Indication of Support for Keep-Alive
draft-ietf-sipcore-keep-12

[Ballot comment]
Juergen Schoenwaelder spotted two editorial nits in the security considerations during his SECDIR review:

a) [...]  This specification does not specify a connection
  reuse mechanism, and it does it address security issues related to
  connection reuse.  [...]

  s/it does it/it does not/

b) [...]  They do not instruct the enity to
  place a value in a "keep" parameter of any request it forwards.  [...]

  s/enity/entity/

[Ballot comment]
I found this a clear and well-written document, thanks. I have two
smal points I would like the authors to think about, but nothing that
blocks publication.


Section 1.2

  In some cases all SIP entities that need to be able to negotiate the
  usage of keep-alives might not support SIP Outbound.  However, they
  might still support the keep-alive mechanisms defined in SIP
  Outbound, and need to be able to negotiate usage of them.

Do you actually mean...

  In some cases not all SIP entities that need to be able to negotiate
  the use of keep-alives might support SIP Outbound.  However, they
  might still support the keep-alive mechanisms defined in SIP
  Outbound, and need to be able to negotiate usage of them.

Or maybe more elegant as...

  In some cases some SIP entities that need to be able to negotiate
  the use of keep-alives might not support SIP Outbound.  However, they
  might still support the keep-alive mechanisms defined in SIP
  Outbound, and need to be able to negotiate usage of them.

[Ballot comment]
I found this a clear and well-written document, thanks. I have two
smal points I would like the authors to think about, but nothing that
blocks publication.


Section 1.2

  In some cases all SIP entities that need to be able to negotiate the
  usage of keep-alives might not support SIP Outbound.  However, they
  might still support the keep-alive mechanisms defined in SIP
  Outbound, and need to be able to negotiate usage of them.

Do you actually mean...

  In some cases not all SIP entities that need to be able to negotiate
  the use of keep-alives might support SIP Outbound.  However, they
  might still support the keep-alive mechanisms defined in SIP
  Outbound, and need to be able to negotiate usage of them.

Or maybe more elegant as...

  In some cases some SIP entities that need to be able to negotiate
  the use of keep-alives might not support SIP Outbound.  However, they
  might still support the keep-alive mechanisms defined in SIP
  Outbound, and need to be able to negotiate usage of them.

---

When can negotiation take place?

I find...

  Once a SIP entity has negotiated sending of keep-alives associated
  with a dialog towards an adjacent SIP entity, it MUST NOT insert a
  "keep" parameter in any subsequent SIP requests, associated with the
  dialog, towards that adjacent SIP entity.  Such "keep" parameter MUST
  be ignored, if received.

Which is good. And from it I deduce that if a SIP entity has not
negotiated the sending of keep-alives (either by the default of not
bothering to negotiate, or by the negotiation being rejected) it can
come back at any time and negotiate the use of keep-alives.

It may be worth saying this explcitly somewhere. (Sorry if I missed
this, but I did look.)

[Ballot comment]
I read the whole document and in general I don't have any objections to publishing it as an RFC. However I have a minor complain:

8.  Grammar

  This specification defines a new Via header field parameter, "keep".

  The ABNF [RFC5234] is:

  via-params =/ keep

  keep      = "keep" [ EQUAL 1*(DIGIT) ]

This doesn't tell me where ,  or  is defined. Please add the references as either ABNF comments or in the text before the grammar.

[Ballot comment]
This is a fine document. I have only a few comments.

1. In second paragraph of the Security Considerations, please spell out "TLS" and "DTLS" on first use and add informative references for the relevant specifications.

2. In the fourth paragraph of the Security Considerations, the specification says that a SIP entity MUST stop sending keep-alive requests if it does not receive responses to the STUN keep-alives that it sends to an adjacent downstream SIP entity. However, this does not take into account the fact that STUN requests and responses could be dropped, so it would be good to provide some more specific guidance here, e.g., stop sending STUN keep-alive requests if no STUN responses are received after sending two or more STUN requests (it seems suboptimal to stop sending STUN keep-alive requests if no response is received to only the very first STUN keep-alive request). Furthermore, no guidance is provided about the number of seconds the sender should wait before concluding that the adjacent downstream SIP entity has not responded. If these matters are covered in RFC 5389 then it would be helpful to cite the specific sections where they are discussed (e.g., Section 7.2.1 regarding retransmission timeouts).

Upon approval of this document, IANA will register the following in the
Header Field Parameters and Parameter Values registry at

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

Header Field Parameter Name Predefined Values Reference
-------------------- ------------------------- ---------- ---------
Via keep No [RFC-to-be]

State changed to In Last Call from Last Call Requested.

The following Last Call Announcement was sent out:

From: The IESG
To: IETF-Announce
CC:
Reply-To: ietf@ietf.org
Subject: Last Call:  (Indication of support for keep-alive) to Proposed Standard


The IESG has received a request from the Session Initiation Protocol Core
WG (sipcore) to consider the following document:
- 'Indication of support for keep-alive'
  as a 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 2011-01-05. 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.

The file can be obtained via
http://datatracker.ietf.org/doc/draft-ietf-sipcore-keep/

IESG discussion can be tracked via
http://datatracker.ietf.org/doc/draft-ietf-sipcore-keep/

PROTO writeup for draft-ietf-sipcore-keep-07

(1.a) Who is the Document Shepherd for this document? Has the
Document Shepherd personally reviewed this version of the
document and, in particular, does he or she believe this
version is ready for forwarding to the IESG for publication?

Adam Roach is the document shepherd. He has personally reviewed this
version of the document, and believes that it is ready for publication.

(1.b) Has the document had adequate review both from key WG members
and from key non-WG members? Does the Document Shepherd have
any concerns about the depth or breadth of the reviews that
have been performed?

The document received significant response during its
working group last-call period in SIPCORE. Prior to the
formation of SIPCORE, the document was the subject of
substantial discussion on the SIP mailing list during
the 2008-2009 time-frame. The majority of participants in
these discussions felt that the proposed mechanism provides
a useful function.

The shepherd is not aware of any extra-WG participation in
the development of this document. However, no areas have
been identified in which input from additional WGs, Areas,
or Directorates is required.

(1.c) Does the Document Shepherd have concerns that the document
needs more review from a particular or broader perspective,
e.g., security, operational complexity, someone familiar with
AAA, internationalization or XML?

The shepherd has no such concerns.

(1.d) Does the Document Shepherd have any specific concerns or
issues 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. Has an IPR disclosure related to this document
been filed? If so, please include a reference to the
disclosure and summarize the WG discussion and conclusion on
this issue.

The shepherd does not have any specific concerns regarding the
mechanism described in this document.

The shepherd is not aware of any IPR claims associated with this
mechanism.

(1.e) 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 call for adoption in SIP (as a lame duck working group) resulted
in a large number of respondents who saw a need for the mechanism
described in this document. The consensus for adoption was unanimous.

The technical aspects of the mechanism itself were worked out on the
SIPCORE mailing list among a relatively small number of key participants
(approximately four, including the author), with occasional comments
from others. The WGLC had relatively heavy participation.

(1.f) 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
entered into the ID Tracker.)

No appeal has been threatened, and no serious discontent has been
expressed.

(1.g) Has the Document Shepherd personally verified that the
document satisfies all ID nits? (See the Internet-Drafts Checklist
and http://tools.ietf.org/tools/idnits/). Boilerplate checks are
not enough; this check needs to be thorough. Has the document
met all formal review criteria it needs to, such as the MIB
Doctor, media type and URI type reviews?

The document passes both the ID Nits tool and a manual inspection.

(1.h) Has the document split its references into normative and
informative? 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
strategy for their completion? Are there normative references
that are downward references, as described in [RFC3967]? If
so, list these downward references to support the Area
Director in the Last Call procedure for them [RFC3967].

References are split. All references are RFCs. All normative
references are standards-track (except RFC 2119), so no downrefs
exist.

(1.i) Has the Document Shepherd verified that the document IANA
consideration section exists and is consistent with the body
of the document? If the document specifies protocol
extensions, are reservations requested in appropriate IANA
registries? Are the IANA registries clearly identified? If
the document creates a new registry, does it define the
proposed initial contents of the registry and an allocation
procedure for future registrations? Does it suggest a
reasonable name for the new registry? See [RFC5226]. If the
document describes an Expert Review process has Shepherd
conferred with the Responsible Area Director so that the IESG
can appoint the needed Expert during the IESG Evaluation?

The document adds a parameter to an existing IANA registry.
The registry is clearly identified, and the new entry is
in a format that matches the IANA table.

(1.j) Has the Document Shepherd verified that sections of the
document that are written in a formal language, such as XML
code, BNF rules, MIB definitions, etc., validate correctly in
an automated checker?

The only formal language present is an ABNF definition. The
definition, which is reproduced below in its entirety, is
correct by casual inspection:

via-params =/ keep
keep = "keep" [ EQUAL 1*(DIGIT) ]


(1.k) 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 defines a mechanism by which adjacent
SIP entities can negotiate the use of the NAT keep-alive
mechanism defined in RFC 5626, even if the other
mechanisms described in RFC 5626 are not being applied.

Working Group Summary

The document was largely without controversy during its
lifetime. Early in the discussion of the mechanism
(in the SIP working group), several people challenged
the utility of a mechanism for negotiating this kind of
behavior (as opposed to simply sending keep-alives
unilaterally). Ultimately, the working group decided
that the chances for things "going wrong" under those
circumstances were too great, and elected to define
an explicit negotiation mechanism.

Document Quality

Several implementors and network operators have indicated that
the have need of and plan to implement the mechanism described
in this document. It is not known whether any implementations
of the mechanism exist.