[Nsi-wg] [Nml-wg] Conversation about ITU concepts with Ciena folks

[Jeroen van der Ham]

Hello,

I agree that George's multi-layer pathfinding seems very similar to the
 AutoBAHN approach.

Freek in his thesis argues that this approach can work, but does not
have a way to handle incompatibilities. Freek uses an example where
there are two ways to map Ethernet onto SONET, and the source and
destination use different mappings.
A path through the network will have to do a remapping along the way,
otherwise it can't work.

I do not see how a collapsed topology can ever solve such a problem.
Perhaps it can, but it will have to specifically supported by the
stitching framework.

Jeroen.

Guy Roberts wrote:
> Hi John,
> 
> 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.
> 
> Guy
> 
> 
> -----Original Message----- 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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