Hello, Situation is : UAC -> Asterisk1 -> OpenSER -> Asterisk2 OpenSER is using tm module (t_relay and friends). When the UAC cancels an INVITE, the CANCEL is propagated to Asterisk2 which replies to the INVITE with a 487 and to the CANCEL with 200 OK. Both replies have the same ToTag, as rfc3261 9.2 suggests (SHOULD). The 487 reply is forwarded to Asterisk1 by OpenSER with the ToTag unaltered, but the 200 OK is forwarded as "200 cancelling" with a different ToTag (created by OpenSER). This messes up the transaction matching on Asterisk1 (which uses pedantic=yes in the sip.conf and has to stay that way) Is there a way to force OpenSER to use the ToTag of the incoming reply (the winning branch?) instead of it creating a new one? -- Greetings, Alex Hermann