[Nml-wg] Adaptations

[John Vollbrecht]

On Jun 25, 2008, at 11:21 AM, Freek Dijkstra wrote:

> John Vollbrecht wrote:
>
>>>> For example, and OTN port might  convert things to SONET,  
>>>> Ethernet, and other line protocols.  Is this  adaptation?
>>>
>>> Yes, if "things" is a higher layer than SONET or Ethernet.
>> I think that I  understand what you are saying - that  a link has  
>> a single stream on it and that single stream can be adapted to  
>> some other layer.  However, in multiplexed networks like  DCN a  
>> link can carry many streams and each stream can be adapted  
>> differently.  In fact, in an ete circuit there may be several  
>> links and each link may do a different adaptation.   How does the  
>> topology describe something like this?
>
> Good question.
>
> If we talk about a "link" we actually mean a logical link, or a  
> channel (G.805 talks about "a transport entity across a link").
>
> Thus a fiber with different wavelenghts would be described as a  
> link at the fiber layer, and multiple links at the WDM layer.
>
> Either only the fiber link is in the database, and the other links  
> are "derived" from the combination of adaptation, link and de- 
> adaptation, or they are all present in the database.
>
> The relation between these links would be an adaptation relation  
> between the ports on each layer. In this particular case, the  
> relation would be a multiplexing adaptation function, which is an  
> adaptation with multiple channels on the higher layer and one on  
> the lower layer.
>
> Each port on the WDM layer has a "client" relation with the  
> adaptation instance. The (single) port on the fiber layer has a  
> "server" relation with the adaptation instance.
>
> It is possible that the WDM layer ports could in turn have "server"  
> relation with other adaptation instance, each different. Perhaps  
> wavelength 1 carries multiple STS timeslots, while wavelength  
> carriers Ethernet.
>
> Let me know if you like me express this example in instances of  
> classes in the current NML schema.

before expressing this perhaps a little more exploration of the  
concepts.

 From what you say, I assume that a logical link between two ports  
would be what in DCN I call a path segment.  A path  segment has uses  
some resource on a physical link.  in this case, each logical link  
then can have an adaptation.  This is ok - but --

where is a physical link described?  how do I know how a physical  
link can be subdivided into dynamic logical links?  how do I create  
an ete circuit that is a concatenation of logical links.  How do I  
name the ete circuit and treat it as an entity that is time variant?

These are what seems to me to be needed for DCN, to both create  
reservations and circuits, and to monitor the reservations and circuits.

John

>
> Regards,
> Freek

John Vollbrecht, Senior Network Engineer
Internet2
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