Patent ID: 7822407

Claim:
A method for a network to choose an authentication mode, comprising the steps of: a Serving-Call Session Control Function (S-CSCF) entity receiving a Message of register request from a subscriber and sending an authentication vector request carrying an authentication mode identifier to a Home Subscriber Server (HSS); and the HSS determining whether the S-CSCF requests authentication information of an Early-IMS-based authentication vector according to the authentication mode identifier; if yes, the HSS returning authentication information of the Early-IMS-based authentication vector to the S-CSCF; otherwise, the HSS determining type of the subscriber that requests access, if the subscriber supports a Full-IMS-based authentication mode, returning authentication information of the Full-IMS-based authentication mode, if the subscriber is 2G based, the HSS returning authentication information of the Early-IMS-based authentication vector to the S-CSCF or returning unsuccessful information to the S-CSCF; wherein the authentication vector request with the authentication mode identifier sent to HSS by S-CSCF further comprises information of access network type; wherein the subscriber that supports the Full-IMS-based authentication mode is 3G based; and wherein after the HSS determining that the S-CSCF requires authentication information of the Early-IMS-based authentication vector further comprises the HSS judging the access network type of the subscriber; if the access network is a 2G network, continuing with the process of returning authentication information of the Early-IMS-based authentication vector to the S-CSCF; if the access network is a 3G network and the subscriber requesting access is 3G based, returning authentication information that supports Full-IMS-based authentication mode to the S-CSCF; the S-CSCF receiving the authentication information, authenticating the subscriber that supports the Full-IMS-based authentication mode by adopting the Full-IMS-based authentication mode or returning access-rejected information to the subscriber.