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Shepherd writeup

Date: 8th Dec, 2022

Based on the feedback resulting from IETF Last Call, feedback from 3GPP-IETF
Coordination team, 3GPP CT Chair and few others, we have decided to move this
document (SRv6 for Mobile User Plane - draft-ietf-dmm-srv6-mobile-uplane) on
informational track. This document is currently on track to become a Proposed
Standard. Meaning, with this change, this document upon IESG approval will be
published as an Informational RFC.

The Int Area Director (Erik Kline), ex-Int Area director (Suresh Krishnan) and
the lead document authors (Satoru, Miya, Pablo, & Daniel) and WG chair (myself)
have met few times and have agreed to implement this change.

Sri Gundavelli

Document Shepherd writeup for:

   Title:    Segment Routing IPv6 for Mobile User Plane
   Author:   Satoru Matsushima (editor), Clarence Filsfils, Miya Kohno, Pablo
   Camarillo Garvia (editor), Daniel Voyer, Charles E. Perkins Filename:

(1) What type of RFC is being requested (BCP, Proposed Standard, Internet
Standard, Informational, Experimental, or Historic)? Why is this the
proper type of RFC? Is this type of RFC indicated in the title page

Standards Track, Proposed Standard

The use of SRv6 for enabling mobile user plane requires support from multiple
network elements and with a very prescriptive behavior. This is essential for
realizing a multi-vendor eco-system and interoperability. Publishing this
behavior in a standards-track document will help realize that larger goal.  We
therefore believe “Standards Track” is the correct status for this document.

(2) The IESG approval announcement includes a Document Announcement
Write-Up. Please provide such a Document Announcement Write-Up. Recent
examples can be found in the "Action" announcements for approved
documents. The approval announcement contains the following sections:

Technical Summary:

Relevant content can frequently be found in the abstract and/or
introduction of the document. If not, this may be an indication that
there are deficiencies in the abstract or introduction.

   This document specifies the applicability of SRv6 (Segment Routing
   IPv6) to the user-plane of mobile networks.  The network programming
   nature of SRv6 accomplishes mobile user-plane functions in a simple
   manner.  The statelessness of SRv6 and its ability to control both
   service layer path and underlying transport can be beneficial to the
   mobile user-plane, providing flexibility, end-to-end network slicing,
   and SLA control for various applications.

Working Group Summary:

Was there anything in WG process that is worth noting? For example, was
there controversy about particular points or were there decisions where
the consensus was particularly rough?

There have been two WGLCs on this document. The first WGLC was issued in April
of 2021. The working group feedback from the first WGLC has identified few
technical issues which the authors have addressed over the next 11 months.
Subsequently, there was a second WGLC which was issued in April of 2022.

There have been few objections raised during the first WGLC, primarily the
concern that the document attempts to redefine 3GPP standard in an IETF
document and which is not acceptable. The authors have worked with the
reviewers and additionally based on the WG chair feedback have updated the
document. Most of the sections are now marked as informative sections. The
feedback from the second WGLC did not reflect any such major concerns, except
from one WG member who still has concerns on the scope. Other than this one
opposing view, there is considerable support from the WG for this work. Based
on the feedback received from the first and second last calls, we believe there
is rough consensus to move the document forward.

With regards to the scope of the efforts, we the chairs believe the document
does not redefine any particular SDO standard. It is not updating what is
specified in 3GPP TS 23.501 or for that matter any other specifications. The
focus of the document is about the use of IETF protocols for realizing a
specific behavior without modifying the SDO standards. It is about application
and the use of an open IETF standard protocol in a forwarding environment. No
part of this specification redefines any of the SDO interfaces. 3GPP specified
N3 and N9 interfaces or all other interfaces continue to remain the same. An
implementation is not required to implement any part of this specification for
it to be compliant to the SDO defined standards.

Document Quality:

Are there existing implementations of the protocol? Have a significant
number of vendors indicated their plan to implement the specification?
Are there any reviewers that merit special mention as having done a
thorough review, e.g., one that resulted in important changes or a
conclusion that the document had no substantive issues? If there was a
MIB Doctor, YANG Doctor, Media Type or other expert review, what was its
course (briefly)? In the case of a Media Type review, on what date was
the request posted?

This document had high visibility and it went through a thorough review
process. The quality of the document is very good. It is technically accurate
and a well written document.


Who is the Document Shepherd? Who is the Responsible Area Director?

   Sri Gundavelli is Document Shepherd.
   Erik Kline is Responsible Area Director.

(3) Briefly describe the review of this document that was performed by
the Document Shepherd. If this version of the document is not ready for
publication, please explain why the document is being forwarded to the

I as a Document Shepard and WG co-chair, have reviewed this document.

I believe this document is ready for publication and therefore we are moving
this for IESG reviews.

(4) Does the document Shepherd have any concerns about the depth or
breadth of the reviews that have been performed?


(5) Do portions of the document need review from a particular or from
broader perspective, e.g., security, operational complexity, AAA, DNS,
DHCP, XML, or internationalization? If so, describe the review that took


(6) Describe any specific concerns or issues that the Document Shepherd
has with this document that the Responsible Area Director and/or the IESG
should be aware of? For example, perhaps he or she is uncomfortable with
certain parts of the document, or has concerns whether there really is a
need for it. In any event, if the WG has discussed those issues and has
indicated that it still wishes to advance the document, detail those
concerns here.

This document went through a thorough review process. I have no concerns moving
this document forward.

(7) Has each author confirmed that any and all appropriate IPR
disclosures required for full conformance with the provisions of BCP 78
and BCP 79 have already been filed. If not, explain why?


(8) Has an IPR disclosure been filed that references this document? If
so, summarize any WG discussion and conclusion regarding the IPR

WG was made aware of the IPR declarations. There were no discussions or

(9) How solid is the WG consensus behind this document? Does it represent
the strong concurrence of a few individuals, with others being silent, or
does the WG as a whole understand and agree with it?

There is strong consensus for advancing this work. The fact that the document
went through multiple WGLC is a good indication on the level of working group
engagement. People have been quite vocal on this topic.

(10) Has anyone threatened an appeal or otherwise indicated extreme
discontent? If so, please summarise the areas of conflict in separate
email messages to the Responsible Area Director. (It should be in a
separate email because this questionnaire is publicly available.)

There is one reviewer who has concerns moving this document forward. The person
did not state if he is going to go for an appeal. He did say that he will raise
his concerns during IETF LC.

(11) Identify any ID nits the Document Shepherd has found in this
document. (See and the Internet-Drafts
Checklist). Boilerplate checks are not enough; this check needs to be

No ID nits errors are seen. Following is the Id nits summary:

Summary: 0 errors (**), 0 flaws (~~), 8 warnings (==), 2 comments (--).

(12) Describe how the document meets any required formal review criteria,
such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.

Not Applicable

(13) Have all references within this document been identified as either
normative or informative?


(14) Are there normative references to documents that are not ready for
advancement or are otherwise in an unclear state? If such normative
references exist, what is the plan for their completion?

All normative references are published RFC and external documents.

(15) Are there downward normative references references (see RFC 3967)? If so,
list these downward references to support the Area Director in the Last Call


(16) Will publication of this document change the status of any existing
RFCs? Are those RFCs listed on the title page header, listed in the
abstract, and discussed in the introduction? If the RFCs are not listed
in the Abstract and Introduction, explain why, and point to the part of
the document where the relationship of this document to the other RFCs is
discussed. If this information is not in the document, explain why the WG
considers it unnecessary.


(17) Describe the Document Shepherd's review of the IANA considerations
section, especially with regard to its consistency with the body of the
document. Confirm that all protocol extensions that the document makes
are associated with the appropriate reservations in IANA
registries. Confirm that any referenced IANA registries have been clearly
identified. Confirm that newly created IANA registries include a detailed
specification of the initial contents for the registry, that allocations
procedures for future registrations are defined, and a reasonable name
for the new registry has been suggested (see RFC 8126).


(18) List any new IANA registries that require Expert Review for future
allocations. Provide any public guidance that the IESG would find useful
in selecting the IANA Experts for these new registries.


(19) Describe reviews and automated checks performed by the Document
Shepherd to validate sections of the document written in a formal
language, such as XML code, BNF rules, MIB definitions, YANG modules,

Not applicable

(20) If the document contains a YANG module, has the module been checked
with any of the recommended validation tools
( for syntax and
formatting validation? If there are any resulting errors or warnings,
what is the justification for not fixing them at this time? Does the YANG
module comply with the Network Management Datastore Architecture (NMDA)
as specified in RFC8342?

Not Applicable