Vikram Chhibber wrote:
> Hi,
>
> I want to perform page-mode instant messaging (using SIP MESSAGE) on a
> dialog created by INVITE. This INVITE I want for establishing a dialog
> on which I can send SIP MESSAGE only and there will be no media. I do
> not want msrp either.
The first question is *why* you want to do this, and whether you should.
If you establish a *session* for sending page-mode messages, then you
are really doing session-mode messaging. Long ago the need for session
mode messaging was identified, and this approach was considered. It was
then abandoned in favor of the MSRP approach.
So, if you are trying to create a mechanism for doing session mode IM
you are encouraged to *not* do this, and instead use MSRP.
IIUC, Microsoft does use MESSAGE within an INVITE dialog usage. I think
they did it before MSRP was adopted. I suppose if your goal is to
interoperate with them then you ought to do whatever they expect.
> In this case, how should I construct offer and then answer SDP?
> SDP with no m line should be fine but is there some media description
> defined for this purpose?
Mechanically you can create an SDP offer that has the required lines but
doesn't have any m-lines. It constitutes a legal offer, and if you can
get somebody to accept it then you are on your way.
The problem of course is that an offer with no media is odd - there is
no real hint what the point of it is, so a UAS is likely to reject it.
What you want is some way to indicate the purpose of the session and how
you intend to communicate.
AFAIK there is no *standard* way to do it. I think MS uses some special
m-line for the purpose. But I have no details.
Paul
> Thanks,
> ~Vikram
> _______________________________________________
> Sip-implementors mailing list
> Sip-implementors@lists.cs.columbia.edu
> https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
>
_______________________________________________
Sip-implementors mailing list
Sip-implementors@lists.cs.columbia.edu
https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
