I have just implemented a new elastix 1.3-2 and am finding out some of my outbound calls after 4 to 10 sec of the call it will get dropped however some calls are established with out any problems. I have connected my sip provider (Bandtel) and they are saying the UAC is not sending a call acknowledgment after the call is made. this is what they are telling me --- I will refer to the outbound calls you place where you are acting as the UAC. or client. section 18.104.22.168 clearly states in paragraph 3 " The UAC core MUST generate and ack request for each 2XX received from the transacton layer" since you are using asterisk it is most likely only a couple causes of the issue. 1 is that the core is not functioning correctly or 2) the security levels are set up so that if the DNS resolution takes place after a call is in the invite state and the signaling IP changes the original address is not used but the new address is used. or the message is blocked all together --- question is has anyone had this issue or have any thoughts on a fix ? Thank you .