[Nml-wg] Adaptation in GMPLS

[Freek Dijkstra]

Jeroen van der Ham wrote:

> [...] we use [a] different model [than GMPLS].

You dismiss the GMPLS approach rather quickly. To play the devil's 
advocate: the GMPLS group was the first to point me to G.800, which we 
now triumph so much. So their model is not that different.

Surely you are referring to the fact that GMPLS does define the line 
encoding ("LSP Encoding Type") -the layer of the link in NDL- and 
"Switching Types" -the layer of the switch matrix in NDL-, but does not 
describe HOW that data may be adapted from one to the other layer.

You are right though that originally, GMPLS did not describe adaptations 
explicitly (since they never assumed incompatibilities there). However, 
they certainly did consider this. A draft of RFC 5339 said:

> the advertisement of the internal adaptation capability of hybrid
> nodes is required.

I just discovered that in the final RFC this has changed to:

> The advertisement of the adjustment capacities is required, as
> it provides critical information when performing multi-region path
> computation.

Where "adjustment capacities" is defined as:

> The term "adjustment capacity" refers to the property of a hybrid
> node to interconnect different switching capabilities it provides
> through its external interfaces [RFC5212].  This information allows
> path computation to select an end-to-end multi-region path that
> includes links of different switching capabilities that are joined by
> LSRs that can adapt the signal between the links. 

They are trying to add the adaptation information to GMPLS.

See also:

RFC 5212: Requirements for GMPLS-Based Multi-Region and Multi-Layer 
Networks (MRN/MLN)

Generalized Multi-Protocol Label Switching (GMPLS) Protocol Extensions 
for Multi-Layer and Multi-Region Networks (MLN/MRN)
http://tools.ietf.org/html/draft-ietf-ccamp-gmpls-mln-extensions
(the last one is fresh -- it was updated 3 days ago).

Regards,
Freek