[Nsi-wg] NML topology

[Guy Roberts]

Jeroen,

If we put aside the question of point vs port naming for the moment,  I think that John's slides raise an important question.  This is how best to describe connectivity between networks.

One option is to carry over the exiting NML concepts and assign a link as the connection between two networks.  In this case the link will have to be 'un-owned'  i.e. it is not within the control or ownership of either network.

The alternative option presented by John is to use a port or point concept to joint two ports on adjacent networks.  In this case there are no objects (i.e links) between networks - this solves the problem of un-owned resources.

To understand the implications of the existing NML model better, lets take the example of a fibre that connects two Ethernet switches in adjacent racks.  In this case I expect that the NML model will nominate the two Ethernet ports on the switches as 'Ports' and the fibre as a 'Link'. In this example it might be possible to replace the fibre with a transatlantic wavelength leased by one of the end networks. The question in my mind is how we allocate ownership of the inter-domain 'link'.

If we follow John's model and insist that there are no resources that are 'un-owned', then we need to allow the modelling of connectors that do not belong to switches.  So going back to my previous example, the demarcation point between networks moves from the Ethernet ports on the switches to a connector on a distribution frame that marks the boundary of physical ownership between the two networks.  In other words the schema would model the demarcation point between networks in a much more literal physical way.

The question in my mind is whether there is a real use-case for the second model.  Does NSI need to model the demarcation of ownership of items in the inter-network space, eg wavelengths or patch chords between providers?  This is a interesting question and needs a very clearly documented use-case.  


Guy

-----Original Message-----
From: Jeroen van der Ham [mailto:vdham at uva.nl] 
Sent: 21 February 2010 21:08
To: John Vollbrecht
Cc: NSI WG
Subject: Re: [Nsi-wg] NML topology

On 21/02/2010 18:20, John Vollbrecht wrote:
> Attached is set of ppt slides to describe interdomain topology.  I
> hope this helps - it is based on conversations in the NML group, and
> is my understanding of what the Glossary of terms that Guy is
> reviewing (and I think will review next Wed).

I just want to clarify my view of the conversation we have had in the 
NML group about this issue. This was mainly a discussion between myself 
and John wherein I tried to understand the NSI issue of describing 
inter-domain topologies.

The current NML topology model does not have "Points". Nor do we 
currently have plans to add them. *Unless* there is a use-case showing 
the need of Points, which clearly outlines why it is not possible to 
describe domain boundaries with the current NML Topology model. So far, 
I have not seen such a clear and valid use-case for "Points".

Jeroen.
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