[Nml-wg] [Nsi-wg] Conversation about ITU concepts with Ciena folks
Guy.Roberts at dante.net
Fri Sep 4 04:43:25 CDT 2009
I note a couple of interesting (and to me) new points from the documents provided by George Newsome. As I see it, there are broadly two ways of approaching pathfinding in multi-domain, multi-layer networks:
Approach 1: AutoBAHN like - the layers are collapsed into a single abstracted layer and pathfinding is done on this layer. We then perform stitching on a set of possible paths.
Approach 2: path finding is done on a complete multi-layer graph with full knowledge of layer adaptations. A much more limited (if any) stitching function is then required. I think this is more like the method proposed by Freek in his thesis.
The multi-layer pathfinding proposal included in the documents from George Newsome is interesting, and in my view is close to the method used by AutoBAHN, namely the topology is fattened into a single layer which assumes the presence of adaptation in each node. Pathfinding is the done on this flattened topology. The problem not addressed by George Newsome is the issues covered in Victor Reijs's stitching work.
The other document of note is the transitional link document. I think we need to be careful about adopting this concept since as far as I can see it has been created by ITU-T for a very specific purpose. They use it for transit between sub-layers as opposed to adaptation between layers. In their example a transitional link is used for all-optical conversion of wavelengths, where wavelengths are not real layers as there is no termination and adaptation function
when converting between wavelengths.
From: John Vollbrecht [mailto:jrv at internet2.edu]
Sent: 02 September 2009 21:53
To: NSI WG
Cc: Network Markup Language Working Group; Rajender Razdan; Lyndon Ong; George Newsome; Jeff Verrant; Daniel Getachew
Subject: [Nsi-wg] Conversation about ITU concepts with Ciena folks
Jeroen van der Ham, Guy Roberts and myself had a conversation with Lyndon Ong, George Newsome and Rajender Razdan of Ciena about ITU networking recommendations. This was extremely helpful, and I thank the Ciena folks very much for their time and help.
The following notes are put together by Jeroen and myself - please feel free to add or correct or question.
We spend the first part of the meeting going over slides (see attachnment below) describing NSI concepts in G.800 terms. It is worth noting that George described the evolution of the recommendations as G.805 describing connection oriented networks, G.
809 attempting to extent that to connectionless networks, and then G.
800 which combines both. He also commented that the way that G.800 came to be is that "G.805 was observed to be insufficient for describing packet-switched networks (especially ethernet). Updating a
standard is hard, hence a new standard." So using G.800 concepts is
what is done in the slides and in discussions we have had earlier on the mailing list.
G.8080 unfortunately still uses G.805 terminology, and adds some more
- but is in the process of being updated/reviewed. G.8080 is also called ASON.
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