A P-Served-User Header Field Parameter for an Originating Call Diversion (CDIV) Session Case in the Session Initiation Protocol (SIP)
draft-ietf-sipcore-originating-cdiv-parameter-08

Received changes through RFC Editor sync (created alias RFC 8498, changed title to 'A P-Served-User Header Field Parameter for an Originating Call Diversion (CDIV) Session Case in the Session Initiation Protocol (SIP)', changed abstract to 'The P-Served-User header field was defined based on a requirement from the 3rd Generation Partnership Project (3GPP) IMS (IP Multimedia Subsystem) in order to convey the identity of the served user, his/ her registration state, and the session case that applies to that particular communication session and application invocation.  A session case is metadata that captures the status of the session of a served user regardless of whether or not the served user is registered or the session originates or terminates with the served user.  This document updates RFC 5502 by defining a new P-Served-User header field parameter, "orig-cdiv".  The parameter conveys the session case used by a proxy when handling an originating session after Call Diversion (CDIV) services have been invoked for the served user.  This document also fixes the ABNF in RFC 5502 and provides more guidance for using the P-Served-User header field in IP networks.', changed pages to 15, changed standardization level to Informational, changed state to RFC, added RFC published event at 2019-02-14, changed IESG state to RFC Published, created updates relation between draft-ietf-sipcore-originating-cdiv-parameter and RFC 5502)

[Ballot comment]
Section 6.2
 
  sessioncase-param        = "sescase" EQUAL ("orig"/"term")/ orig-cdiv

It's quite possible I'm just confused about the ABNF, but why do we need the
grouping?

[Ballot comment]
It seems to me that the title and abstract aren't particularly useful in helping a reader determine whether this is a document that's useful to read.

The information in the Introduction helps a LOT (starting with the point that this work is done in response to requirements from 3GPP). Is it possible that part of that information could appear in the title and abstract, to make this document more accessible?

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

The IANA Functions Operator has completed its review of draft-ietf-sipcore-originating-cdiv-parameter-05. 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 Header Fields registry on the Session Initiation Protocol (SIP) Parameters registry page located at:

https://www.iana.org/assignments/sip-parameters/

the existing entry for P-Served-User will be changed to:

Header Name: P-Served-User
compact: none
Reference: [RFC5502][ RFC-to-be ]

Second, in the Header Field Parameters and Parameter Values registry also on the Session Initiation Protocol (SIP) Parameters registry page located at:

https://www.iana.org/assignments/sip-parameters/

three, new registrations are to be made as follows:

Header Field: P-Served-User
Parameter Name: sescase
Predefined Values: Yes
Reference: [RFC5502]

Header Field: P-Served-User
Parameter Name: regstate
Predefined Values: Yes
Reference: [RFC5502]

Header Field: P-Served-User
Parameter Name: orig-cdiv
Predefined Values: No
Reference: [ RFC-to-be ]

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.

Thank you,

Sabrina Tanamal
Senior IANA Services Specialist

The following Last Call announcement was sent out (ends 2018-10-26):

From: The IESG
To: IETF-Announce
CC: ben@nostrum.com, Jean Mahoney , sipcore-chairs@ietf.org, sipcore@ietf.org, mahoney@nostrum.com, draft-ietf-sipcore-originating-cdiv-parameter@ietf.org
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (A P-Served-User Header Field Parameter for Originating CDIV session case in Session Initiation Protocol (SIP)) to Informational RFC


The IESG has received a request from the Session Initiation Protocol Core WG
(sipcore) to consider the following document: - 'A P-Served-User Header Field
Parameter for Originating CDIV session
  case in Session Initiation Protocol (SIP)'
  as Informational RFC

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
ietf@ietf.org mailing lists by 2018-10-26. 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


  The P-Served-User header field is used to convey the identity of the
  served user and the session case that applies to this particular
  communication session and application invocation.  This document
  updates RFC5502 by defining a new P-Served-User header field
  parameter, "orig-cdiv".  The parameter conveys the session case used
  by a proxy when handling an originating session after Call Diversion
  (CDIV) services have been invoked for the served user.  This document
  also fixes the ABNF in RFC 5502 and provides more guidance for using
  the P-Served-User header field in IP networks.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-sipcore-originating-cdiv-parameter/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-sipcore-originating-cdiv-parameter/ballot/


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

This is my AD Evaluation of draft-ietf-sipcore-originating-cdiv-parameter-03.

The draft is mostly in good shape. I have a small number of substantive comments, and some editorial comments. I would like to resolve the substantive comments prior to IETF Last Call.
-------------------------------

Substantive Comments:

- Is it possible to add a short explanation of “session case”? Right now, the draft refers to 5502, but that RFC calls out to 29.228 for the definition. I think reviewers are going to find the lack of a “local” definition confusing; most will probably not drill all the way down to 29.228. I’m not asking for a lot of detail, but I think a few sentences are in order. I recognize that RFC 5502 did not do this, but I think that is a deficiency in that RFC.

§4, step 3:

Likewise, I don’t think the average non-3GPP IETF reader will understand “filter criteria” in this context. Can there be a few sentences describing it? (such as in 5502?)

§5,

- first bullet: Is the real change that the field MUST NOT contain _different_ values, or it MUST NOT contain _multiple_ values?
- 2nd bullet: It’s not clear to me what is guidance about 5502 is being offered here; this sounds more like a disclaimer about things being out of scope for this draft. Does it really belong in the bullet list?

§7, updates to the P-Served-User header field parameters:
Why do the sescase and regstate lines need to be updated to include RFCXXXX?

§9: “... it is important to ensure that the parameter has not been added to the SIP message by an unauthorized SIP entity.”

Can you say something more concrete here? How would one go about doing that? Should an AS or S-CSCF remove any cdiv parameters that it did not insert? What if a client were to insert the parameter?

Editorial Comments:

§1.2:

- Is “allocates” the correct word for assigning an S-CSCF to a user? In my mind, “allocate” connotes reserving a resource, perhaps in a way that makes it unavailable to others. Perhaps “assigns” would be better?

- 2nd paragraph:
s/ “allocated for” / “allocated to”.
s/  “HSS (Home Subscriber Server)” / “Home Subscriber Server (HSS)”
Please expand AS on first use.

§1.3:
- " first considered as a terminating session case” - Considered by what? Also, is “considered” the correct term? Perhaps something more concrete like “treated” would make more sense?

§3: " inside a Trust Domain [RFC3324] for P-Served-User header field.”
Missing article before “P-Served-User”

§4,
- step 3: " It then sends to the AS”
I suggest “sends the request to the AS”
- step 6: I suggest striking the word “specifically”

§7: The IANA considerations should either be the 2nd to last or last section. (IANA considerations and Security considerations should be the last two sections.)

As required by RFC 4858, this is the current template for the Document
Shepherd Write-Up.

Changes are expected over time. This version is dated 24 February 2012.

(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 header?

Informational, which is reflected correctly on the title page header. This document updates RFC 5502, which is also Informational. While RFC 5502 was AD sponsored, the SIPCORE WG adopted this as a working group item.

The header field P-Served-User is used only in 3GPP IMS mobile networks. Because of this, the Document Shepherd expects that during Last Call at least one person will ask why this document did not go to the Independent stream. RFC 3113 covers the 3GPP-IETF standardization collaboration. Work on SIP extensions that are needed for 3GPP networks occurs in the IETF. There was no pushback against adopting this draft in the SIPCORE working group.



(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.

Within 3GPP-specified mobile networks, the SIP header field P-Served-User [RFC5502] conveys the identity of the served user, his/her registration state, and the session case between a SIP proxy known as a Serving Call Session Control Function (S-CSCF) and a SIP Application Server (AS). Any calls that a user places (originates) or receives (terminates) pass through the user's assigned S-CSCF. Each user has a user profile that informs the S-CSCF of which action to perform depending on the session direction (originating or terminating) and the user state (registered or not). RFC 5502 covers basic originating and terminating session cases, but does not cover the case of call diversion services (CDIV) when the session is re-targeted. Without a session case for originating after CDIV, a S-CSCF cannot trigger an originating service for the diverting user nor can an AS execute the procedures for this particular session case.

This document defines a new P-Served-User header field parameter, "orig-cdiv", which conveys the session case of an originating session after CDIV services have been invoked. This document also fixes the ABNF in RFC5502 and provides more guidance for using the P-Served-User header field.



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?

This document started out in the DISPATCH working group. During discussions on list, the DISPATCH working group found issues with RFC 5502's ABNF for the P-Served-User header field, so this draft captures that feedback. While this draft was being discussed in DISPATCH, the SIPCORE charter was expanded slightly, and the DISPATCH chairs felt that this document should go SIPCORE to see if the WG wanted to take it on (originally the draft was going to go the AD-sponsored route). The WG accepted the work with lots of +1s to adopt. It received thorough feedback from a few of the participants, all of which was included.



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, 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 addition to the P-Served-User header field will be implemented in 3GPP mobile networks, so multiple vendors will be implementing this draft. 

The document's Acknowledgments section thanks reviewers who had significant feedback, and all feedback was addressed.

Since the document updates the Header Fields sub-registry of the SIP Parameters registry by adding a reference, the designated expert Adam Roach looked at it and had no issues.



Personnel

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

Document Shepherd: Jean Mahoney

Responsible Area Director: Ben Campbell



(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 IESG.

The document shepherd checked that all feedback provided on both the DISPATCH and SIPCORE lists was incorporated or otherwise addressed in document updates. This document is ready to be forwarded to the IESG.



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

No.



(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 place.

No.



(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.

The Document Shepherd has no specific concerns or issues with the draft.   



(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.

The author confirmed that she had no IPR to declare on this draft.



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

None filed.



(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? 

The draft was adopted by the working group with lots of +1s. It received thorough feedback from a handful of WG participants in both DISPATCH and SIPCORE.



(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.)

No.



(11) Identify any ID nits the Document Shepherd has found in this
document. (See https://www.ietf.org/tools/idnits/ and the Internet-Drafts
Checklist). Boilerplate checks are not enough; this check needs to be
thorough.

idnits 2.15.01 was run, and no issues were found. The Shepherd checked the draft against https://www.ietf.org/standards/ids/checklist/.  No issues were found with the draft.



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

According to RFC 5727, documents that specify Informational SIP header fields pass through an Expert Review system. Adam Roach, as designated expert for SIP header fields, reviewed the draft and had no issues with it.



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

Yes.



(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?

No.



(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 procedure.

No.



(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.

This document updates RFC 5502. This information is clearly captured in the header, abstract, and introduction.



(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 5226).

The IANA Considerations section clearly identifies the "Header Fields" sub-registry within the "Session Initiation Protocols" registry, and and shows how to modify the row in the subregistry with the new reference to this document. 

The IANA Considerations section clearly identifies the "Header Field Parameters and Parameter Values" sub-registry within the "Session Initiation Protocols" registry, and provides the values for 3 new rows in that sub-registry.



(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.

This document does not define any new IANA 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, etc.

This document corrects errata filed against the ABNF in RFC 5502 (https://www.rfc-editor.org/errata/eid4648, https://www.rfc-editor.org/errata/eid4827). The updated ABNF received feedback on the SIPCORE WG mailing list. 

Chris Newman's ABNF Validator, available at http://www.apps.ietf.org/content/tools, was run. The tool complained about undefined rules. However, those rules are defined in RFC 3261, and the document references those rules.