[Nml-wg] Questions

[Freek Dijkstra]

On 18-12-2013 17:54, John MacAuley wrote:

> Not sure if these are NSI specific questions, or general NML
> questions.  All relate to Port/PortGroups and use of labels.
> 
> 1. I can have a Port without a Label, and a PortGroup without a
> LabelGroup.  In this case the Port id alone uniquely identifies the
> resource.

Yes.

> 2. Can i have a Label or LabelGroup specified with a label type but
> no value?  In this case the Port is identified uniquely by id and
> label type.

I think that the syntax allows a label type without label value. Out of
curiousity, what's the use case? I can't think of an example.

What do you mean with "the Port is identified uniquely by id and label
type". Do you mean the Port id or the Portgroup id? I presume that a
Port is identified uniquely by it's Port id.

> 3. Can I have Ports/PortGroups with different label types grouped in
> the same SwitchingService or are they restricted to having the same
> labeltype?

Ah, excellent question. I think that NML currently defines that it is
allowed, but the meaning is undefined. I think that should change. I
like to see a SwitchingServices which supports both tagged Ethernet
(with a vlan label) as well as a untagged Ethernet (with no label). So
the requirement would be that all Port/Portgroups in a SwitchingService
MUST have the same encoding, but may have different label types.

> 4. If I can have Ports/PortGroups with different label types in the
> same SwitchingService, then does a value of labelSwapping == true
> means I can swap between different labeltypes as well?

Yes. It is currently not defined, but that is indeed a useful scenario
which should be allowed.

Indeed labelSwapping == true would mean there is no restriction with
regards to labels -- all Ports part of the SwitchingService can exchange
data without restriction.

Conversely, if labelSwapping == false, then both the type and the value
should match if data needs to be exchanged from one Port to another Port.

> If we do permit different label types in the same SwitchingService
> then adding a labelType attribute to the SwitchingService would need
> to have additional behaviour defined to restrict label swapping to
> only ports with labels of that type.

Currently, a SwitchingService does not have a labeltype attribute. It
only has a encoding attribute. (An example of encoding is "Ethernet
frames", or labeltype is "C-VLAN")


Freek