[SIPForum-discussion] Query regarding SIP 183 Session Progress

[Banda, Srinivas (Srinivas)]

Hi Nikash,

183 with Require Header of 100rel means , it is mandatory that calling party should support the 100rel mechanism. If 183 has 100rel in Require it means Calle already supports it. So it is upto the implementation whether they can advertise again 100rel in Supported header too.

If the precondition is supported by the any party and don't want use in the session, they can just add in the Supported Header.
If they add in Require it means the precondition should be mandatory otherwise call will fail.

Usually all the supported information will be advertised in the INIVTE message itself.

Regards
Srinivas

From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Nikash N
Sent: Thursday, May 16, 2013 5:35 PM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] Query regarding SIP 183 Session Progress

Hi

I've a scenario here which I'd like to discuss.

Caller sends an INVITE with "100rel, timer, precondition" in supported header. The Callee responds with a 100 Trying and then a 183 Session Progress, in which the require header contains "100rel". Is there a necessity for the 183 to have "100rel" in supported header too? And if it supports precondition too, but does not want to use it for this session, does it need to specify that in the supported header?

Alternatively in a different scenario, if an INVITE does not contain a supported or a require header, can the callee respond back with a "supported" header containing "100rel". And then, if the caller supports 100rel too, and wants to use it, in what SIP message can he send a "require" header after these exchanges?

Thank you.

--
Regards
Nikash
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