According to sect. 7.1 of https://www.ietf.org/rfc/rfc3891.txt, when an INVITE is recieved with a replaces header, containing the call-id of another dialog, the receiving party needs to respond immediately with a 200OK containing the new INVITES call-id and cancelling the other call-id. In the below, Alice calls Bobs Desk but he's not there. He's in his lab, and hears the Desk ring, so does a dialoginfo call pickup.. Bob Bob Alice desk lab | | | *1 |-----INVITE----------->| | *2 |<----180---------------| Bob hears desk phone | | | ringing from lab but | | | isn't REGISTERed yet | | | | | |<--fetch dialog state --| | |---response ----------->| *3/4 |<-----INVITE with Replaces/200/ACK--------------| *5/6 |------CANCEL/200------>| | *7 |<-----487--------------| | |------ACK------------->| | | | | | | | I have a setup of OpenSIPS and FreeSWITCH. OpenSIPS loadbalances all INVITES to FreeSWITCH, and then any subsequent packets are just relayed on as a stateful proxy. With that in mind, see what happens if I try do the same.. https://pastebin.freeswitch.org/24660 - sip trace of.. 1. Alice calls bobs desk 2. Bobs desk rings 3. Bobs lab tries to pick up the call, so that bobs lab is the one speaking to alice and bobs desk stops ringing 4. Instead, Alice gets cut off and bobs desk ends up speaking to bob lab https://pastebin.freeswitch.org/24650 - FS logs of this issue As you can see, on line 19, Bobs lab sends an INVITE with a callid matching that of the one Alice established... FS sends a 200OK back.. All good so far. At this point I logically feel FS would then send a 200OK to the a dialog/Alice and bridge the two.. but instead it kills the dialog with alice and takes place directly with bobs desk.. tl;dr is FS handing replaces correctly here? Any advice would be much appreciated. Ben