Patent ID: 8472352

Claim:
A method for enabling a Call Waiting or Call Back service in an Internet Protocol Multimedia Subsystem (IMS) based communications network that comprises an originating part to which a calling party using a calling communication terminal is associated and a terminating part to which a called party using a called communication terminal is associated, the called party associated with the terminating part via a non-IMS based communication network, the method comprising: receiving at an application server in the terminating part a request-to-establish message from the originating part, the request-to-establish message having been formatted in accordance with the Session Initiation Protocol (SIP) and initiated by the calling party, supplementing the request-to-establish message at the application server with information formatted in accordance with SIP, the information indicating that the Call Waiting or Call Back service is desired by the called party, transmitting the supplemented request-to-establish message from the application server to an access node via which the called communication terminal is associated with the terminating part, at the access node, notifying the called communication terminal that the Call Waiting or Call Back service is applicable to a waiting call, and sending a confirmation formatted in accordance with SIP from the access node to the application server that indicates the called communication terminal has been notified of the waiting call.