Patent ID: 8295158

Claim:
A session processing method in an Internet Protocol multimedia subsystem, wherein the method comprises: receiving an initial request for a called user by an Interrogating-Call Session Control Function (I-CSCF); inquiring, by the I-CSCF, a Home Subscriber Server (HSS) about a registration location of the called user; receiving, by the I-CSCF, a response from the HSS; sending, by the I-CSCF, a Session Initiation Protocol (SIP) request to a Serving-Call Session Control Function (S-CSCF) according to the response from the HSS; determining, by the I-CSCF, whether a response from the S-CSCF has been received within a prescribed period of time; and reselecting an S-CSCF if receiving no response from the S-CSCF within the prescribed period of time, and sending a SIP request to the reselected S-CSCF, by the I-CSCF, wherein the process of reselecting an S-CSCF comprises: obtaining a set of S-CSCF capabilities required by the called user from the HSS by sending to the HSS a location information request, wherein the location information request comprises at least one of a command Cx-Location-Query, which is extended by newly adding an information element in the command Cx-Location-Query, and a command Cx-Select-Pull, where an IMS Private Identity (IMPI) attribute type of the command Cx-Select-Pull is modified as being conditional, reselecting an S-CSCF in accordance with the set of S-CSCF capabilities.