Subject: Re: [Sipping] Do Phones Have Dial Plans, or do Proxies map? was RE: [Sippin...

From: [email-masked]
Date: Thu, 9 Jan 2003 14:59:57 EST

In a message dated 1/9/2003 2:08:43 PM Eastern Standard Time, 
[email-masked] writes:

> First we should decide if we put the dialing plan in the phone.
> 
[MAP] As I see it, there are only two possibilities to handle a SIP call (not 
just emergency calls):

1. The phone knows the dial plan for the area it is in
2. The outging proxy knows the dial plan (of the originating phone)

WIth option 1, it is clearly unworkable for the dial plan (including 
knowledge of what the emergency number is) to be built into a phone.

It would seem to be out of the question to expect an arbitrary proxy to know 
the dial plans for all areas of the world, so I must presume that the only 
workable scheme for option 2 is for the outgoing proxy to be "local" to the 
orginator.

(There is, in effect, another case, such as the satellite service some have 
mentioned, in which the orginator has no "local" dial plan, that is, there is 
no expectation of being able to reach "local" things like emergency, repair, 
the local TV station by dialing #13, the highway patrol by dialing #77, etc. 
The only thing that can be dialed is an E.164 number, or specific "service" 
numbers that the satallite service provider themselves defines and uses.)

So there are two possibilities (when there really is a "local" dial plan):

1. A phone is loaded with the dial plan when it "registers" for service, with 
the information coming from some "local" server. It can then know when 
dialing is complete without a "Send" key, and can send the appropriate 
tel:uri (E.164 number, SOS, etc.).
2. The phone knows nothing about the dial plan, depends on the user hitting a 
"Send" key (like cellualar) and the "local" outbound proxy does all 
interpretation of the dial digit string. The phone knows nothing about 
emergency calls.

Certainly both of these should be allowed.

(If you want an example of what could be required to send a dial plan to a 
phone, one can reference RFC 2705.)

Mike Pierce
Artel