The title says the opposite of the mail's contents, btw:
RFC3960, gateway model gives guidelines about the, let's say, "correct"
behavior. The main rule says more or less "media has always the precedence".
About the scenario you mentioned in the text, i.e. 183/SDP and then 180 (no
SDP I assume) you should play a local ringback ONLY in the case you don't
receive any media (despite the media channel has been established).
In the reverse case, i.e. 180/noSDP and the 183/SDP the rule is the same,
meaning you should play the media. Should the media missing, you would
continue to play the local ringback due to the 180.
This is what RFC3960 says. In the real world (especially when you
interoperate to the PSTN) it doesn't work in some case. My recommendation is
to always use the latest received message as the most significant. Then, in
the first case once receiving the 180 I would suggest to play a local
ringback stopping playing the media, in the second one to stop the local
ringback and play the media (if any). Using this approach, I didn't find yet
any failing case when interoperating with PSTN (this is the most complex
scenario usually) in the operator's network I'm working with.
Andrea
Message: 2
Date: Wed, 27 Feb 2008 14:53:44 +0800
From: "A C Sathish-a22713" <[EMAIL PROTECTED]>
Subject: [Sip-implementors] Query on UAC Behaviour for 180 Ringing
followed by 183 with SDP.
To: <[email protected]>
Message-ID:
<[EMAIL PROTECTED]>
Content-Type: text/plain; charset="us-ascii"
All,
Can someone give some pointer on what should be UAC behaviour, when
it receives 180 Ringing after receiving 183 Response with SDP .
Should UAC play local ringing ? Can some one give some draft reference
for UAC behaviour of this scenario.
Regards,
-Sathish
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