Subject: RE: [Sip] SIPIT Interop problem with ;user=phone

From: "Francois Audet" <[email-masked]>
Date: Fri, 12 Sep 2003 17:53:55 -0700

> For a dial string of 1234, either:
> 	tel:1234;phone-context=your-dialplan.foo.bar
>    or
> 	sip:[email-masked];user=phone

Your sip URI has the problem that you need one DNS entry for each 
dialling plan. If an Enterprise has different dialling plan per
region (like they do), then the dialplan-knowledgeable proxy needs
to figure out which dialling plan should apply based on 
some criteria such as the source of the original message or black 
magic, correlated with some database. This is pretty messy.

Also, it still seems to me that the "user=phone" is taken by most 
people to mean that the SIP URI is constructed from a tel URI using
the RFC3261/19.1.6.

Applying the rules of RFC3261/19.1.6 instead, we'd get:

	sip:1234;phone-context=[email-masked];user=phone

Which (like the tel URI) specifically identifies the dialing plan and does
not require one DNS entry per dialling plan.

---

From: Paul Kyzivat <[email-masked]>
Date: Mon, 15 Sep 2003 09:58:22 -0400

Francois Audet wrote:
> dialling plan.

I agree. The answer to this is "if it hurts, don't do it".

In other words, I think that approach only makes sense when the 
dialplans line up with the proxies you are willing to configure.

 > If an Enterprise has different dialling plan per

Again I agree. The whole point here is to ensure that the url itself is 
context-free. In my opinion, if the proxy needs to apply context from 
other parts of the message in order to expand the number, then this is 
an invalid usage.

> people to mean that the SIP URI is constructed from a tel URI using

I'm not sure about the "most" part. Some do, some don't. As spec is 
currently written, the equivalence between tel and sip/user=phone is 
only one way. (IF the userpart comes from a tel, then there SHOULD be a 
user=phone, but the presence of user=phone does not imply the userpart 
conforms to tel.)

I personally am happy with the more strict interpretation. But I am 
trying to hold out an olive branch in order to reach a level of agreement.

> not require one DNS entry per dialling plan.

I agree that this is also a fine usage.

But what is benefit of this over using the tel format and then passing 
the request to sip:foo.bar?

	Paul

_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip