[Nml-wg] About modelisation of the network description

[Evangelos Chaniotakis]

Freek Dijkstra wrote:
> Evangelos wrote about the "Model" object:
>
>> Can we call them "Views" instead of "Models"? "Model" is a quite 
>> overloaded
>> word, especially in a semantic context.
>>
>> But otherwise, thanks for writing this up. This is really close to 
>> work currently under development in the IDC project.
>
> Currently, I see two concepts here: an (administrative) network 
> domain, and a filtered view. The relational difference is that a 
> device can only be part of ONE "domain", but part of MULTIPLE "views".
>
Agreed.

> Evangelos, does that mean you like to have both a "domain" object
> for grouping, and another "view" object that gives you a filtered view 
> of the contents of this group? Or do you only want one "View" object 
> that is just some grouping of network elements?
A "view" can be more than a simple grouping or filtering; it could be
a complete restructuring of the network elements. The most common
use case in the control plane world would be reducing a network to a
simpler topology, and possibly obfuscating device and interface names,
to safely provide the data to an untrusted party.

In general, a domain might offer different views of its topology with
varying complexity and parameters, each targeted to a different
class of applications. I think that's what Aurelin is shooting for,
and I think it's a great idea.

Anyway, here's what I think that sort of structure would look like:

- Domain
--- View (type = "monitoring")
------ Network Element
------ Network Element
-------- Network Element
------ ....
--- View (type = "controlplane")
------ Network Element
------ Network Element
------ ....
--- View (type = "export")
------ Network Element
-------- Network Element
------ Network Element
------ ....

and so on and so forth.

>
> Do we need a third "network" concept for grouping, besides (or instead 
> of) "domain" and "view"? If so, what would be the relation between 
> devices and such "network" and how is that different from "domain" or 
> "view"?
I'm on the fence as to whether we need a separate "network" concept. We 
might
need to model administrative domains that run multiple independent 
networks.
Examples: the GEANT testbed network vs the GEANT production network, or
ESnet Science Data Network vs ESNet IP core vs ESnet optical testbed. 
Devices
may belong to multiple of these "networks", too.

I kindof think that each of these may be safely modeled as an 
administrative domain
of its own, but that breaks the device->single domain relation. Or, we 
can describe
each with its own View, which makes for a simpler schema but may not be
100% semantically correct. Any feedback is appreciated.





> Did the IDC project made such choices already?
>
> (My opinion: I like to see at least an (admin)domain object, and 
> possibly a "view" object. I don't yet see a need for a "network" 
> object different from a "domain" object. Nevertheless, Aaron presented 
> exactly those two, and I love to hear that argument).
>
We haven't made hard choices per se. We're working on automatically
"abstracting" network topologies for export. The abstracted view of the
topology needs to be made persistent.. so we came up with a  database
construct similar to the above.