[Nsi-wg] NML topology

[Guy Roberts]

Hello all,

I my opinion one of the main problems that has held up progress in the NSI working group has been our failure to agree on a clear set of NSI requirements for network modelling.  I think we have agreed that these should be a minimal set of extensions to the existing NML model, so this should not be a very large set of requirements.

What has happen is that many alternative proposals for network models have been suggested, without first clearly identifying and agreeing a set of requirements.  I think this has been back-to-front, first we should identify the requirements, and then a group of modelling experts should come up with a proposal for NML extensions.  

So with this new approach in mind, I would like to kick of a discussion on what the essential requirements NSI has for network modelling.  These should only include requirements that go beyond the functions that are already supported in the current NML definition. 

I suggest the following 10 requirements as a starter:

Requirement 1: The model should be able to describe a grouping of network resources that are owned and controlled by a single provider or NSA. (I will call this a NETWORK for the moment)
Requirement 2: The model should be able to describe a grouping of NETWORKs. (e.g. a federation of providers with shared policy)
Requirement 3: The model should be able to describe resources (ports/points) in a NETWORK that are available for connecting to other NETWORKs.  (I will call this a network connection point NCP for the moment)
Requirement 4: These NPs should be able to be performed at the end of a link that is internal to the domain as well as to ports on a device.  (in my opinion the NCP on a link requirement needs a use-case)
Requirement 5: The model should be able to describe an arbitrary number of layers of logical ports within a NCP.
Requirement 6: The model should be able to describe connectivity between NETWORKs. (I will call this inter network connection (INCs) for the moment) 
Requirement 7: The model should be able to describe groups of INCs.
Requirement 8: The resources that make up INCs should have ownership by a clearly identifiable provider. (i.e. resources without NSA ownership are not allowed).  (note: Does this also include the patch cord between providers?)
Requirement 9: The model should allow policy to be assigned to INCs, even where the INC is wholly or partly made up of passive resources.
Requirement 10: The model should be able to fully describe a circuit (i.e. NSI service) that transits the topology. 

Any thoughts on these and other requirements would be helpful.

Guy


-----Original Message-----
From: Freek Dijkstra [mailto:Freek.Dijkstra at sara.nl] 
Sent: 22 February 2010 13:52
To: NSI WG
Cc: Guy Roberts; Jeroen van der Ham; John Vollbrecht
Subject: Re: [Nsi-wg] NML topology

Can I summarize this discussion as follows?

Requirement: It should be possible to assign a policy to an
(interdomain) link.

Of course, I can think of a solution (e.g. make that link part of a
topology, like John's second picture, assign the topology to a
networkdomain, and assign a policy to that networkdomain). However, this
seems out of scope. I think the best way forward is to describe this and
other requirements and forward them to the NML and ask the NML folks to
come up with a solution for the requirement. I also wholeheartedly
invite all NSI group members to become a "NML folk" too by joining the
NML list!

Regards,
Freek