ISE03-3: Towards Stateless Core: Improving SIP Proxy Scalability

The Third Generation Partnership Project (3GPP) specified the IP Multimedia Subsystem (IMS) standard. This standard uses the Session Initiation Protocol (SIP) to setup and teardown multimedia sessions through a potentially large chain of proxies. The IMS standard allows some core elements to be deployed as transaction stateful or stateless proxies. Moreover, SIP standard allows proxies decide when to store transaction information on a per request basis. In this paper, we examine the implementation of these core IMS proxies. We propose an algorithm that determines for each incoming request when to store transaction information. The goal of this algorithm is to increase throughput by reducing the number of transactions without compromising call setup times. Our algorithm uses information such as the incoming SIP request, CPU usage, and the number of retransmitted messages. We have implemented this algorithm in our IMS simulation tool. The results show that the system throughput can be improved by as much as 46%.