Subject: RE: [Sipping] SUMMARY: Trunk groups in R-URI

From: "Peterson, Jon" <[email-masked]>
Date: Fri, 6 Sep 2002 14:06:45 -0400

SIP 'in general' means SIP for instant messaging and so on - SIP as a
non-telephony-specific protocol. There is no need for my instant messaging
client to understand or support the concept of trunk groups. But in
telephony contexts, obviously the concept of a trunk group is useful. 
 
I agree that my interpretation of the tel URL as a repository for
telephony-specific addressing may not be universally accepted - but I
haven't really canvassed for it in this forum, to date. I should probably
start. Though James Yu's draft certainly goes a long way towards that view,
were it to be ratified.
 
I think a good way to look at it would be like this: if I'm sending a
request to a gateway, it should have a tel URL in the Request-URI.
Otherwise, the gateway would have a hard time constructing a destination
telephony address (CPN in IAM, or whatever is relevant to the PSTN interface
of the gateway). I would say, in fact, that having a tel URL is a necessary
condition for sending a request through a gateway. If the scheme of the
Request-URI is 'tel:', then frequently it is also a sufficient condition for
sending the request to a gateway. Requests that are destined for a trunk
group, I think, must ultimately also be destined for a telephone number. In
other words, I think the times when a trunk group is likely to be specified
correspond to the times that a tel URL will be used, and the times that a
tel URL is not used, one should not have any need to specify a trunk group.
 
Jon Peterson
NeuStar, Inc.

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]
Sent: Thursday, September 05, 2002 11:18 AM
To: [email-masked]; [email-masked]; [email-masked]
Cc: [email-masked]; [email-masked]
Subject: Re: [Sipping] SUMMARY: Trunk groups in R-URI

In a message dated 9/4/02 7:21:45 PM Eastern Daylight Time,
[email-masked] writes: 

SIP in general has no use for a concept of 'trunk groups'; 
this is within the scope of telephony addressing, and belongs in the tel 
URL. 

[MAP] I'm further confused. If SIP has no use for the concept of 'trunk
groups', why is this discussion going on? 

I don't see that it is within the scope of "telephony addressing" either. I
understand the tel:url to be intended to carry the telephone number. The
current draft-antti-rfc2806bis-05.txt states that it is "for specifying the
address of a terminal in the phone network". Isn't that what "tel" means? I
suppose one could say that "tel" means "telephony" and that the header is
intended to carry all the extraneous parameters associated with "telephony",
but I din't think this was the accepted approach. 

From a functional point of view, if a need to carry a trunk group identifier
between entities really exists, it does not belong with the telephone
number. I think we need to determine where such a thing "functionally" fits,
not where it goes to keep the protocol pretty. 

Mike Pierce 
Artel

---

From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 06 Sep 2002 15:58:30 -0400

Peterson, Jon wrote:
> haven't really canvassed for it in this forum, to date. I should 
> probably start. Though James Yu's draft certainly goes a long way 
> towards that view, were it to be ratified.

I concur. Although perhaps a bit beyond the scope of the tel URL as 
originally defined (which was really for clicking on links in web pages 
that would place calls from a modem inside the computer), its certainly 
been evolving in that direction. I also believe that the direction is 
pretty consistent with general URI usage. We are talking about an 
identifier that poitns to a resource, and in this case, that resource is 
a line of some sort in the telephone network. That may or may not be an 
actual telephone, and I think thats fine. After all, a SIP URL can 
represent a phone, a user, a device, a service, a conference, or 
whatever, and I think this generality is a strength.

-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

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