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Re: [Simple] tel URIs in common policy

Brian,

Brian Rosen wrote: 
Paul

Not sure yet what I think of the basic idea, but
   sip:+1-232-1234 at foo.com;user=phone
should be equivalent to
   tel:+1-232-1234

Well, I am suggesting that, when the purpose is identifying a caller for purposes of authorization.

According to 3261, only someone responsible for the foo.com domain can decide that these are equivalent. If you are not responsible for that domain then you are not permitted to conclude they are equivalent. So I am in some sense advocating violating 3261 in this case.

Unless we plan to change 3261, or look the other way while people violate it, this is a fundamental problem with using sip;user=phone address forms.

So I think you CAN convert it to "enum" form.

According to sip routing rules, if you are not responsible for the foo.com domain, you *definitely* can't do this to route the sip address! You must simply route it based on the domain name.

I see this as a key difference between the two forms. With the tel form, anybody can just go to the PSTN, or use enum to find possible ways of reaching it. With the sip form, you can only reach the address via sip.

You might have more problems with
   sip:1234 at foo.com

That may be equivalent to
   tel:1234;phone-context=foo.com
but you don't know that a priori.

There is certainly nothing written down anywhere that would lead you to believe you could do that. If it can be done, it is only on a domain-specific basis, and so can only be done by someone responsible for the domain.

	Paul

Brian

-----Original Message-----
From: simple-bounces at ietf.org [mailto:simple-bounces at ietf.org] On Behalf Of
Paul Kyzivat
Sent: Wednesday, August 10, 2005 2:19 PM
To: Aki Niemi
Cc: simple at ietf.org; ext Henning Schulzrinne
Subject: Re: [Simple] tel URIs in common policy

Aki,



Aki Niemi wrote:

Hi,

I kind of grew fond of the idea Cullen and I came up with in a private conversation, namely treating telephone numbers as domains similar to when issuing a DNS ENUM query.

In essence, to match +1-232-555-1234, you'd have an identity conditions such as:

<many domain="4.3.2.1.5.5.5.2.3.2.1.e164.arpa" /> 


Then what do you do with sip:+1-232-555-1234 at foo.com;user=phone ?

I don't think you can convert it to:

    4.3.2.1.5.5.5.2.3.2.1.foo.com

and if you could then it it wouldn't match the e164.arpa form.


This has an interesting additional property of being able to match based on country code, area code, etc. For example, to match all Finnish telephone numbers, you'd have:

<many domain="8.5.3.e164.arpa" />


It only does if you declare that a domain matches anything it is the tail of. You may sometimes want that, but I don't think you do in general.

	Paul


Not being an expert on ENUM or E.164 in general, I suspect this is horribly broken, but it pleases the aesthethic eye.

Cheers,
Aki

ext Henning Schulzrinne wrote:


In a side conversation, Hannes suggested a solution to the tel URI problem we discussed during the WG meeting, akin to what's done in the geopriv coordinate system parameter, namely to have a parameter that identifies the scheme, as in

<one scheme="tel" id="+1-212-555-1234"/>

or

<one scheme="sip" id="alice at example.com"/>

if you really only want to match SIP identity sip:alice at example.com.

The default with no scheme parameter is "matches any user at domain scheme".

In order to complete finishing the section of the spec, I'd value quick feedback on the idea.

Henning

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