Subject: Re: URL Generalization for Portability (was TRIP)

From: "Adam B. Roach" <[email-masked]>
Date: Tue, 4 Jan 2000 13:49:40 -0600 (CST)

>I'm honestly queasy about this. One of things IP did right was to make
>its addresses and domain names always well defined independent of where
>you are located. With IP addresses, we never send just the last byte,
>assuming that the router fills in the rest. In SIP, we did the same. We
>pass around URLs, which are interpretable independent of the context.

I think this is an argument, however unintentional, to eliminate
the tel: URI.  Without a tag to indicate context (which you are
arguing against), they are not "Uniform" Resource Indicators.

>I fully agree that users should not need to know about dial and number
>plans. I also agree that users should be able to dial extensions and
>local numbers as they do today in a PBX. I'd like to understand the
>costs involved in having internationalization of numbers done within the
>UA. Obtaining a dial plan automatically through a REGISTER response
>would still allow an administrator to control it, and to modify it
>(registrations get refreshed, so you can send updated versions in the
>responses of refreshes). So, my questions are: how complex can a dial
>plan be? How many entries in a dial plan table are there usually? How
>much processing power does it take to compare a number against a dial
>plan and internationalize it?

It's not as much a matter of processing power as the code to perform
internationalization and the size of the data necessary to do so.
As both Dean and Rick have pointed out, the dialing plans which
a phone may be required to understand can be very large and complicated
(especially within an enterprise or VPN environment). As Rick has
pointed out, he is currently running into very real memory limitations 
that make this processing impossible on the user agent.

You can argue about theoretical processing power and memeory necessary 
to perform these sorts of things, but I'm afraid that real-world
experience is going to have to trump theory. Imbedded clients
are *already* running into limitations that prevent them from doing
what you suggest they do.

-- 
Adam Roach, Ericsson Inc. |  Ph: +1 972 583 7594 | 1010 E. Arapaho, MS L-04
[email-masked]   | Fax: +1 972 669 0154 | Richardson, TX 75081 USA

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From: Henry Sinnreich <[email-masked]>
Date: Tue, 04 Jan 2000 14:46:49 -0600

Adam,

>(especially within an enterprise or VPN environment).

IP telephony gateways are now the priority model, but will not stay so
forever. At that point in time, a non-legacy oriented solution may be far
preferable, IMHO. A PDA or display phone screen may just be right for
[email-masked]...

BTW: The practically the only place in the WSJ where you can find phone
numbers are in ads. URLs dominate in all articles (quip credited to Chris
Cunningham).

Henry

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]]On Behalf Of Adam B.
Roach
Sent: Tuesday, January 04, 2000 1:50 PM
To: Jonathan Rosenberg
Cc: Adam B. Roach; [email-masked];
[email-masked]
Subject: Re: URL Generalization for Portability (was TRIP)

---

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 04 Jan 2000 17:05:45 -0500

> arguing against), they are not "Uniform" Resource Indicators.

No, its more an argument for using the tel URL when in its
internationalized form:

tel:+17327417244

The tel URL does allow for phone contexts that help identify where the
URL is valid. For
example, you can include a prefix as a context (like +1 516) to indicate
that the number
can only be called from that area:

tel:5551212;phone-context=+1516

This is useful when you imbed a tel URL in a web page in an intranet for
a company on 
Long Island. This way, the modem in the PC just dials 5551212; no area
code is needed
from there. Our application of the tel URL is slightly different. We are
not using them
to actual dial numbers from web pages. Rather, they point to resources
in the PSTN. In
that sense, I agree with Adam that what I think we want is for them to
be uniform, so
that they are resolvable from everywhere. This means they should either
be international
numbers, or be sip URLs which indicate where to go to get them resolved.

So, in the case of a gateway sending just dialed digits to a proxy, I
argued that we should use a SIP URL and put the contexts and stuff into
the user portion. Several folks complained about that; is it more
palatable to use the phone-context from the tel URL as part of the SIP
URL?

sip:[email-masked];phone-context=0000034

-Jonathan R.

-- 
Jonathan D. Rosenberg                       200 Executive Drive
Chief Scientist                             Suite 120 
dynamicsoft                                 West Orange, NJ 07052
[email-masked]                     FAX:   (732) 741-4778
http://www.cs.columbia.edu/~jdrosen         PHONE: (732) 741-7244
http://www.dynamicsoft.com