Subject: [Speermint] use of RFC 3263 for locating peer's SIP server

From: "Jean-Francois Mule" <[email-masked]>
Date: Mon, 19 Jun 2006 09:04:08 -0600

Hi,

   We have discussed the use of the DNS procedures specified in RFC3263
in speermint to resolve a SIP URI into a reachable host (IP address and
port), and transport protocol.

   To document the best current practices, could you contact me if you
have any implementation or operational experience in field use of 3263
mechanisms (full 3263 or partial NAPTR/SRV)?
	- based on Robert Sparks' presentation in IETF#65 SIPPING on the
status of the implementation in sip interoperability testing events:
	40% of implementers showing up in SIPit do NAPTR, 
	50% do SRV.

	- when implemented on the products, how many folks use those
options? any feedback on the field use of 3263 for NAPTR lookup for SIP
transport protocol selection?
a) The RFC indicates that if the URI contains the transport protocol,
then it should be used (no lookup): is this common? Should it be?
b) In a few publicly-available product administration guides I have
looked at, NAPTR lookup for transport selection can be turned on/off
when it exists as anyone would expect. Do service providers use it? If
no, what are the issues?
==> I'm told that some service providers mandate one transport protocol
(say TCP) for SIP termination and therefore, the transport protocol to
reach a peering partner is often statically configured along with the
sip route. Is this common?
===> some folks believe it is costly to do on a per query basis. Is this
a matter of recommending proper DNS caching and long enough TTL values
for those things?

	- what about SRV? Same questions.

If I get enough feedback, my goal is to provide a brief summary on the
above to the list, and possibly, draft one or two slides outline any
issues at IETF#66.

Thanks,
Jean-Francois.

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From: "Rohan Mahy" <[email-masked]>
Date: Mon, 19 Jun 2006 14:05:17 -0700

Hi Jean-Francois,

To use full NAPTR and SRV lookups in a peering context, we are only
really worried about a pair of SIP proxies (one for the initiating
peer and another for the receiving peer) implementing NAPTR.  Note
that most of these proxies will be consulting ENUM records and will
need to implement NAPTR anyway for ENUM.  I don't think RFC3263 is too
much to ask for.

thanks,
-rohan