Hi Jarod,
Thanks for the quick feedback. really appreciated...
In the current setup, the endpoint A (sofia) is not advertising 100rel in
the INVITE which implies that the Proxy should not expect any PRACK. This
means that the bullet 2 of your answer is more appropriate.
In the event that the Endpoint A is advertising 100rel and the proxy
expecting PRACK, I am interested to understand why it would have any
impact on the SDP of the 183/200. Can you share with me how PRACK can
allow the SDP to change between 183 and 200 with respect of rules
described in RFC 3261, Section 13.2.1.
Thanks in advance,
Louis Guindon
Jarod Neuner <j.neu...@networkharbor.com>
2011/10/12 12:34 PM
To
Louis Guindon <louisguin...@vtech.ca>,
"sofia-sip-devel@lists.sourceforge.net"
<sofia-sip-devel@lists.sourceforge.net>
cc
Subject
RE: [Sofia-sip-devel] 183 early media description different from 200Ok
media desription
Three points of interest here.
1) By default, NUA supports the 100rel extension described in RFC3262.
Since the proxy is sending a 183 response, it seems likely that it is
requesting a PRACK. Have those messages been omitted in the provided call
flow?
2) If the proxy was not requesting a PRACK, Sofia-SIP is required to
ignore the SDP in the 200 OK, in accordance with rules in RFC 3261,
Section 13.2.1.
3) If arguing with the vendor isn't an option, you should be able to pull
the unparsed SDP from the sip_t structure. From there, a session
re-negotiation might sync up the stack.
Hope this helps.
-Jarod
From: Louis Guindon [mailto:louisguin...@vtech.ca]
Sent: Wednesday, October 12, 2011 1:37 PM
To: sofia-sip-devel@lists.sourceforge.net
Subject: [Sofia-sip-devel] 183 early media description different from
200Ok media desription
Dear All,
I am experiencing a problem with the Sofia SIP stack with early media.
Here the flow:
A (Sofia) Proxy B
|-----------INVITE----------->| |
| |----- INVITE ---------->|
| | |
| |<------ 100 ------------|
|<-----------100--------------| |
| | |
|<-----------183--------------| |
| (Media Source Proxy) | |
|<===========RTP=============>| |
| |<------ 200 ------------|
|<-----------200--------------| |
| (Media Source B) | |
|<===========================RTP=======================|
| | |
|------------ACK------------->| |
| |------- ACK ----------->|
| | |
During the call setup, the Proxy sends early media so tones (ringback) is
generated by the proxy. When the endpoint B answers the call, the SDP in
the 200OK contains media description for the endpoint B. The RTP
Problem: The stack seems to assume that the SDP payload received from a
183 would be the same as the one received with the 200OK. Thereof, the
stack ignore reporting the SDP from the 200OK and doesn't intialize the
SDP structure pointer when the stack has previsously received SDP as part
of the 183. The application cannot retrieve the SDP information to update
the RTP stream direction which cause one-way audio.
Question: How can we force the stack to populate the NUA SDP structure
members in that case? Any idea would be welcomed...
Regards,
Louis Guindon
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