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Re: [Teas] Yangdoctors last call review of draft-ietf-teas-yang-te-topo-08
2017-06-22 05:12:13
Dear draft-ietf-teas-yang-te-topo authors,
Hi Xufeng,
OK, by tooling, I don't mean the pyang plugins that I have been
working on to convert between different types of models. As you
aware, the TE YANG models can easily be converted to NMDA style since
I have already done it
(https://github.com/rgwilton/ietf-models-to-combined).
My comment actually relates to the fact the structure used by TE YANG
modules don't match any other YANG modules - they are using their own
unique style of structure.
This is an important issue to resolve.
Today, there are three common styles of modules:
(1) IETF style split config/state trees (e.g. ietf-interfaces).
(2) IETF NMDA style combined config/state trees (i.e. where all IETF
modules are heading to).
(3) OpenConfig style modules with the config/state containers
immediately above the config leaves.
Tooling is likely to be optimized to work with these model structures,
but the TE modules do not fit into any of the three styles above.
They are a yet another OpenConfig-like style, but that is different
enough that tooling that is designed to work with OpenConfig style
YANG modules would likely not work with the TE YANG modules.
Specifically, for clients that expecting to work with an OpenConfig
style YANG module, then if it knows the path to config leaf X, then
they would expect the applied config value to be available at the path
"../state/X". But, this doesn't hold for the structure being used in
the TE YANG models.
I believe strongly that the models being produced by organizations
should be structures in a consistent way, hence why I think that the
published standard version of the TE YANG modules should immediately
align to the NMDA style.
Agreed.
Here is the OPS and RTG AD message:
https://www.ietf.org/mail-archive/web/netmod/current/msg18252.html
I understand that the I2RS topology YANG modules will be improved to the
NMDA style.
Regards, Benoit
Thanks,
Rob
On 22/06/2017 04:16, Xufeng Liu wrote:
Hi Rob,
While the tooling is very nice to have, especially for writing new
models or converting models, we do not have to use it for every
model. It seems not necessary to use the tooling on this model for
now. We already know that we can manually convert it to NMDA style if
needed.
Thanks,
- Xufeng
-----Original Message-----
From: Robert Wilton [mailto:rwilton(_at_)cisco(_dot_)com]
Sent: Wednesday, June 21, 2017 5:34 AM
To: Xufeng Liu <Xufeng_Liu(_at_)jabil(_dot_)com>; Mahesh Jethanandani
<mjethanandani(_at_)gmail(_dot_)com>; yang-doctors(_at_)ietf(_dot_)org
Cc: ietf(_at_)ietf(_dot_)org; teas(_at_)ietf(_dot_)org;
draft-ietf-teas-yang-te-topo(_dot_)all(_at_)ietf(_dot_)org
Subject: Re: [Teas] Yangdoctors last call review of
draft-ietf-teas-yang-te-topo-
08
Hi Xufeng,
On 12/06/2017 22:28, Xufeng Liu wrote:
Hi Mahesh,
Thank you much for the review. We have submitted an updated draft
(https://tools.ietf.org/html/draft-ietf-teas-yang-te-topo-09) to
address these
issues. More detailed explanations are put below inline.
If the responses and updates are satisfactory, we are ready for the
last call.
Best regards,
- Xufeng
-----Original Message-----
From: Mahesh Jethanandani [mailto:mjethanandani(_at_)gmail(_dot_)com]
Sent: Wednesday, May 24, 2017 11:44 AM
To: yang-doctors(_at_)ietf(_dot_)org
Cc: ietf(_at_)ietf(_dot_)org; teas(_at_)ietf(_dot_)org;
draft-ietf-teas-yang-te-topo(_dot_)all(_at_)ietf(_dot_)org
Subject: Yangdoctors last call review of
draft-ietf-teas-yang-te-topo-08
Reviewer: Mahesh Jethanandani
Review result: Ready with Issues
Document reviewed: draft-ietf-teas-yang-te-topo-08
Status: Ready with Issues
I am not an expert in Traffic Engineering. This review is looking at
the draft from a YANG perspective. With that said, I have marked
it as “Ready
with Issues”
because of some of the points discussed below.
Summary:
This document defines a YANG data model for representing, retrieving
and manipulating TE Topologies. The model serves as a base model that
other technology specific TE Topology models can augment.
Comments:
Almost all the containers in the model are presence containers. Is
there a reason why they have to be presence containers? Note, that
presence containers are containers whose existence itself represents
configuration data. What particular configuration data is each
container
representing in itself?
[Xufeng] Containers that use “presence” are:
- Container “underlay”
o We have changed 13 occurrences of such containers to be not
presence container.
- Container “te” under augmentation
o To indicate that “TE” is enabled (configuration data)
o Also used to do augmentation. The “presence” statement can
prevent the mandatory child from affecting augmented base model.
- /nw:networks/nw:network/nw:network-types/te-topology!
o A mechanism required by I2RS topology model to specify the
topology type.
It is difficult to co-relate the diagram with the model itself
because of different terms being used to define different parts of
the model.
There is “TE Topology Model” and then there is “Generic TE Topology
Model”.
Are these one and the same models? If so, a common term for both of
them would be helpful.
[Xufeng] Yes. These two terms are the same. Figure 12, Figure 13,
and relevant
descriptions have been updated to make the document consistent.
There is extensive use of groupings in the document. However, not all
instances of groupings are used multiple number of times. Where they
are not being repeated, it would be better to move the grouping
directly where the uses statement resides. Case in point the grouping
connectivity-label-restriction-list.
[Xufeng] We have removed the following groupings
te-link-augment
te-node-augment
te-termination-point-augment
te-topologies-augment
te-topology-augment
te-link-state-underlay-attributes
te-node-state-derived-notification
te-topology-type
The remaining groupings have been kept so that we can:
- Share the groupings in this model
- Prepare to be shared by a model augmenting this model
- Prevent a grouping or configuration section from being too long
- Improve readability
The split between config and state containers does not seem to follow
any particular pattern.
[Xufeng] The pattern is clear:
For each manageable entity (object), there is a config container
and state
container. The configurable properties go into the config container
and state
properties go into the state container. Such objects are identified
by a list item
or a presence container so that the “create”, “delete”, and “modify”
operations
can be performed on them. The non-presence containers do not represent
configuration data so they do not introduce such objects.
It is neither a top level split, as is the case with existing IETF
models,
[Xufeng] We could not do top level split because the base I2RS network
topology model
(https://tools.ietf.org/html/draft-ietf-i2rs-yang-network-topo-
12) that we augment does not have the top-level split (for its own
reasons).
nor do they follow the OpenConfig style of splitting config and state
under each relevant leaf,
[Xufeng] The pattern is consistent with this style in principle,
with some
adjustments to fit to our multiple levels of hierarchy.
This is effectively a new forth style of YANG models that is not
consistent with
any of the three existing styles, i.e.:
- Current IETF config/state split model style
- NMDA combined config/state tree
- OpenConfig split config/state containers immediately above the
config true
leaves.
Tooling that it designed to work with OpenConfig models will need
customization to work with these TE models because the config/state
containers will not be where the tooling expects them to be.
Thanks,
Rob
.
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