Subject: Last Call: SIP: Session Initiation Protocol to Proposed Standard

From: The IESG <[email-masked]>
Date: Mon, 28 Sep 1998 07:50:22 -0400

The IESG has received a request from the Multiparty Multimedia Session
Control Working Group to consider SIP: Session Initiation Protocol
<draft-ietf-mmusic-sip-09.txt> 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 any comments to the
[email-masked] or [email-masked] mailing lists by October 12, 1998.

Files can be obtained via
ftp://ftp.ietf.org/internet-drafts/draft-ietf-mmusic-sip-09.txt

---

From: Eliot Lear <[email-masked]>
Date: Mon, 28 Sep 1998 09:05:18 -0700

I've previously raised this objection with the Author.

I draw your attention to section 1.4.2 of draft-ietf-mmusic-sip-09.txt.

SIP makes use of MX records.  SIP has nothing more to do with the EMail
infrastructure than any other application protocol.  If we need another
record we should use another record.  Overloading MX records may lead to
unforeseen oddities with random packets flowing to places not expecting
them, or even blocking them, causing long delays in call setup.

SIP (properly IMHO) refers to SRV records, except that I am now given to
understand that the existing RFC on SRV needs minor fixing that will
impact SIP.  I personally woulr rather not speak to the SRV problems. 
Perhaps Paul Vixie or Jerry Sharf might wish to elaborate (something
about underscores?).

It would be good if SRV could get fixed quick and advanced and SIP
merely delete references to MX.  In the short term, perhaps use a web
like solution, such as sip.{domain} and A records.  If MX records are to
be used in the short term, the document should at the very least
indicate their impending obsolescence for this purpose.
-- 
Eliot Lear
[email-masked]

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From: Henning Schulzrinne <[email-masked]>
Date: Mon, 28 Sep 1998 14:01:50 -0400

> indicate their impending obsolescence for this purpose.

There was recent discussion (as in, this weekend) on this topic on this
mailing list, with various arguments for and against.

MX was always intended as a stop-gap measure until SRV records are a
realistic alternative. We are currently investigating the support that
SRV enjoys in various common OS, both from a client and server
perspective, to help SIP software authors to support them in their
offerings. Initial indications are that SRV will be supported in NT 5.0
DNS servers (to support LDAP) and is supported in recent version of
bind. They are not supported in resparse-1.3, although I've made the
necessary changes (and others may have independently done the same). The
status of DNS lookup functions in Perl, Tcl and Java is being
investigated; any insight would be most helpful here. (I'll be gathering
related information on the SIP web page.)

As far as I know, only one SIP implementation supports SRV records,
although a second one has promised support.

Given the amount of controversy that it generates compared to its
perceived value, the SIP authors agreed that the most expedient solution
would be the removal of MX from the SIP spec.

A related question is whether, as a short-term measure until SRV is
widely deployed, client authors should given the hint (it clearly can't
be more than that) to try [email-masked] when address
[email-masked]' is being entered. This is similar to the convention 

I would want to avoid establishing [email-masked]' as the
published address since it defeats the point of allowing users to limit
the number of different addresses for different means of communication.

Using A records works in some cases where 'domain.com' is also a valid A
address. However, it suffers some of the same problems identified with
MX records, in that if the mail host moves, it will likely take the
'domain.com' host name with it.

-- 
Henning Schulzrinne   [email-masked]
Dept. of Comp. Sci.   ph  +1 212 939-7042
Columbia University   fax +1 212 666-0140
New York, NY 10027    http://www.cs.columbia.edu/~hgs

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From: Eliot Lear <[email-masked]>
Date: Mon, 28 Sep 1998 11:12:23 -0700

Henning Schulzrinne's response satisfies my objections, in as much as an
updated draft will reflect those changes.
--
Eliot Lear
[email-masked]

---

From: Paul A Vixie <[email-masked]>
Date: Mon, 28 Sep 1998 11:47:59 -0700

RFC2052bis was sent to namedroppers during the week of the Chicago IETF.
(I sent it from the WaveLAN area near the bar.)  I don't know how to get
it advanced any quicker -- Microsoft had an objection but dropped it.