We need to develop a SIP to Viber gateway. The gateway should be able to pass voice calls incoming over SIP and forward them through Viber to complete the call to the called party number. The development platform/operating system is not important. The project should be completed either by using the Linux/Windows Viber executables, or by using the Android /Symbian/ Windows Phone mobile versions of the application, no matters on the version number. The implementation should return the correct call error codes to the SIP backend, i.e. CALL SUCCESS, BUSY, UNAVAILABLE, etc. For a successful project we'll select the one, triggering successfully continuous SIP/Viber calls.