[SR-Users] Question about early media

[Asim Riaz]

Thanks for the input, proxy-2 which is 3rd party sending early media without
SDP info in pregress message(180 or 183).



On Tue, Oct 5, 2010 at 7:47 PM, Andreas Heise
<aheise.lists at googlemail.com>wrote:

> 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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>>
>
>
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