Re: Signaling client layer LSP over VCAT server layer LSP

["Adrian Farrel" <adrian@olddog.co.uk>]

Hi,

IMHO the two drafts are not so closely related.

Hierarchy bis describes how, when an LSP is set up, the ingress may indicate 
to the egress that the LSP is to be advertised or used as a link in some 
specific network layer.

LSPs set up for VCAT are not used in that way. They are grouped together and 
the whole group is used as a link in another network layer.

So, for VCAT, one might use the call as the mechanism to exchange 
information about how to use the entire VCG as a link in the client layer. 
Alternatively (if one is implementing strictly according to the 
architecture) one might have three layers to consider...

- The server layer where a call coordinates multiple TDM LSPs
- The VCAT layer where a single hop LSP is requested between
  VCG end points resulting in the server layer call. The VCAT
  layer LSP would use hierarchy bis to determine that it should
  be advertised as a TE link in the client layer.
- The client layer where a magic TE link appears as the result of
  the VCAT layer LSP.

Depending on the deployment, the use of a VCAT layer LSP might be considered 
to be over-engineering. Just because an architecture defines multiple 
layers, it does not mean you have to implement them explicitly. It might be 
enough for the server layer call to provide the coordination with the client 
layer direct.

Cheers,
Adrian
----- Original Message ----- 
From: "Bardalai, Snigdho" <Snigdho.Bardalai@us.fujitsu.com>
To: "Kohei Shiomoto (E-mail)" <shiomoto.kohei@lab.ntt.co.jp>; "Greg 
Bernstein (E-mail)" <gregb@grotto-networking.com>
Cc: "Ccamp (E-mail)" <ccamp@ops.ietf.org>; "Adrian Farrel (E-mail)" 
<adrian@olddog.co.uk>
Sent: Saturday, March 15, 2008 7:25 PM
Subject: Signaling client layer LSP over VCAT server layer LSP


Hello Kohei and Greg,

I have a question about client layer LSP signaling (e.g. ethernet) over VCAT 
server layer resources.

From reading 'draft-ietf-ccamp-lsp-hierarchy-bis-03.txt' it is not clear how 
will this exactly work.

For example, we set up a VCAT group (i.e. by signaling multiple STS1 LSPs) 
as allowed by the VCAT ID. I believe each of these LSPs would appear as 
LSP_TUNNEL_INTERFACEs in the client layer with bandwidth capacity equivalent 
to STS1 (i.e. 52mbps). My question is which LSP_TUNNEL_INTERFACE will be 
used for signaling the ethernet LSP, I think an additional component link 
with bandwidth capacity equivalent to the aggregate bandwidth will have to 
be created.

Is there a defined way of handling this situation?

Thanks,
Snigdho