[SR-Users] Question about early media

[Andreas Heise]

Hello,

you could change the SDP with UPDATE method, but 183 must be send reliable
in this case.

regards,
Andreas


2010/10/5 Iñaki Baz Castillo <ibc at aliax.net>

> 2010/10/4 Asim Riaz <ariaz78 at gmail.com>:
> > Hi List,
> > Phone-1 ------->Proxy1 (kamailio)-------------->Proxy-2(3rd party)
> > -------------> phone 2
> >
> > Calls from phone-1 to phone-2, proxy-2 is sending early media without sdp
> in
> > provisional reply, this early media is sourced from different port than
> > response (200), what port proxy-1 will use to transmit actual voice, the
> > source port in early media or source port in  response(200) which is
> > different than early media.
>
> As Daniel said Kamailio doesn't handle media (it's a SIP proxy). You
> should mean "Phone-1" instead of "proxy-1".
>
> According to the RFC about SDP (and also RFC 3261): during the same
> early dialog (same To-tag) the SDP MUST NOT change. This is, if a UAS
> generates a 183 (To-tag=1234) with SDP, it MUST use the same SDP in
> other 183's responses and in final 200 OK response.
> The client can receives multiple SDP (when there is a proxy doing
> parallel forking, but each early dialog (same To-tag) MUST mantain a
> fixed SDP.
>
> So, if the client receives a different SDP in the 200 than the SDP it
> received in the 183 (I mean in the *same* early-dialog / same To-tag)
> then the client MUST ignore others SDP but the first one received. I
> insist: I'm speaking about the SDP in the SAME early-dialog.
>
>
>
> --
> Iñaki Baz Castillo
> <ibc at aliax.net>
>
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