The MPLS WG Archive

[Eric Gray <eric.gray@sandburst.com>]

David,

    Hmmm.  There is the interworking scenario:

  --- R1 --- R2 --- R3 ---

in which R1 only "speaks" CR-LDP/LDP and R3 only
speaks RSVP-TE (and maybe LDP).  In this scenario,
it is quite reasonable for R2 to "translate" between the
two protocols for LSP set-up.

    Also, there is very little difference between setting
up a single LSP through (for example) R2 above and
terminating one LSP (from R1, for instance), making
a new LSP (toward R3) and connecting them internally
(at R2) - as long as the mapping (might be a FEC) is
one-to-one from one LSP to the other.

--
Eric Gray

You wrote:

> djiang1@lucent.com wrote:
> >
> > I have a question regarding CR-LDP and RSVP implementation.
> >
> > I guess it is possible that both CR-LDP and RSVP implementations will
> > be supported on one LSR.
>
> Definitely possible.  And quite probable in the future.
>
> > However, is there any chance that both the implementations will be
> > called for one LSP setup?  Say, at the incoming interface, CR-LDP will
> > take the PATH message and pass it to some other MPLS processes.  At
> > the out going interface, RSVP will get some message from other MPLS
> > processes and does something in the middle and sends out another PATH
> > message to its neighbor node.
>
> I don't think so.
>
> The only way I can picture such a setup would require a transit router's
> ability to terminate one LSP, then initiate setup of another, and
> connect them internally.  Theoretically possible, but difficult to
> automate and of questionable utility.
>
> I think you may find MPLS networks where RSVP-TE, LDP and CR-LDP are all
> used for LSP setup at once.  And this may well result in multiple
> redundant LSPs between edge nodes.  But each individual LSP will almost
> certainly be set up through exactly one protocol.
>
> -- David