Re: [Sip] Re: Offer by the callee

[Juan-Carlos.Rojas@alcatel.fr]

Hi Gonzalo,

An example.
Alice calls her bank, using an audio stream only; Alice is a good customer.
Bob, the Alice's account manager, receives the call, and his terminal is
pre-programmed to offer automatically a video stream also and high-quality
voice codecs, for good customers.
Therefore:
- Offer-1 from Alice to Bob: one audio stream with normal voice codec
- Offer-2 from Bob to Alice: one audio stream with high-quality codec (not
necessarily present in Offer-1, but including supported codecs from Offer-1
to give a fallback possibility), and one video stream

As Offer-2 is pre-programmed in Bob's terminal, it is useless for A to
start resource reservation for Offer-1.
So in the scenario, I was using:
- 183 response, to allow Bob to tell Alice "I'm handling your session
invitation", so it is not a final response carrying an error message
- all port numbers equal to zero, to tell Alice "wait a minute, don't start
resource reservation"
- and the UPDATE message from Bob to Alice will follow immediatly after 200
Prack with the new offer Offer-2 (this is suggested by the scenarios in the
Update draft)

Obviously, there is a charging model behind that, but this is another
story. Anyhow, Alice has always the possibility to reject the Offer.

Best regards
Juan Carlos





Gonzalo Camarillo <Gonzalo.Camarillo@lmf.ericsson.se> on 21/03/2002
05:30:42

To:   Juan-Carlos ROJAS/FR/ALCATEL@ALCATEL
cc:   Jonathan Rosenberg <jdrosen@dynamicsoft.com>, sip@ietf.org
Subject:  Re: [Sip] Re: Offer by the callee


Hi,

what do you want to put in the offer-2 to be sent that you cannot put in
the answer-1? Understanding the scenario you have in mind would be
helpful...

Gonzalo

Juan-Carlos.Rojas@alcatel.fr wrote:
>
> Hi Gonzalo,
>
> Thank you for your answer
> You are right, but sending a held SDP does not prevent the calling party
to
> start resource reservation, but only to send media.
> I agree with you that normally, a port number to zero indicates refusal
of
> the media stream. Nevertheless, according to Offer/Answer draft, all port
> numbers equal to zero is used also to announce capabilities (section 9),
> and very often it is used to say just "don't use this media".
>
> What I need here is to give to the answerer the possibility to say
"Mr.the
> Offerer, I'm not rejecting your Invite, but I'd like to send you a new
> offer right now, so it is useless to start resource reservation before
> receiving this new offer"
>
> Best regards
> Juan Carlos





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