Re: [reSIProcate] PRACK with late offer?

[Scott Godin <sgodin@xxxxxxxxxxxxxxx>]

This scenario should work.  If I'm understanding your scenario correctly you are the UAC side and the UAS has provided it's offer in the 183 message.  You would need to call provideAnswer before the PRACK is sent out by DUM.

Best Regards,

Scott Godin

On Mon, Mar 7, 2016 at 6:12 AM, Jan Granqvist via resiprocate-devel <resiprocate-devel@xxxxxxxxxxxxxxx> wrote:

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---------- Forwarded message ----------
From: Jan Granqvist <jan_granqvist@xxxxxxxxx>
To: "resiprocate-devel@xxxxxxxxxxxxxxx" <resiprocate-devel@xxxxxxxxxxxxxxx>
Cc: 
Date: Mon, 7 Mar 2016 11:11:14 +0000 (UTC)
Subject: PRACK with late offer?

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