Patent ID: 8494521

Claim:
In a node of an Internet Protocol Multimedia Subsystem (IMS) network, the node configured with a Serving Call Session Control Function (S-CSCF) and supporting restoration procedures, a method for obtaining at least a portion of the user's registration backup data from a Home Subscriber Server (HSS) of the IMS network, without overwriting at least a portion user's multi-registration backup data commonly used by multiple access technologies stored in the HSS, when a subsequent registration occurs for the user and when the node lacks registration data, the method comprising: receiving, from a User Equipment (UE), a Session Initiation Protocol (SIP) registration request message that carries at least an IMS Private User Identity (IMPI) and IMS Public User Identity (IMPU) pair; in response to receiving the SIP registration request message, determining: a) a lack of registration data corresponding to the IMPI and IMPU pair stored by the node; and b) that the SIP registration request message includes a reg-id parameter, which indicates that the SIP registration request message relates to a multi-registration associated with the IMPI and IMPU pair; sending a Server Assignment Request (SAR) message to the HSS, wherein the SAR message carries the IMPI and IMPU pair, a parameter for identifying that the SAR message relates to an initial registration of the user, and a multiple registration indication, which indicates that the SAR message relates to a multi-registration associated with the IMPI and IMPU pair; and receiving a Server Assignment Answer (SAA) message carrying registration backup data corresponding to the IMPI and IMPU pair from the HSS.