[netmod] Question on draft-ietf-netmod-yang-model-classification

["Adrian Farrel" <[e-mail]>]

Hi,

We've been trying to ensure that draft-wu-opsawg-service-model-explained is
consistent with the latest version of
draft-ietf-netmod-yang-model-classification. In discussions with Tianran a
question has come up.

In section 2 you have a nice definition of Network Service YANG Modules and this
definition maps nicely to our definition of "service delivery models".
Furthermore, your figure 1 shows Network Service YANG Modules on the interface
between OSS/BSS and the various network services.

We have further defined "customer service models" at a higher layer still. That
is, on the interface to the customer. This (of course?) assumes that the OSS/BSS
is not customer code :-)

However, your discussion of Network Service YANG Modules in section 2.1 seems
slightly at odds, although this may be just ambiguity.

For example, when you say, "Network Service YANG Modules describe the
characteristics of a service, as agreed upon with consumers of that service,"
this is not the same as, "This model is used in the discussion between a
customer and a service provide to describe the characteristics of a service."
That is, the former case could be arrived at after processing based on the
latter case - processing that we have called "service orchestration" but might
(of course) be what leads to the operator poking the OSS/BSS.

This might all be fine and good, but later in the same section you say "Network
Service YANG Modules define service models to be consumed by external systems.
These modules are commonly designed, developed and deployed by network
infrastructure teams." And there you introduce two terms that are previously
undefined and only server to add ambiguity. Specifically "external to what?" I
could make and argument that the OSS is developed and deployed by network
infrastructure teams, ad also that the OSS is external to the network itself.

And, in between these two quoted pieces of text, you have...

   As an example, the Network Service YANG Module defined in
   [YANG-Data-Model-for-L3VPN-service-delivery] provides an abstract
   model for Layer 3 IP VPN service configuration.

Per my other email, this reference needs to be fixed. But I struggle to see the
L3SM module as consistent with your figure. It may or may not be consistent with
your text dependent on the interpretation.

In draft-wu-opsawg-service-model-explained Figure 4 we have tried to show how we
(the authors) think L3SM fits into your classification. Here we place L3SM
further up the layering stack.

[Apologies for not spotting this sooner. The citation
"YANG-Data-Model-for-L3VPN-service-delivery" includes the term "service
delivery" which I took to imply a different module.]

Thanks,
Adrian