Subject: Re: AW: [Iptel] comments on rfc2806bis - 800 numbers

From: [email-masked]
Date: Wed, 20 Nov 2002 13:31:06 EST

There have been several comments related to the format/use of freephone 
(e.g., 800) numbers in the tel:uri.

In a message dated 11/19/2002 8:39:53 PM Eastern Standard Time, 
[email-masked] writes:

> As stated below, an national 800 number is always part of the E.164 
> numbering plan. Depending
> on the accounting agreements between national operators, you may reach the 
> 800 numbers in another country or not. If not, on the PSTN you are routed 
> to an announcement.
> 
> So if yes, you may use e.g. tel:+1800xxx for an NANP 800 number, if not, 
> you may indicate
> this with tel:800xxx,phonecontext=+1
> 
In a message dated 11/19/2002 9:03:39 PM Eastern Standard Time, 
[email-masked] writes:

> It may work sometimes, but not always. For example, a number may be valid in
> the US but not in Canada (this is very common, perhaps even the most common
> case). 
> These countries however both share the same +1 country code. 
> 
> I guess one could argue that the area code of the originator could be listed
> as phone-context
> (phone-context=+1-408). The proxy would have to figure out that 408 is part
> of the US not
> Canada, and if it is valid or not for this 1-800 number (it would be
> impractical to list
> ALL the area codes where the 1-800 is valid). 
> 
> Another alternative would be a phone-context describing differently the
> applicability 
> domain (something.ca or something.us).
> 
In a message dated 11/19/2002 8:59:19 PM Eastern Standard Time, 
[email-masked] writes:

> the unfortunate fact that E.164 numbers in the +1-800 domain cannot be 
> successfully reached from anywhere does not in any way affect their 
> validity as global tel: URL numbers.
> 

[MAP] I think one needs to look at the intended use of this tel:uri. I think 
of the best example (certainly one of the valid ones) is that the tel:uri is 
the real information to dial a call that is "behind" a link on a web page. In 
this case, anyone anywhere in the world may try to place a call by clicking 
on this link. Therefore, the contents/format of the tel:uri should not depend 
on whether or not your local national agreements allows the call to be made. 
The format needs to be one single global format (E.164-type format works 
well) and the local user agent/device needs to be able to figure out from the 
information in the tel:uri as well as knowledge of where it is to decide 
whether or not the call can be made (or even how to make it).

The fact that an 800 number can be represented as an E.164 number is not 
unfortunate - I think it is a big help here.

I suggest that the rule is that any number that can be represented in the 
E.164 format MUST be done this way. (A slight strengthening/clarification of 
the current text.) This means that an "800" number would never have a context 
included, just as no other E.164 number needs one. This removes some of the 
difficulties with the current definition.

What I would really expect on a simple web page is something like the 
following:

If in Germany, click here (the tel:uri behind it contains Germany country 
code and the 800 number)
If in Austria, click here (the tel:uri behind it contains Austria country 
code and the 800 number)
If in Italy click here (the tel:uri behind it contains Italy country code and 
the 800 number)
If in Maryland, click here
etc.

If the 800 numbers in multiple places happen to be the same string of 
numbers, that is not important.)

Clicking on the wrong link for the location would simply result in a call 
failing, just as if you read off the wrong number from a list and dialed it 
on your PSTN phone.

On the other hand, a more complex web page/user agent may include logic (Java 
Script?) to provide a single point to click, and the user agent/device would 
know where it is (within the numbering plans) or the user would have told it 
and the UA would figure out which one of many internal numbers to use to 
place the call. Each of these internal numbers would be in the form of a 
tel:uri.

Mike Pierce
Artel

---

From: Henning Schulzrinne <[email-masked]>
Date: Thu, 21 Nov 2002 16:38:18 -0500

M. Pierce wrote:

> [MAP] I think one needs to look at the intended use of this tel:uri. I 
> think of the best example (certainly one of the valid ones) is that the 
> tel:uri is the real information to dial a call that is "behind" a link 
> on a web page. In this case, anyone anywhere in the world may try to 
> place a call by clicking on this link. Therefore, the contents/format of 
> the tel:uri should not depend on whether or not your local national 
> agreements allows the call to be made. The format needs to be one single 
> global format (E.164-type format works well) and the local user 
> agent/device needs to be able to figure out from the information in the 
> tel:uri as well as knowledge of where it is to decide whether or not the 
> call can be made (or even how to make it).
> 
> I suggest that the rule is that any number that can be represented in 
> the E.164 format MUST be done this way. (A slight 
> strengthening/clarification of the current text.) This means that an 
> "800" number would never have a context included, just as no other E.164 
> number needs one. This removes some of the difficulties with the current 
> definition.

I think treating tel URIs consistently as identifiers ("URN") helps 
conceptually. After all, if I specify an ISBN number (another URN), it 
is globally unique, but there is no guarantee that my local book store 
can order the book or that the library carries it.

Similarly, there are any number of reasons that a non-800 E.164 number 
can fail: administrative prohibition, number disconnected, invalid 
number, local outbound call filtering, etc.

Thus, the important consideration is only "is this number unique without 
a context"? Thus, a context would be needed if +1-800-something refers 
to two logically different entities in Canada and the US. (Obviously, an 
800 number may end up in many different locations depending on the 
source of the call, but that's not the problem.) I don't know if that's 
possible. To put it more concretely: will the same 800# ever be assigned 
to two different entities, as in

1-800-123-4567 reaches PizzaHut if dialed in New York
and
1-800-123-4567 reaches Domino's if dialed in New Jersey
and
1-800-123-4567 reaches WeightWatchers if dialed in Canada

> On the other hand, a more complex web page/user agent may include logic 
> (Java Script?) to provide a single point to click, and the user 
> agent/device would know where it is (within the numbering plans) or the 
> user would have told it and the UA would figure out which one of many 
> internal numbers to use to place the call. Each of these internal 
> numbers would be in the form of a tel:uri.

We need a DHCP option that conveys the local area code! (Sorry, inside 
joke for the Geopriv crowd.)

> Artel

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