Subject: [Sipping] How to support CFT (conformation Tone) in SIP network?

From: NC Reddy <[email-masked]>
Date: Mon, 6 Dec 2004 14:36:33 +0900

Hi, 
   Pls find the problem as follows and suggest your recommendation
solution for it.

Back ground:
We have to provide for new service to calling party (i.e caller) named
as CFT (Confirmation Tone) for to know either off-net call or on-net
call by distinctive ringing at calling party. So calling party knows
that whether he/she want to continue the call or not.

Off-net call: it means the call outside the service provider domain.
On-net call: it means the call is inside service provider domain.

So by giving CFT tone to calling party he knows that what's the type
of call he started, so depends the type of the call he may  continue
or not. If the call is on-net it's free call and if it's off-net it
charged according to service provider billing.

Problem:
We have to send CFT information to calling party before the call
initiating towards the called party i.e before ringing at called party
side.
So we are thinking use INFO method pre-dialog establishment i.e before
18X msges. And INFO has the information about the called party type
i.e off-net/on-net.

But according SIP standards INFO method for mid-call session
information i.e after 18x. So instead of modifying the standard SIP
behavior, can we pass that information in 183 session in progress
msg??

pls throw some light on this kind of problems.

Thanks and Regards
Channa

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---

From: Adam Roach <[email-masked]>
Date: Mon, 06 Dec 2004 02:21:20 -0600

You probably want to take this to the sip implementors list; this is 
exactly the kind of question that it's meant for.

That said, I'll point out that you're approaching this the wrong way. 
You're trying to figure out how to apply a very PSTN-like solution to 
the problem to a SIP network. This usually leads to frustration.

Instead, you need to go back to what your requirements are, and figure 
out how they can be met using SIP mechanisms.

 From what you've written, I infer that your fundamental requirement is 
something like: "Users must be able to determine, prior to a call being 
established, whether they are willing to complete off-net calls."

Then, a SIP-like way to solve this kind of problem would be for the user 
to indicate -- before the INVITE is sent -- whether they are willing to 
initiate calls that terminate off-net. This indication would be present 
in the INVITE itself.

But, in any case, you'll need to extend the protocol to support what you 
propose. There isn't a way, using currently defined mechanisms, to do 
what you want. I would suggest that, if you decide to extend the 
protocol, you do it here instead of coming up with some proprietary 
solution that is unlikely to work in the wild.

/a