Development of standardized YANG models has seriously increased this year.
Of course, this is a good problem to have. There are close to 30 different
drafts related to YANG models for routing; coordination between these
drafts is necessary.  NETMOD is also hard at work on a backwards-compatible
YANG 1.1.  From the IETF's experience with developing MIBs, it was critical
to have the domain-area experts involved in writing and reviewing MIBs and
we believe that it is similarly critical to situate the work on YANG models
in the working groups where the appropriate domain-experts can be easily
found.  Actively encouraging and cultivating the review of those with the
expertise in modeling with YANG and deep understanding of its features is
also critical to the success of standardized YANG models.  This expertise
is found in the NETMOD working group and among the YANG doctors (
https://www.ietf.org/iesg/directorate/yang-doctors.html).

We, as the Routing and Ops and Management Area Directors, would like to see
work proceed as follows.

1) The mailing list, rtg-yang-coord@ietf.org, has been created to
coordinate among the different routing YANG models and drafts.  For
instance, there may be common groupings to be defined, interactions between
models to be determined, and so on.  To facilitate this coordination work,
we are developing a job description for a secretary for the mailing list
and hope to appoint someone to that role.

2) Routing-related YANG models must be targeted for adoption at the
appropriate WGs in the Routing Area.  If the appropriate WG is unclear,
please bring the question to the RTGWG and the rtg-yang-coord@ietf.org mailing
list.  RTGWG can either direct where the work goes or, if there is no
appropriate other WG, make a decision about adopting the draft.

3) The NETMOD charter has been open to accept work item that don't fall
under the responsibility of an existing WGs:

The NETMOD WG may also develop any additional data models written in YANG
that the WG considers core building blocks and that do not fall under the
charters of other active IETF working groups. The NETMOD WG may simply add
such milestones as it sees fit, with the advice and consent of the
responsible AD.

In case of routing-related YANG models, even if there are no responsible
existing WG, it's expected that the standardization happens in the RTGWG.

4) It is common and expected that sometimes work needs to be discussed in
multiple WGs, even though it is only adopted in one.  Examples would
include NETMOD discussing a model for OSPF to consider how it relates to
draft-ietf-netmod-routing-cfg, RTGWG discussing
draft-ietf-netmod-routing-cfg to encourage review and discussion about its
use as a base for routing-related models, etc.

5) We have heard a strong desire from the community to rapidly encourage
development of standardized YANG models.  Towards that end, we expect and
encourage more and frequent virtual interims (some probably joint between
WGs).  To have such a pace work well, we need authors, reviewers, and
contributors to expect to spend time on this work on an on-going basis.

6) Since many YANG doctors also participate in NETMOD and since NETMOD is
having weekly virtual interims, it may prove convenient to provide feedback
on YANG models in this forum.  When done so, to ensure the interested
parties are aware of the relevant models to be discussed and can arrange
their schedules to call in, the agenda should be forwarded with at least a
week's to the rtg-yang-coord@ietf.org and to the relevant WGs. When the
virtual interim is used to provide YANG doctor feedback, preference should
be given to drafts already adopted by a WG; discussing one model does not
imply partiality or a request to the WG appropriate to consider adopting
the draft.

7) To provide a common location to find proposed YANG models and be able to
verify their accuracy, Tom Nadeau, one of the NETMOD chairs, has set up a
GitHub repository at: https://github.com/YangModels/yang.  All work
contributed to it is subject to the IETF Contributions policy, as
summarized via the very very familiar IETF Note Well.
8) For the second IETF meeting in a row, a "YANG Advice and Editing
Session" (http://www.ietf.org/meeting/91/tutorials/yang-session.html) is
organized on the Sunday before the IETF meeting. This is your chance to sit
down with a YANG doctor and to get feedback on your YANG module.

If you have any questions, please let us know.

Regards,
Alia, Benoit, Adrian, & Joel