Distributed approaches to S-CSCF selection in an IMS network

The IP Multimedia Subsystem (IMS) is a generic open-systems architecture offering converged multimedia services over IP. A function in the signaling plane of an IMS network is the interrogating Call/Session Control Function (I-CSCF) choosing the serving CSCF (S-CSCF) for a request. In this paper, we investigate distributed S-CSCF selection by considering four schemes: uniform random allocation, round robin, shortest expected delay, and least response time with network feedback. Through our study, we found that the shortest expected delay gives the best performance when the message size is one. However, when the message size of a request is higher, the shortest expected delay and the round robin scheme perform similarly in most cases while they are both better than uniform random allocation and least response time with network feedback schemes.