Locating Session Initiation Protocol (SIP) Servers in a Dual-Stack IP Network
draft-ietf-sipcore-dns-dual-stack-08

[Ballot discuss]
* Section 3.1

It is not clear to me what exactly the normative addendum is requiring the client to do as regards to the DNS query while implementing "The dual-stack client SHOULD look up all address records". Does this mean that the client should do a AAAA (28) query followed by (or in parallel or preceded ) for a A (1) query? I think it would be good to clarify the types and ordering/concurrency of the queries.

* Section 4

I am a bit puzzled by the merging of the address lists from two separate DNS queries in relation to RFC6724. This is how I see the destination address selection in RFC6724. The application ends up calling some kind of name resolution API (something like getaddrinfo()) with a hostname/FQDN (say sip-1.example.com) and this results in a set of addresses being returned. The destination address selection algorithm specified in Section 6 of RFC6724 then orders these addresses and picks one. I am not seeing how the second FQDN and its associated set of addresses become involved in the RFC6724 process. Is this something that you are adding on top of RFC6724? Please clarify.

[Ballot comment]
I appreciate this work. I do have one comment.

Could you provide some explanation for the reader as to why SIP is "different", following this statement? Even an example would be useful.

  Unfortunately, in common SIP situations, it is not possible to "race"
  simultaneous request attempts using two address families.

[Ballot comment]
Thanks! This seems very useful in the preparation for Happy-Eyeballs.

One question: Why does a client need to look up ALL addresses if it already knows that it itself only support one specific address familiy?

And related to this question: Shouldn't it be named "multi-stack client" instead of "dual-stack client"?

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

IANA has reviewed draft-ietf-sipcore-dns-dual-stack-06.txt, which is currently in Last Call, and has the following comments:

We understand that this document doesn't require any IANA actions.

While it's often helpful for a document's IANA Considerations section to remain in place upon publication even if there are no actions, if the authors strongly prefer to remove it, IANA does not object.

If this assessment is not accurate, please respond as soon as possible.

Thank you,

Sabrina Tanamal
IANA Specialist
ICANN

The following Last Call announcement was sent out:

From: The IESG
To: "IETF-Announce"
CC: ben@nostrum.com, adam@nostrum.com, sipcore-chairs@ietf.org, sipcore@ietf.org, "Adam Roach" , draft-ietf-sipcore-dns-dual-stack@ietf.org
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (Locating Session Initiation Protocol (SIP) Servers in a Dual-Stack IP Network) to Proposed Standard


The IESG has received a request from the Session Initiation Protocol Core
WG (sipcore) to consider the following document:
- 'Locating Session Initiation Protocol (SIP) Servers in a Dual-Stack IP
  Network'
  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
ietf@ietf.org mailing lists by 2016-07-04. 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


  RFC 3263 defines how a Session Initiation Protocol (SIP)
  implementation, given a SIP Uniform Resource Identifier (URI), should
  locate the next-hop SIP server using Domain Name System (DNS)
  procedures.  As SIP networks increasingly transition from IPv4-only
  to dual-stack, a quality user experience must be ensured for dual-
  stack SIP implementations.  This document updates the DNS procedures
  described in RFC 3263 for dual-stack SIP implementations in
  preparation for forthcoming specifications for applying Happy
  Eyeballs principles to SIP.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-sipcore-dns-dual-stack/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-sipcore-dns-dual-stack/ballot/


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

This is my AD evaluation of draft-ietf-sipcore-dns-dual-stack-06. I only have a few editorial comments. None of these need to delay IETF last call, and can be handled along with any feedback from the last call.
---------
-1, 2nd paragraph, first sentence:

That sentence is a bit hard to parse, please consider breaking into two or more simpler sentences.

-2, definition of IPv4/IPv6 UA/UAC/UAS:

This defines one term, then declares the draft will use another. Why not just define _that_ term in the first place?

-4:

This section kind of buries the lede, and leaves me wondering what the actual clarification was. Is the point to say not to interleave the results of the address record queries among srv records? Is there a concern that people thought they were to do something different? It would be helpful to say what misconception you intend to clarify.

-5, first paragraph, last sentence:

Oddly constructed sentence. The structure seems to imply a tension between the idea of optimizing performance and not introducing security considerations. Please consider something to the effect of the following:

“Both of these procedures are optimization designed to improve the performance of dual-stack clients. Neither introduce new security considerations.”

(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?

  Proposed standard. This type is selected due to the normative changes to RFC
  3263, which is a standards-track document. The draft header indicates that
  it is standards-track.

(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

  This document lays the groundwork for future "Happy Eyeballs"-style
  work on SIP by updating DNS procedures for SIP URI resolution rules
  in a way that clarifies behavior for SIP stacks that support both
  IPv4 and IPv6.

Working Group Summary

  The document spent several years in the working group, with
  occasional bursts of activity. The final push to completion
  was performed over the past few months by a concerted effort of a new
  author, who both incorporated long-standing feedback from the working group
  and worked out some of the finer details of the document. No aspect of
  the discussion proved controversial.

Document Quality

  The document received in-depth review from a small handful of
  working group participants, and the results of those reviews
  were incorporated into the final version. No implementations
  of the protocol described in the document are known to exist yet;
  however, some of the problems addressed by the draft have been
  concretely demonstrated at the SIPit 31 interop event (which also
  highlighted some previously unnoticed problems with dual-stack
  address resolution). Dan Wing provided expert review for interaction
  with "Happy Eyeballs" techniques.

Personnel

  Adam Roach is the document shepherd. Ben Campbell is the
  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 IESG.

  The document is short, and its scope is relatively narrow. The
  shepherd has read through the final version of the draft for
  coherence and technical soundness. Aside from some editorial
  nits that should be caught by the RFC editor, the document is
  in good shape.

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

  While working group feedback was decidedly low-key, the procedure revisions
  described in this document are somewhat arcane. The number of participants and
  level of activity was approximately as expected.

(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.

  This document clarifies and updates DNS procedures for SIP server address
  resolution, in preparation for follow-on "Happy Eyeballs for SIP" work. Dan
  Wing provided an expert review (via email) of the document from this angle.
  The result of his review was posted to the SIPCORE list:
 

(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 shepherd has no concerns about the document.

(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.

  Each author has confirmed conformance with BCPs 78 and 79.

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

  No disclosure has been 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?

  There were only a few WG participants who were involved with the
  discussion of this document (on the order of 10 or so, over its
  lifetime).

(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.

  The document passes both automated checks and a manual examination
  against the nits checklist.

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

  No such formal reviews are applicable.

(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 normative downrefrefs are present.

(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.

  The document's sole purpose is to  normatively update the procedures in
  RFC 3263. This is spelled out in the abstract, introduction, and throughout
  the rest of the document.

(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 section is appropriately empty.

(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 requires no actions of IANA.

(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.

  The document contains no formal languages to validate.