Patent ID: 8549153

Claim:
A session control method in an IMS, comprising: forwarding, by a third Interrogation-Call Session Control Function, I-CSCF, a session request of a first User Equipment (UE) to an available third Service-Call Session Control Function, S-CSCF, according to address information of the third S-CSCF if a second S-CSCF bound with a second User Equipment (UE) involved in a current session fails, upon reception of the session request of the first UE transmitted from a first S-CSCF bound with the first UE; and instructing, by the third S-CSCF, the second UE to renew initialized registration through a second Proxy-Call Session Control Function, P-CSCF, bound with the second UE according to address information of the second P-CSCF or obtaining service registration information iFC of the second UE from an HSS and switching the current session to the second UE according to the address information of the second P-CSCF bound with the second UE and the iFC, wherein forwarding, by a third I-CSCF, a session request of a first UE to an available third S-CSCF, according to address information of the third S-CSCF if a second S-CSCF bound with a second UE involved in a current session fails comprises: requesting, by the third I-CSCF, an Enhanced-Domain Name Server, E-DNS, for address information of the second S-CSCF; transmitting, by the E-DNS, address information of the available third S-CSCF to the third I-CSCF upon determining, from results of monitoring S-CSCFs, that the second S-CSCF fails; and forwarding, by the third I-CSCF, the session request of the first UE to the third S-CSCF according to the address information of the third S-CSCF returned from the E-DNS, and wherein before the third I-CSCF receives the session request of the first UE transmitted from the first S-CSCF bound with the first UE, the method further comprises: requesting, by the first S-CSCF, the E-DNS for address information of a second I-CSCF to which the second UE belongs upon reception of the session request of the first UE; transmitting, by the E-DNS, address information of the available third I-CSCF to the first S-CSCF upon determining, from results of monitoring I-CSCFs, that the second I-CSCF fails; and forwarding, by the first S-CSCF, the session request of the first UE to the third I-CSCF according to the address information of the third I-CSCF.