is not necessarily present.

>> - There is no LDP or CR-LDP way to signal multiple LSPs that share
>>   resources.  (RSVP's "SE" reservation style)
> 
> CR-LDP accomplishes this using LSP-ID.

I don't see this explicitly documented anywhere.

The closest thing I see is the Action Indicator Flag, and it says
nothing about reservation styles.  It specifies whether the LSP being
signalled is a new LSP or a modification.

There is still no way to signal two separate LSPs that share resources. 
This can be for reasons other than a make-before-break operation.  (For
example, one could be a standby LSP waiting for a failover.)

-- David