[Nml-wg] Services

[Freek Dijkstra]

We had a longer discussion if NML should define services?

It was quickly clear to us that there are clearly two interpretations of
the word "service":
1. Service as a network transport function. For example, an adaptation
and network connection are transport processing functions. In the ITU, a
lower layer is called a service layer which provide a network function
to a (higher) client layer.
2. Service as a control plane daemon. For example a topology exchange
service or a provisioning service.

Regarding a control plane service:
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Should NML define services?
No, but we should facilitate the tying of a service to the network
description

Template for generic service.
We should look at OGSA. GLUE.
Evangelos volunteers to propose a template definition.

Guak: service may operate on a network


Regarding a data transport function:
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Martin argued that Adaptation is just a subclass of Service.

I gave his idea some thought over the weekend, and it seems to me that
the high level proposal is to define a "service" as a dynamic transport
function. That could both imply a cross connect as well as a dynamic
adaptation.

While I am now convinced that this high level idea is good (good
suggestion, Martin!), I do not know how to make this into the schema
yet. I am not convinced that Martin's schema proposal (made Adaptation a
subclass of Service) is the right way forward.

Mostly, I think Service is about *dynamic* (thus changable) trasport
functions. A service is thus mostly about describing a *capability* ("it
is possible to make this cross connect or this adaptation") and not
about the *configuration* ("this-and-that adaptation is currently in
place").

NDL only defined cross connects as part of the switching matrix (which
contained information about capabilities). However, it did define
adaptations, even dynamic adaptations outside of the switch matrix.
I am very interested to hear about schemas that did this differently.

Here are 3 different adaptations:
* Fixed wavelenght over a fibre. This is what happens in most GBICs, and
we should be able to describe this as a static feature -- devices often
have no knowledge about the characteristics of the GBIC (e.g. is it 50
or 100 GHz spacing?)
* Configurable wavelenght over a fibre. This is what happens in a
tunable laser. The adaptation remains in place, but some of its
properties (here: the label) changes.
* VLAN channel over an Ethernet interface. This is a completely dynamic
adaptation, which may completely be removed in software (if the Ethernet
interface is switched from tagged to untagged).

Should all these be represented with the same schema (database entries),
or should we distinguish between static and dynamic adaptations. If so, how?


Regards,
Freek Dijkstra