Abstract: Provided are methods, devices and systems to augment a hosted SIP-PBX (Private Branch Exchange) installation with survivability features. The SIP survivability agent passively monitors ongoing SIP transactions between a local (enterprise) network and a remote (hosted) SIP service and learns the contact addresses of all parties. When the remote SIP service becomes unreachable, the survivability agent takes over the responsibility of the remote SIP service and connects the SIP sessions locally, allowing station-to-station, emergency, and external breakout calls.