PRACK with late offer?

[Jan Granqvist]

Hi all,
I need some pointers on how to use 'PRACK'.We have been using the late offer model in some required cases with no problem.Now we will be connecting towards a SIP trunk that requires 'PRACK'. I've enabled 'PRACK' support and it works when providing an offer in the initial 'INVITE'.But I'm a bit at loss when trying to combine 'PRACK' support with late offer, what the call flow should look like.
UAC                              UAS(Sip trunk) |------------------INVITE---------------->| |<---------------100 Trying--------------| |<--183 Session Progress w/SDP--| |<--183 Session Progress w/SDP--| |<--183 Session Progress w/SDP--| |-----------------CANCEL-------------->| |<-----------------200 OK----------------|
The initial 'INVITE' includes 'PRACK' support in the 'Allow' header and also '100rel' in 'Supported' header.The '183 session progress' includes header '100rel' in 'Require' header as well as a 'RSeq' header, but DUM doesn't respond with a 'PRACK'.While looking through the UASPRACKFlows.png (resip/dum/doc), scenario 1 looks like what I'm looking for.
What should the proper way be in this case? Is it possible to have this combination, 'PRACK' with late offer?I'm using version 1.10.0.
BR/Janne
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