[Nml-wg] Use case: a media converter (multi-layer)

[John Vollbrecht]

Freek -

I have some questions about the
On Aug 10, 2009, at 1:15 PM, Freek Dijkstra wrote:

> Hi,
>
.
.
.
>
> Finally, I have not explicitly defined the layer for each interface,
> because it was already apparent from the (de)adaptations. For a single
> layer Node, this information can not be derived (is not transitive).  
> So
> there is may be necessary to make this explicit.
>
.
.
.
> This defines a new attribute, atLayer, which might be defined as a
> Relation type if the Layer class is a subclass of Network Object.
>

I am not clear on the definition of a layer.  Is everything that has a  
different characteristic information a different layer?  I have been  
thinking that a layer was where technologies differed in a way that  
the user information could not be multiplexed directly on links from   
one layer to another.  For example, ethernet would be a single layer,  
where segments at the layer carry ethernet coded with different  
characteristic information.

SONET could carry ethernet segments by encoding them using GFP.   
However once GFP encoding is done then the segments at the  SONET  
layer are carried in VCGs or sets of channels.  ethernet frames (coded  
in GFP) can be carried with other segments, and the layer (in my view)  
supports SONET links which carry STS1 channels, while the ethernet  
layer supports Ethernet links which carry VLANs.

In some ways these are similar concepts, but the concept of being able  
to create and concatenate segments of a particular client type seems  
to me to be the important concept for dynamic connection concepts of  
NSI.   What is your view?

John
> Regards,
> Freek
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