The MPLS WG Archive

[Yangguang Xu <xuyg@lucent.com>]

> 
> > A virtual link is between an ingress node and an egress node (not adjacent
> > in most of the cases). Intermediate nodes don't see the signaling messages
> > when you want to provision a circuit (LSP) inside that virtual link. The
> > label allocated for a VC-12 in that virtual link is ONLY relevant to the
> > ingress and egress nodes. It is NOT seen by the intermediate nodes. The
> > virtual link bandwidth is in that case VC-4 and the label for a VC-12 in
> > that VC-4 don't care about the number of the STM-x. The virtual link may
> > span several physical links. A virtual link is an LSP and can be advertised
> > as a Forwarding Adjacency (please, read the corresponding drafts).
> >
> 
> I think intermediate nodes need to see the signaling messages when provision a
> lower order LSP. In this case, higher order LSPs will be treated as FAs or
> tunnels. Explicit routing calculates the lower order LSP and puts higher order
> LSPIDs in ERO. Labels then indicate which low order time slot within the higher
> order LSPID.
> 

Eric,

Correction on my comment, if intermediate node only support high order
switching, then you are right that only end points need to be involved. (It's
like ATM VP switching). If intermediate nodes also support low order switching
(like ATM VC switching), then they need to be involved for low order LSP
creation.

Regards,

Yangguang