This is pertaining to call cancel operation where the calling UA sends a CANCEL request via openser to the called UA.

After the UA sends ACK in response to 487 Transaction Terminated response, 487 responses are re-transmitted by openser to the UA as if the SIP proxy didn't regcognise the ACK request. I have tested with other UA and compare the differences between the ACK sent by UA that worked and UA which has this problem. The difference is that the ACK sent by the UA having this problem has a route header added.

Foon-Yew Kok

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