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

["Peterson, Jon" <[e-mail]>]

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: [e-mail] [mailto:[e-mail]]
Sent: Thursday, September 05, 2002 11:18 AM
To: [e-mail]; [e-mail]; [e-mail]
Cc: [e-mail]; [e-mail]
Subject: Re: [Sipping] SUMMARY: Trunk groups in R-URI


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