[OpenSIPS-Users] Bad ACK to negative reply

[Ben Newlin]

Hi,

I am seeing some strange behavior handling hop-by-hop ACKs to negative replies. A trace of my scenario can be found here: https://pastebin.com/Ve8rnYnu

The problem is that intermittently the OpenSIPS instance receiving the ACK is not recognizing. t_check_trans is returning false for this ACK.

The only thing I can see I that the Via header in the ACK is not the same as in the INVITE, which is required by the RFC. The ACK is missing the “i=03ba9232” parameter that was on the Via for the initial INVITE. This parameter was not on the initial INVITE and is being added by the OpenSIPS instance that is forwarding the INVITE. What is this parameter for? Shouldn’t it be included on the ACK? Can anyone see any other reason the ACK would not match?

Thanks,

Ben Newlin
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