Liaison statement
Liaison on CFM YANG

Dear Colleagues,

Thank you for the information in your liaisons dated May 18, 2017 “Liaison on
YANG Model Development” and September 14, 2017 “For Action: YANG model for CFM
OAM”, and for your offer to coordinate as IEEE 802.1 seeks to deliver a YANG
model for Connectivity Fault Management (CFM, covering OpCode values 0-31 and
96-255) that can serve as the base for BBF, MEF, ITU-T (and other) models
pertaining to IEEE Std 802.1Q™-specified CFM.

We take note of your request for us to provide BBF with a first draft of our
P802.1Qcx YANG model. We will act on this request as soon as this draft becomes
available. In the meantime, we intend to continue using GitHub
(https://github.com/YangModels/yang/tree/master/standard/ieee/802.1) in support
of agile and collaborative development of this YANG model.

We would also like to remind you that P802.1Qcp will serve as a base for
P802.1Qcx. The latest P802.1Qcp YANG modules are available on our GitHub
repository and are also part of the YANG Catalog
(https://www.yangcatalog.org/yang-search/yang_tree.php?module=ieee802-dot1q-bridge).
A recent development in P802.1Qcp and, going forward in our other YANG
projects, including P802.1Qcx, is that we intend to follow the updated
Datastore guidelines produced by the IETF Network Management Datastore
Architecture Working Group in
https://tools.ietf.org/pdf/draft-ietf-netmod-revised-datastores-03.pdf.

We would like for P802.1Qcx to meet BBF needs and would therefore appreciate if
BBF could provide: - BBF’s requirements, usage scenarios, and priorities for
CFM and its YANG support in P802.1Qcx; - BBF TR-383a1 models referenced in your
latest liaison; - BBF-identified modifications (bbf2017.305) that would need to
be made to MEF 38 and 39 (since P802.1Qcx will also take as input MEF 38 and
MEF 39, as well as the corresponding errata that MEF previously identified and
communicated to us); and -BBF’s timeline for completion of the “draft CFM OAM
YANG model” you intend to publish.

This should help us better understand the scope of CFM features of interest to
BBF as well as how to take your draft CFM OAM YANG model as input to our
P802.1Qcx work.

We are particularly interested in understanding:
-If BBF requirements cover the whole set or a subset of CFM functionality
(e.g., does BBF need support for MIP/MHF creation?); and -If the use of the
“OAM” acronym in your latest liaison means that BBF has requirements beyond
those that CFM can meet (e.g., “MIP Identifiers” that are inexistent in IEEE
Std 802.1Q).

We noted that, as a rule, BBF makes an effort to reuse YANG models from other
organizations. We also noted your intention to ensure that the YANG models,
that BBF has under development, remain maximally aligned with P802.1Qcx work.
Finally, we noted your description that your shared modules are “specific to
access network equipment (e.g., BBF-specified Access Nodes and FTTdp DPUs)”. We
take these as indications that you share our interest in avoiding overlap and
duplication among YANG modules in the industry. As an example of this interest
in IEEE 802.1, at our November 2017 plenary meeting, we decided to widen the
applicability of our P802.1Xck YANG model for IEEE Std 802.1X™ Port-Based
Network Access Control to (access) interfaces (such as VDSL2) running in
“Packet Transfer Mode”.

As we move forward, we hope we can agree on timelines for our respective
projects that minimize overlap and duplication. For example, we are wondering
if the publication of your “draft CFM OAM YANG model” could be reprioritized to
maximize alignment with P802.1Qcx. At the same time, understanding BBF’s
timeline and priorities could potentially allow us to prioritize the
development of P802.1Qcx YANG modules based on BBF priorities.

IEEE 802.1 meets next January 22-26, 2018 in Geneva, Switzerland and March 5-9,
2018 in Rosemont, IL, USA. We also anticipate that a number of IEEE 802.1
participants interested in YANG work will attend the interim meeting that ITU-T
Q14/15 is planning to hold Sunday January 28, 2018 to discuss mechanisms to
ensure alignment of the IEEE 802 YANG work (P802.1Qcp, P802.1Qcx and P802.3.2
Standard for Ethernet YANG Data Model Definitions) with the Q14/15
Recommendation G.8052.1 “Transport OAM Management Information/Data Models for
Transport Ethernet Network Element”. In parallel, IEEE 802 has a YANG interest
group called YANGsters set up for discussions (website:
http://1.ieee802.org/yangsters/, mailing list: STDS-802-YANG@listserv.ieee.org,
conference calls: 6:00AM PDT the last Wednesday of the month at
https://join.me/ieee802.1). We would encourage your participation in those
discussions.

We look forward to continued collaboration on this and other topics.

Best regards,
Glenn Parsons
Chair, IEEE 802.1 WG