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Shepherd writeup

# Document Shepherd Write-Up for Group Documents

*This version is dated 4 July 2022.*

Thank you for your service as a document shepherd. Among the responsibilities is
answering the questions in this write-up to give helpful context to Last Call
and Internet Engineering Steering Group ([IESG][1]) reviewers, and your
diligence in completing it is appreciated. The full role of the shepherd is
further described in [RFC 4858][2]. You will need the cooperation of the authors
and editors to complete these checks.

Note that some numbered items contain multiple related questions; please be sure
to answer all of them.

## Document History

1. Does the working group (WG) consensus represent the strong concurrence of a
   few individuals, with others being silent, or did it reach broad agreement?

The work was started in the 6MAN WG on a request from the SPRING WG chairs (,
see Section 9 of this write-up for more details). The draft was discussed
extensively in 6MAN and in SPRING. The document received strong support from
multiple individuals.

WGLC thread:

2. Was there controversy about particular points, or were there decisions where
   the consensus was particularly rough?

No controversy or particularly rough consensus were observed. The discussion on
the mailing list was extensive and productive, but not rough. The SPRING
co-chair (Joel Halpern) also reviewed the document and confirmed that he is
happy with the draft.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If
   so, please summarize 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.)

Nobody has  threatened an appeal or otherwise indicated extreme discontent.

4. For protocol documents, are there existing implementations of the contents of
   the document? Have a significant number of potential implementers indicated
   plans to implement? Are any existing implementations reported somewhere,
   either in the document itself (as [RFC 7942][3] recommends) or elsewhere

This is not a protocol document.

This document is informational and doesn’t require any implementation. (If
future SRv6 deployments start using the allocated /16 for SIDs it could be
considered an implementation, but it’s not going to happen until the IANA
allocation is made).

## Additional Reviews

5. Do the contents of this document closely interact with technologies in other
   IETF working groups or external organizations, and would it therefore benefit
   from their review? Have those reviews occurred? If yes, describe which
   reviews took place.

This document closely interacts with SPRING, as the goal of the draft  is to
clarify the relationship between SRv6 SIDs  and IPv6 addressing architecture.

Every revision of the draft (before and after adoption) was actively discussed
in SPRING WG, which was also copied (and actively participated) in the WGLC

The SPRING co-chair (Joel Halpern) also reviewed the document and confirmed
that he is happy with the draft.

As the draft suggested some action items for the SPRING
draft-ietf-spring-srv6-srh-compression document,  github issues were opened for
draft-ietf-spring-srv6-srh-compression and have been resolved by the SPRING WG:

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

No such review is needed.

7. If the document contains a YANG module, has the final version of the module
   been checked with any of the [recommended validation tools][4] 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 [RFC 8342][5]?

The document doesn’t contain any YANG module.

8. Describe reviews and automated checks performed to validate sections of the
   final version of the document written in a formal language, such as XML code,
   BNF rules, MIB definitions, CBOR's CDDL, etc.

The document doesn’t contain any such formal language.

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this
   document is needed, clearly written, complete, correctly designed, and ready
   to be handed off to the responsible Area Director?

The document was created on request and with the collaboration of the SPRING WG.

During the adoption of draft-filsfilscheng-spring-srv6-srh-compression
(replaced by draft-ietf-spring-srv6-srh-compression) a number of questions were
raised regarding relationship between SRv6 SIDs (esp. C-SIDs) and IPv6
addresses as defined in RFC4291 and RFC8200): while SIDs are 128-bits
identifiers placed into the Destination Address field of an IPv6 header, they
are semantically different. Both SPRING and 6MAN WGs believe that some
clarification is needed to ensure that using C-SIDs do not conflict with IPv6
address architecture and data plane behavior.

After an extensive discussion in  6MAN and SPRING WGs
the chairs and ADs suggested
writing a document to clarify and categorize SRv6 SIDs, especially how they are
related to IPv6 addresses.

 Both WGs and the shepherd believe that the document is needed, especially for
 advancing draft-ietf-spring-srv6-srh-compression.

The shepherd believes that the document is clearly written, complete and ready
to be handed off to the responsible Area Director.

10. Several IETF Areas have assembled [lists of common issues that their
    reviewers encounter][6]. For which areas have such issues been identified
    and addressed? For which does this still need to happen in subsequent

As the document discusses the relationship between IPv6 addresses and SRv6
SIDs, most of the issues listed in [6] are not applicable. In particular, the
document doesn’t cover any topics from ART, Ops, Routing, Sec and TSV sections
of [6]. The document looks good in regards to issues defined in

11. What type of RFC publication is being requested on the IETF stream ([Best
    Current Practice][12], [Proposed Standard, Internet Standard][13],
    [Informational, Experimental or Historic][14])? Why is this the proper type
    of RFC? Do all Datatracker state attributes correctly reflect this intent?

The draft is requested to be published as an Informational document. This is
the most suitable type, as this document doesn’t define a protocol, a procedure
or a format.

While it requests an IANA allocation and recommends that SRv6 deployments are
using that dedicated block, that doesn’t seem to be sufficient to classify the
document as BCP.

12. Have reasonable efforts been made to remind all authors of the intellectual
    property rights (IPR) disclosure obligations described in [BCP 79][7]? To
    the best of your knowledge, have all required disclosures been filed? If
    not, explain why. If yes, summarize any relevant discussion, including links
    to publicly-available messages when applicable.

The author confirmed that they are not  aware of any IPR claims related to

13. Has each author, editor, and contributor shown their willingness to be
    listed as such? If the total number of authors and editors on the front page
    is greater than five, please provide a justification.

Yes the sole author of the document is willing to be listed as such.

14. Document any remaining I-D nits in this document. Simply running the [idnits
    tool][8] is not enough; please review the ["Content Guidelines" on][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)

The -03 version of the draft was checked against and the idnits tool was
run. Two issues identified by idnits tool will be fixed in -04 (confirmed with
the author). No other issues were found.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].

The informative references are either only providing additional information or
drafts in progress. None of those references shall be normative instead. The
normative references listed in the draft are required to understand the draft
in question, hence they shall stay normative.

16. List any normative references that are not freely available to anyone. Did
    the community have sufficient access to review any such normative

All normative references are RFCs, hence freely available to anyone.

17. Are there any normative downward references (see [RFC 3967][9] and [BCP
    97][10]) that are not already listed in the [DOWNREF registry][17]? If so,
    list them.

No such references.

18. Are there normative references to documents that are not ready to be
    submitted to the IESG for publication or are otherwise in an unclear state?
    If so, what is the plan for their completion?

All normative references are RFCs.

19. Will publication of this document change the status of any existing RFCs? If
    so, does the Datatracker metadata correctly reflect this and are those RFCs
    listed on the title page, in the abstract, and discussed in the
    introduction? If not, explain why and point to the part of the document
    where the relationship of this document to these other RFCs is discussed.

This document doesn’t update/change the status of any existing RFC.

20. 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 aspects of the document requiring IANA assignments are
    associated with the appropriate reservations in IANA registries. Confirm
    that any referenced IANA registries have been clearly identified. Confirm
    that each newly created IANA registry specifies its initial contents,
    allocations procedures, and a reasonable name (see [RFC 8126][11]).

The document asks IANA to reserve /16 for a Global Unicast Prefix for SIDs. The
registry (the Internet Protocol Version 6 Address Space) and the range
(“reserved for IETF”) are clearly identified in the document. Overall, the IANA
 considerations section is clear.

21. List any new IANA registries that require Designated Expert Review for
    future allocations. Are the instructions to the Designated Expert clear?
    Please include suggestions of designated experts, if appropriate.

No new IANA registries are proposed by this document.