IP Multimedia Subsystem (IMS) is a generic open-system architecture offering converged multimedia services over IP for the wireless world. The Session Initiation Protocol (SIP) is used for the signaling plane in the IMS networks. Various SIP proxies are defined by 3GPP for the IMS signaling, commonly known as CSCF (Call/Session Control Function). I-CSCF acts as a load balancer during the IMS registration phase and selects the "best-fit" S-CSCF for the user. It is crucial to select the best S-CSCF because it is directly related to the QoS; this study focuses on the algorithm to be used and the protocol to feed the necessary data to the algorithm. First, we will describe the service-delay driven algorithm, compare it against the current 3GPP and Motorola algorithms and show the practical advantages of using our algorithm. Second, we will describe the update delay protocol on top of SIP for exchanging delay related information.
Plarent Tirana is a Solutions Architect for Openwave Systems Inc. Currently he designs and implements solutions for large US carriers in messaging and location based services areas. Previously he worked for Sun Microsystems Inc (professional services) where he implemented custom solutions mainly in the telecommunications market. He is currently working towards his Ph.D. degree from University of Missouri in Kansas City, Department of Computer Science and Electrical Engineering. He holds a BS and MS degree in Telecommunications and BS in Electronics. His current interests include: networks signaling and routing, Fixed to Mobile Convergence, Location Based Services and IP Multimedia Subsystem.