Subject: Re: [Iptel] Summary of +1-800 for tel URI discussion

From: Michael Hammer <[email-masked]>
Date: Mon, 02 Dec 2002 09:41:24 -0500

All,

I suspect that the routing of the call to multiple destinations, even 
though the same 1-800 number is used, has nothing to do with the 1-800 
number and everything to do with other information contained in the 
signaling, and thus very much orthogonal.  If sticking this other 
information into the tel: URL is the way independent information is bound 
to a phone number, so be it; but, then there are many pieces of information 
that could be bound in such fashion.

Mike

At 03:09 PM 11/30/2002 -0500, Henning Schulzrinne wrote:
>Scott,
>
>trying to guess at the source of confusion here. I suspect that part of 
>the problem might be two meanings of the word 'context':
>
>- Context = 'resolve this identifier under this context' 
>(;context=+1-212-939-7000 = Pizza Hut as if dialed from 212-939-7000)
>
>- Context = 'this number is only valid if dialed from this context; it's 
>an error otherwise' (the number may still reach something or other, but 
>it's not the intended destination)
>
>I think most of us are thinking of the second use, not the first. Your 
>paragraph seems to hint at the first. Thus, for PizzaHut, there would be 
>no need for context (the number is valid, albeit routed differently 
>everywhere in the +1 context.) The problem I have with the first 
>interpretation is that the context is unknown, since the routing can 
>depend on any prefix and can never be known by the writer of a web page, say.
>
>I suspect that the PizzaHut routing problem is basically unsolvable as 
>soon as you have gateways; you'll always reach the PizzaHut closest to the 
>gateway, not the IP-based caller. The routing algorithm is presumably 
>based on more than just digits in the ANI phone number. The problem is 
>essentially the same as the 911 routing problem; maybe Intrado can start a 
>new line of business :-)
>
>However, I'm still not sure I understand your concern.
>
>Now, do I get a PizzaHut coupon?
>
>Scott Bradner wrote:
>
>> >I really do not want extra language in the spec to handle what I suspect
>> >is a non-issue, because if folks don't know any better they will litter
>> >all freephone numbers with context which in most cases is not only
>> >extraneous, but also in some cases harmful to proper routing.
>>
>>
>>I guess I must be confused about this issue - I would have thought that
>>one needed locational context to resolve 1-800-hot-pizza (or
>>whatever dominos country-wide number is) in order to direct a call
>>to the right place (one on N-thousand local shops)
>>
>>it would seem to be a database loading issue if that number gets paid for
>>by one or more organizations and not an issue of what information you
>>need to get to the right place
>>
>>Scott
>
>
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---

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 03 Dec 2002 03:00:12 -0500

> (;context=+1-212-939-7000 = Pizza Hut as if dialed from 212-939-7000)

I believe this is out of scope. We are not trying to direct routing.

> it's not the intended destination)

This is what I believe we are talking about.

I thought I heard someone suggest another usage during the meeting, to 
support things like VPNs:

- Context: this number can only be interpreted by first routing the call 
to this context, and the interpreting it there

For example, if a company has a PBX without DID, and its number is 973 
555 1234, I would reach extension 33 this way:

tel:33;context="+19735551234"

THis is similar in concept to relative URI references.

I don't think this is in scope either, and so perhaps I misinterpreted 
what was said during the iptel meeting. If someone does think we are 
supporting this, please speak up.

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com

---

From: Scott Bradner <[email-masked]>
Date: Tue, 3 Dec 2002 07:09:04 -0500 (EST)

> to this context, and the interpreting it there

not sure that is enough if the context is geographic since the
"first routing node" may be half the world away

Scott

---

From: Henning Schulzrinne <[email-masked]>
Date: Tue, 03 Dec 2002 08:08:53 -0500

The context is meant to lead to a binary decision: Either you know 
you're in the context or you know you're not. Each node knows its 
context (a set of E.164-style numbers or a domain name) and simply 
checks if the tel URI context matches one of them, exactly.

Again, based on the discussion, this is not useful or necessary for 800 
numbers or service routing - this is effectively to prevent a PBX 
extension that 'escaped' its context to be used somewhere out of scope 
(a Harvard extension within Columbia, say, or the internal 
Belgian/Japanese NNI service number that a few people mentioned).

Any geographic scope should be in something like caller preferences.

---

From: Henning Schulzrinne <[email-masked]>
Date: Tue, 03 Dec 2002 08:32:56 -0500

> I believe this is out of scope. We are not trying to direct routing.

I hope not.

>
>
> >
> > - Context = 'this number is only valid if dialed from this context;
> > it's an error otherwise' (the number may still reach something or
> > other, but it's not the intended destination)
>
>

At least that's what I've been trying to get at :-)

> supporting this, please speak up.

At least in the past, we've explicitly ruled this out since the context 
is insufficient to get to that destination. (This is particularly true 
for domain names.)

 From what I can tell, anything but a simple binary decision answering 
"can I process this URI" is going to be too brittle for use or too 
constrained in its functionality.

---

From: Flemming Andreasen <[email-masked]>
Date: Tue, 03 Dec 2002 17:41:53 -0500

> support things like VPNs:

Right. I was considering things like private numbering plans/VPNs, where you
within a single provider network (or cooperating providers) can pass private
numbers around without requiring translation to public E.164 numbers. However,
you also need to pass a "VPN Group ID" in order to ensure proper
interpretation and further routing at the next hop. In essence, a context.

> THis is similar in concept to relative URI references.

I was only referring to private numbering plans.

> supporting this, please speak up.

I do believe we should support private numbering plans and something like
context seems useful for that.

-- Flemming