IETF CCAMP Respons to OIF on Inter-Level Routing

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

Dear Lyndon,

Here is a final response to the issues raised by the OIF. This one relates 
to ASON routing and multi-layer networks, and comes from your communication 
oif2008.063.02.pdf.

> in our discussions of multilayer networks and impacts on the control 
> plane, we took note of ITU-T Recommendation
> G.7715.1 requirements to advertise:
> a) Local Connection Type; and
> b) Local Client Adaptations Supported.
> We believe that this functionality would be very useful for
> applications that have been discussed in OIF (see
> attachment). We would appreciate further clarification as to
> whether both requirements have been addressed in the current
> CCAMP work on ASON routing support (local connection type in
> particular is not explicitly identified in the current draft). We would 
> also appreciate more information on the
> relationship between support of adaptation in the ASON routing draft and 
> in the multilayer/multiregion networking
> drafts also being developed in the CCAMP WG.

We note that G.7715.1 discusses the operation of multi-layer networks in an 
appendix and observes:

  This appendix provides illustrative examples of different
  methods of carrying multiple layer information between two
  systems. It does not mandate a particular method of
  implementation for link state routing protocols.

  From the perspective of ITU-T Rec. G.8080/Y.1304, each layer
  network has its own instance of a control plane.

It can also be observed that a single routing level cannot span multiple 
network layers within the ASON architecture.

draft-ietf-ccamp-gmpls-ason-routing-ospf-06.txt addresses the distribution 
of routing information between Routing Areas (in the ASON sense), but is 
agnostic to the routing information passed. For more details of the exchange 
of "local connection type" and "local client adaptations" we need to look 
into the base GMPLS routing specifications and the CCAMP work on multi-layer 
networks.

As pointed out in RFC 4652, the Switching Capability field of the Interface 
Switching Capability Descriptor (see RFC 4202) describes the capabilities of 
the receiver with regard to any specific TE link (e.g., PSC, TDM, etc.).

Your question also opens up the issue of distinguishing between what signal 
types an LSR can terminate (through adaptation) as distinct from switch 
(onto another TE link). This function is addressed in another CCAMP draft, 
draft-ietf-ccamp-gmpls-mln-extensions-03.txt, which will go to CCAMP working 
group last call soon. This draft introduces the Interface Adaptation 
Capability Descriptor (IACD) to carry the necessary information.

Both the ISCD and the IACD can be exchanged between routing levels using the 
techniques described in draft-ietf-ccamp-gmpls-ason-routing-ospf-06.txt. You 
may, however, also like to look at the appropriateness of the PCE 
architecture (RFC 4655) in the role of inter-level routing as it seems to 
fit well with the architecture as described by the ITU-T in G.7715.2.

Best regards,
Adrian Farrel and Deborah Brungard
IETF CCAMP Working Group Co-Chairs