Subject: [Geopriv] Re: [Simple] tel URIs in common policy

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 16 Aug 2005 20:39:06 -0400

cc'ing geopriv since all of this is about a geopriv document.

I'll reply to some of the technical comments inline, but I want to step 
back a second here.

All of this discussion is making it clear that there is a MUCH bigger 
mess here that needs attention, around phone number usage, 
interpretation and equivalence across tel and SIP URI. This is a common 
source of interop problems in the wild and it makes sense to address it. 
However, the problem at hand is to complete the common policy document, 
and it seems to me a mistake to hold up common policy until that mess is 
sorted out. Furthermore, I would argue that the common policy spec is 
not the place where that mess should be sorted out.

My suggestion therefore is to keep the "id" attribute as an NAI form, 
and make sure common policy is extensible to allow other ways of 
representing identities in the future. We then declare phone numbers out 
of scope for this version of common policy, finish that spec, sort out 
the tel/sip uri mess, and when thats done, we can issue an extension to 
common policy that adds phone number support.

more inline.

Paul Kyzivat wrote:

> 
> 
> Aki Niemi wrote:
> 
>> Hi Paul,
>>
>> ext Paul Kyzivat wrote:
>>
>>> Then what do you do with sip:[email-masked];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.
>>
>>
>>
>> Well, 'sip:[email-masked];user=phone' is indeed a tricky 
>> identity to put into a From header in the first place. I'm not sure it 
>> is a telephone number at all. Why wouldn't the From include a tel URL?
> 
> 
> Personally, I generally think it should. However I have run into many 
> people who don't seem to believe in tel URIs, and always use the sip 
> form. I would like to convince them of the error in their ways, but no 
> luck so far.

I think the problem is that we've not made it clear what the semantic 
differences really are.

> 
> The other case is when I really, definitely, only want to be contacted 
> via SIP.
> 
>> I suppose that matching a SIP URI converted from a tel URL will be a 
>> problem regardless of the way in which we choose to represent them in 
>> common policy.
> 
> 
> I am relaxing my theoretical objections in favor of pragmatism, and 
> suggesting that for purposes of determining what authorization policy to 
> apply it will be ok to treat this as a phone number.

Stepping back for a sec, I think there are real differences between the 
tel URI and the sip version. The way to think about it is that the tel 
URI is a NAME, and you need to think of it as if it were a URN. A SIP 
URI is an address. Procedures like enum allow the resolution of a name 
to an address.

As such, it really makes no sense to compare a name and an address. Just 
because I work at 600 Lanidex Plaza in Parsippany, does that make 
"Jonathan Rosenberg" (a name) equivalent to "600 Lanidex Plaza, 
Parsippany, NJ 07054"? Definitely not. So, I would argue that the tel 
URI and SIP URL are NEVER equivalent; you need to convert the name to an 
address for comparison.

Givne this, the meaning of sip:<phone-number>@domain;user=phone means 
that the domain is asserting ownership of the identity in the user part, 
in this case a global phone number. As such, its appropriate to use this 
form only when it is authoritatively known that the domain in question 
"owns" that phone number.

-Jonathan R.
-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Director, Service Provider VoIP Architecture   Parsippany, NJ 07054-2711
Cisco Systems
[email-masked]                              FAX:   (973) 952-5050
http://www.jdrosen.net                         PHONE: (973) 952-5000
http://www.cisco.com

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---

From: Paul Kyzivat <[email-masked]>
Date: Thu, 18 Aug 2005 17:41:11 -0400

Jonathan Rosenberg wrote:

>> suggesting that for purposes of determining what authorization policy 
>> to apply it will be ok to treat this as a phone number.
> 

As far as general comparisons are concerned, I agree with you.
But I don't think matching caller "identity" for purposes of 
authorization need be viewed as a general URI comparison problem.

I don't have a lot of control over the way people identify themselves 
when they call me. Somehow I must recognize their identifications of 
themselves in a way that is sufficient for my needs. If I need to do 
funky huristic comparisons to achieve that, so be it.

It is for this reason that I think we can do special things here. We 
know the identification of the caller will be some form of URI. The ones 
if interest here are sip, sips, tel. The values we put into the policy 
don't need to be URIs - practically speaking they are patterns to be 
matched against caller identification. URIs, using URI comparision are 
one form of pattern match. But we can define something looser - either 
the matching algorithm can be different/looser, and/or the pattern 
itself can be different/looser.

What I am proposing is both: patterns that are a superset of valid URIs, 
and a matching algorithm that is similar to but looser than just pattern 
matching. In particular:

- a pattern containing a tel uri would be matched against sip and sips 
uris with user=phone by simply comparing the user parts using tel 
matching rules.

- perhaps allowing a wildcard character in a "tel" pattern - e.g. an "n" 
instead of a digit. Match by ignoring corresponding character in target.

Of course it wouldn't be necessary to use something that looked like tel 
format to represent this. We could make up some other format that was 
clearly specific to the use at hand. Semantically it wouldn't make any 
difference.

Similarly, I think there is an need for a way to say: match either a sip 
or sips uri. That of course is just syntactic sugar, but I doubt people 
will be happy having to include every target twice, so it is probably 
important.

	Paul

---

From: Paul Kyzivat <[email-masked]>
Date: Thu, 18 Aug 2005 20:05:34 -0400

Jonathan Rosenberg wrote:

>>> identity to put into a From header in the first place. I'm not sure 
>>> it is a telephone number at all. Why wouldn't the From include a tel 
>>> URL?
>>

I'd like to think that is the case. But it is so pervasive I suspect 
there are multiple world views, or religions, here.

> "owns" that phone number.

*I* could potentially agree with that, but it seems most people don't.

In general, I think all the above means is that the domain in question 
is accepting responsibility for getting the request wherever it goes. It 
might not own the phone number, in which case it may use peering or a 
pstn gateway to get to the right place.

It seems very popular for a UA to construct such a URI, with the domain 
of its service provider, to ask the service provider to get this to the 
right place.

I think that is entirely wrong, but it seems we have 80% of the world to 
convince of that.

	Paul