Messaging Use Cases and Extensions for STIR
draft-ietf-stir-messaging-08

Received changes through RFC Editor sync (changed state to RFC, created became rfc relationship between draft-ietf-stir-messaging and RFC 9475, changed IESG state to RFC Published)

[Ballot comment]
Changing position from Discuss.

I think that it is great that the authors adding some text into the intro that highlights that some text is normative and some is informative.  Really, I was hoping that the text would be quite specific about *which* parts of the document are normative or informative, either in the introduction or in the individual sections.  Specifically, I would regard that all sections of an Std Track RFC to be regarded as normative text unless there is an indication that it is informative – e.g., something like “This section provides non-normative guidance about …”

Having said that, this is not a critical issue, and hence I will clear the discuss and leave it to the authors and Murray, as responsible AD, to decide whether further changes would improve the clarity of this specification or whether the current version is sufficient.

[Ballot discuss]
** Format of the msgi-claim

[per -06] Section 3.2.  The format of the msgi claim is defined by a single example.  Is the format ‘{“sha256”,”sha384”,”sha512”}  ’?  Please specify it more formally.

[per -07] Thanks for adding the syntax.  The -07 syntax added the following text:

  Implementations MAY support additional
  algorithms, but MUST NOT support known weak algorithms such as MD5 or
  SHA-1.

What is the interoperable mechanism that will be used to parse and identify the hash algorithm name when an algorithm other than the ones specified here (i.e., sha256, sha384, sha512) is used?

[Ballot comment]
Hi,

Thanks for the document.

I, too, support Robert's discuss position on this.  If I were looking to do an implementation, I think I'd struggle to do so based on this document, and the document doesn't seem to adequately delineate that which is informational and that which is standards.

[Ballot comment]
I support Robert's DISCUSS

I found it quite hard to follow exactly what is in scope of this spec in Section 3.2. I gather there are certain modes of MESSAGE method that are in scope and others that aren't, but it would be useful to start 3.2 with a taxonomy of these modes and discuss what is in and out of scope. Considerations for the unsupported use cases are fine, but should be clearly separated out as such.

[Ballot comment]
Thanks to the authors for writing this - I personally find use case type documents to be really useful.

I'd also like to thank Bo Wu for the OpsDir comments (https://datatracker.ietf.org/doc/review-ietf-stir-messaging-06-opsdir-lc-wu-2022-11-19/ ) - these contain some nits and editorial comments that the authors should address when folding in other comments.

I'm following John's position here: the document is mostly narrative, but that's fine with me too (AKA: ¯\_(ツ)_/¯)

[Ballot comment]
Like others I took note of the fact that this document contains an itty-bitty piece of bonafide specification [*] surrounded by a great deal of lucid, interesting, but ultimately speculative and inconclusive prose.

Unlike others I'm at peace with that.

[*] Paragraphs two and three of Section 3.2.

[Ballot discuss]

# Éric Vyncke, INT AD, comments for draft-ietf-shmoo-hackathon-07
CC @evyncke

Thank you for the work put into this document.

Please find below one blocking DISCUSS point, some non-blocking COMMENT points (but replies would be appreciated even if only for my own education).

Please note that Wassim Haddad is the Internet directorate reviewer (at my request) and you may want to consider this int-dir reviews as well when Wassim will complete the review (no need to wait for it though):
https://datatracker.ietf.org/doc/draft-ietf-stir-messaging/reviewrequest/16757/

Special thanks to Ben Campbell for the shepherd's detailed write-up including the WG consensus *and* the justification of the intended status.

I hope that this review helps to improve the document,

Regards,

-éric


## DISCUSS

As noted in https://www.ietf.org/blog/handling-iesg-ballot-positions/, a DISCUSS ballot is a request to have a discussion on the following topics:

### Section 3.2

Very easy to fix but is there a registry for the leading strings 'sha256', ... ? How can it be extended ? What is the exact syntax ?

Is there a potential negotiation of support hash algorithms between the parties ? What is the expected error code when the receiver does not support this algo ?

[Ballot comment]

## COMMENTS

### Unused reference

If the idnits https://author-tools.ietf.org/api/idnits?url=https://www.ietf.org/archive/id/draft-ietf-stir-messaging-06.txt can be trusted, then please fix all unused references.

### Using SIP for messaging

I must admit my ignorance on this topic, but I would assume that most of the messaging system (from Skype to WhatsApp and others) do not rely on SIP, so this I-D may not be that useful or do I miss something ?

### Usefulness of "msgi"

Please educate me (probably obvious to you) about the usefulness of "msgi", is the SIP header integrity protected while the body is not ? Then, this would make perfect sense.

### Section 1
```
  As telephone services
  are increasingly migrating onto the Internet and using Voice over IP
  (VoIP) protocols such as SIP [RFC3261]
```
Perhaps naively, I would have assumed that in 2022 the migration/transition is mostly done. Should this text be refreshed ?


## Notes

This review is in the ["IETF Comments" Markdown format][ICMF], You can use the
[`ietf-comments` tool][ICT] to automatically convert this review into
individual GitHub issues.

[ICMF]: https://github.com/mnot/ietf-comments/blob/main/format.md
[ICT]: https://github.com/mnot/ietf-comments

[Ballot discuss]
Hi,

Thanks for writing this document.  I share the concerns raised by Paul but have elevated them to Discuss level so that we can have a discussion.  The category of the document (i.e., a formal standards track specification) doesn't seem to align with most of the prose that is vague.  Specifically, I don't know how the majority of this document could be implemented as specification.

It looks like the "Passport Extension" IANA Registry is only specification required, so one solution would be for this document to be made informational or experimental.

Otherwise, I think that this document would benefit from a much clearer and precise split between what part of the document defines the formal specification, and which part is just informative guidance.

Regards,
Rob

[Ballot comment]
Note I find the overall text very vague:

"This specification therefore explores", " there are a few ways that the PASSporT mechanism of STIR could apply to messaging:", "This could be applicable to MSRP sessions", "An Identity header could be added to any SIP MESSAGE request", "PASSporT can provide its own integrity check", "the PASSporT could be conveyed in an Identity header".

If it wasn't for the IANA registration and Section 3.2, I would have thought Informational or Experimental would have been better.

[Ballot discuss]
** Section 3.2.  The format of the msgi claim is defined by a single example.  Is the format ‘{“sha256”,”sha384”,”sha512”}  ’?  Please specify it more formally.

** Section 4.
  Thus any store-and-forward messaging
  system relying on PASSporTs must take into account the possibility
  that the certificate that signed the PASSporT, though valid at the
  time the PASSporT was generated, could expire before a user reads the
  message.  This might require storing some indicator of the validity
  of the signature and certificate at the time the message was
  received, or securely storing the certificate along with the
  PASSporT, so that the "iat" field can be compared the expiry window
  of the certificate prior to validation.

Please correct me here if I am misunderstanding the deployed STIR architecture:

-- Why is the time the user reads the message relevant?  Isn’t the verification done by either the proxy or UA at the time of receipt (irrespective of when it is read)?

-- How would the verification process work if the certificate was expired?  As some short-lived certificates are used instead of revocation, how would a verifier distinguish that.

-- Who is the guidance of storing additional state directed at – all verifiers? verification proxies?

[Ballot comment]
** idnits returned:
  == Unused Reference: 'RFC4474' is defined on line 392, but no explicit
    reference was found in the text

  == Unused Reference: 'RFC7159' is defined on line 398, but no explicit
    reference was found in the text

  == Unused Reference: 'RFC3311' is defined on line 437, but no explicit
    reference was found in the text

  == Unused Reference: 'RFC4916' is defined on line 445, but no explicit
    reference was found in the text

** Section 3.1.  In the spirit of inclusive language, please rephrase “man-in-the-middle attacks”.

** Section 3.2.  Please provide a bit more explanation on a “cut-and-paste attack” either inline or with citation.  Perhaps “A cut-and-paste attack is one where the Identity header field from a legitimate request for one user is reused into a request for a different user.” (from RFC8224)

** Section 3.2.
  The interaction of [RFC8226] STIR certificates with S/
  MIME for messaging applications requires some further explication;
  and additionally,

Where is using STIR certificates with S/MIME explained?

** Section 3.2.  Editorial.
  In order to differentiate a PASSporT for an individual message from a
  PASSporT used to secure a telephone call or message stream, this
  document defines a new "msg" PASSporT Type

It would be helpful to clarify that the behavior being described here is extending PASSporT via a “ppt” claim set to “msg”

** Section 3.2.  What is the expected approach for hash algorithm agility?

** Section 3.2.

  Any such environment would require a profile of
  this specification that reduces the scope of protection only to the
  CPIM payload, as discussed in [RFC8946] Section 9.1.

Section 9.1 of RFC8946 doesn’t explain any CPIM mechanism or a way to reduce the scope of a protection. 

** Section 3.2.
  The
  potential for replay attacks can, however, be largely mitigated by
  the timestamp in PASSporTs; duplicate messages are easily detected,
  and the timestamp can order mesages displayed to the user inbox in a
  way that precludes showing stale messages as fresh.

-- Can the approach by which replay attacks are mitigated be clarified?  It looks like the text is saying deliver all messages, sort them by timestamp and by human inspection the “replay attack” is mitigated.
-- Typo. s/mesages/messages/

** Section 3.2.  When in the hash conveyed in the msgi claim checked relative to the verification procedures of Section 6.2 of RFC8224?  What is the expected error handling if the hash does not match?

** Section 3.2.  Editorial. In this discussion of messaging, it would be helpful to clearly state the applicability/scope of the new ppt=”msg” extension.  I think it intended only for messaged conveyed via SIP via the MESSAGE method.

** Section 3.2.
  In such cases, the expiry timers recommended by
  [RFC8224] may be too strict, as routine behavior might dictate the
  delivery of a MESSAGE minutes or hours after it was sent. 

I couldn’t find a use of the term “timer” in RFC8224.  Is this text referring to Step 4 of Section 6.2 of RFC8224 which notes the need for checking whether a message meets freshness according to local policy and RECOMMENDS 60 seconds? If so, please make the language more consistent (and/or provide a reference into RFC8224).

** Section 3.2.1.  Editorial. Note that using PASSporT for any protocols other than SIP is also out of scope (the same way support for MMS with SMTP is out of scope)

** Section 3.2.1. Is the “SMPP” referenced here “Short Message Peer-to-Peer Protocol”?  Can this be expanded and cited?

** Section 4.  Editorial.
... so that the "iat" field can be compared the expiry window
  of the certificate prior to validation.

There is a missing word here.

** Section 8. The second paragraph appears to be commenting on behavior not described by this document.  Is it needed?

(Via drafts-lastcall@iana.org): IESG/Authors/WG Chairs:

The IANA Functions Operator has completed its review of draft-ietf-stir-messaging-06. If any part of this review is inaccurate, please let us know.

The IANA Functions Operator understands that, upon approval of this document, there are two actions which we must complete.

First, in the JSON Web Token Claims registry on the JSON Web Token registry page located at:

https://www.iana.org/assignments/jwt/

a single new Claim Name is to be registered as follows:

Claim Name: msgi
Claim Description: Message Integrity Information
Change Controller: IESG
Reference: [ RFC-to-be ]

IANA question --> Would it be acceptable to list the IETF as the change controller for the JSON Web Token Claim registration instead of the IESG? There has been a preference for doing so, as described in the expired document at https://datatracker.ietf.org/doc/html/draft-leiba-ietf-iana-registrations-00, but it hasn\u2019t been recorded in a permanent document yet.

As this document requests registrations in a Specification Required (see RFC 8126) registry, we will initiate the required Expert Review via a separate request. This review must be completed before the document's IANA state can be changed to "IANA OK."

Second, in the Personal Assertion Token (PASSporT) Extensions registry on the Personal Assertion Token (PASSporT) registry page located at:

https://www.iana.org/assignments/passport/

a new extension is to be registered as follows:

ppt value: msg
Reference: [ RFC-to-be, Section 3.2 ]

As this also requests registrations in a Specification Required (see RFC 8126) registry, we will initiate the required Expert Review via a separate request. This review must be completed before the document's IANA state can be changed to "IANA OK."

The IANA Functions Operator understands that these are the only actions required to be completed upon approval of this document.

Note:  The actions requested in this document will not be completed until the document has been approved for publication as an RFC. This message is meant only to confirm the list of actions that will be performed.

For definitions of IANA review states, please see:

https://datatracker.ietf.org/help/state/draft/iana-review

Thank you,

Sabrina Tanamal
Lead IANA Services Specialist

The following Last Call announcement was sent out (ends 2022-11-03):

From: The IESG
To: IETF-Announce
CC: ben@nostrum.com, draft-ietf-stir-messaging@ietf.org, stir-chairs@ietf.org, stir@ietf.org, superuser@gmail.com
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (Messaging Use Cases and Extensions for STIR) to Proposed Standard


The IESG has received a request from the Secure Telephone Identity Revisited
WG (stir) to consider the following document: - 'Messaging Use Cases and
Extensions for STIR'
  as Proposed Standard

The IESG plans to make a decision in the next few weeks, and solicits final
comments on this action. Please send substantive comments to the
last-call@ietf.org mailing lists by 2022-11-03. Exceptionally, comments may
be sent to iesg@ietf.org instead. In either case, please retain the beginning
of the Subject line to allow automated sorting.

Abstract


  Secure Telephone Identity Revisited (STIR) provides a means of
  attesting the identity of a telephone caller via a signed token in
  order to prevent impersonation of a calling party number, which is a
  key enabler for illegal robocalling.  Similar impersonation is
  sometimes leveraged by bad actors in the text and multimedia
  messaging space.  This document explores the applicability of STIR's
  Personal Assertion Token (PASSporT) and certificate issuance
  framework to text and multimedia messaging use cases, including
  support both for messages carried as a payload in SIP requests and
  for messages sent in sessions negotiated by SIP.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-stir-messaging/



No IPR declarations have been submitted directly on this I-D.

# Document Shepherd Write-Up for Group Documents

*This version is dated 4 July 2022.*

## 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 consensus represented discussion among a fairly small group. The consensus
  among the group was strong, and no one raised material objections to the work.

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?
 
  There was no significant controversy.

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.)
 
  No one has indicated 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
  (where)?
 
  The shepherd is not aware of existing implementations. There have been statements
  that the work is needed by the emergency services community. Otherwise, like
  much of the work of STIR, implementation depends upon the work being used by
  other fora that define messaging systems and inter-carrier interoperability,
  such as the 3GPP, the GSMA, or ATIS.

## 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.
 
  Like much of STIR work, the document closely interacts with SIP, which is maintained
  by SIPCORE. There is significant cross-participation between STIR and SIPCORE, so
  it explicit reviews in SIPCORE do not seem necessary.

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.
 
  The shepherd is not aware of the need for any such formal review.

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 draft does not contain YANG.

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 draft does not use formal languages.

## 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 draft shepherd believes this draft is ready to be handed off to the AD.

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
    reviews?
   
    The shepherd has not identified any such issues.

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 expected status is Proposed Standard. This is correctly indicated in the
    datatracker and on the first page. This draft standardizes a new PASSporT type
    and procedures for using it.

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 authors have explicitly indicated that there are no IPR disclosures have
    been made or are needed.
   
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.
   
    Both authors have explicitly indicated their willingness to be listed.

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
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)
   
    The only unresolved nits the shepherd is aware of are some uncited normative
    references (RFCs 4474, 7159, 3311, and 4916), which should be removed (or cited) in the next revision. This does
    not seem to be serious enough to delay the publication request.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].
   
    The shepherd believes that the references are correctly categorized.

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

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.
   
    There are no normative downrefs.

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 to published 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 does not change any existing document status.

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 IANA considerations section is complete and correct. Both referenced
    registries are clearly identified. The draft does not create any new registries.

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.
   
    There are no new registries.

# Document Shepherd Write-Up for Group Documents

*This version is dated 4 July 2022.*

## 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 consensus represented discussion among a fairly small group. The consensus
  among the group was strong, and no one raised material objections to the work.

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?
 
  There was no significant controversy.

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.)
 
  No one has indicated 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
  (where)?
 
  The shepherd is not aware of existing implementations. There have been statements
  that the work is needed by the emergency services community. Otherwise, like
  much of the work of STIR, implementation depends upon the work being used by
  other fora that define messaging systems and inter-carrier interoperability,
  such as the 3GPP, the GSMA, or ATIS.

## 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.
 
  Like much of STIR work, the document closely interacts with SIP, which is maintained
  by SIPCORE. There is significant cross-participation between STIR and SIPCORE, so
  it explicit reviews in SIPCORE do not seem necessary.

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.
 
  The shepherd is not aware of the need for any such formal review.

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 draft does not contain YANG.

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 draft does not use formal languages.

## 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 draft shepherd believes this draft is ready to be handed off to the AD.

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
    reviews?
   
    The shepherd has not identified any such issues.

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 expected status is Proposed Standard. This is correctly indicated in the
    datatracker and on the first page. This draft standardizes a new PASSporT type
    and procedures for using it.

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 authors have explicitly indicated that there are no IPR disclosures have
    been made or are needed.
   
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.
   
    Both authors have explicitly indicated their willingness to be listed.

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
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)
   
    The only unresolved nits the shepherd is aware of are some uncited normative
    references (RFCs 4474, 7159, 3311, and 4916), which should be removed (or cited) in the next revision. This does
    not seem to be serious enough to delay the publication request.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].
   
    The shepherd believes that the references are correctly categorized.

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

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.
   
    There are no normative downrefs.

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 to published 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 does not change any existing document status.

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 IANA considerations section is complete and correct. Both referenced
    registries are clearly identified. The draft does not create any new registries.

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.
   
    There are no new registries.

# 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 consensus represented discussion among a fairly small group. The consensus
  among the group was strong, and no one raised material objections to the work.

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?
 
  There was no significant controversy.

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.)
 
  No one has indicated 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
  (where)?
 
  The shepherd is not aware of existing implementations. There have been statements
  that the work is needed by the emergency services community. Otherwise, like
  much of the work of STIR, implementation depends upon the work being used by
  other fora that define messaging systems and inter-carrier interoperability,
  such as the 3GPP, the GSMA, or ATIS.

## 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.
 
  Like much of STIR work, the document closely interacts with SIP, which is maintained
  by SIPCORE. There is significant cross-participation between STIR and SIPCORE, so
  it explicit reviews in SIPCORE do not seem necessary.

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.
 
  The shepherd is not aware of the need for any such formal review.

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 draft does not contain YANG.

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 draft does not use formal languages.

## 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 draft shepherd believes this draft is ready to be handed off to the AD.

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
    reviews?
   
    The shepherd has not identified any such issues.

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 expected status is Proposed Standard. This is correctly indicated in the
    datatracker and on the first page. This draft standardizes a new PASSporT type
    and procedures for using it.

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 authors have explicitly indicated that there are no IPR disclosures have
    been made or are needed.
   
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.
   
    Both authors have explicitly indicated their willingness to be listed.

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
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)
   
    The only unresolved nits the shepherd is aware of are some uncited normative
    references (RFCs 4474, 7159, 3311, and 4916), which should be removed (or cited) in the next revision. This does
    not seem to be serious enough to delay the publication request.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].
   
    The shepherd believes that the references are correctly categorized.

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

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.
   
    There are no normative downrefs.

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 to published 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 does not change any existing document status.

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 IANA considerations section is complete and correct. Both referenced
    registries are clearly identified. The draft does not create any new registries.

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.
   
    There are no new registries.