RTP Proxy is a VoIP Media Relay which runs in Linux and is open source. http://www.rtpproxy.com/ There is a control channel (TCP) which is established to inform the SIP Switch about a media timeout, at present this is specified as a argument when the application is started. Additionally when a new session is established the control channel information is passed into the new session. If the session control channel matches the argument passed in at startup, then timeout notification will be enabled raising a TCP event at a predefined interval after no media is detected. Required Change ?We wish to modify the checking behavior and/or allow a list of possible authorized SIP Servers to be passed in. The code change is VERY minimal, possibly even just 1 line, however we must ensure that this is undertaken by an experienced developer as we cant afford a single bug to be introduced.