[SIPForum-discussion] Query regarding SIP 183 Session Progress

[Nikash N]

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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