[Nml-wg] Adaptations

[Freek Dijkstra]

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.

Regards,
Freek