A cooperative overload control method for SIP servers

Voice over IP applications are becoming popular due to proliferation of smart phones. Many people are using Internet on these devices. To support millions of VOIP users and increase QoS (Quality of Service) VOIP installations employs large number of SIP Proxy servers to route calls. To achieve high throughput and minimum response times usually a load balancer is used to dispatch calls to SIP proxy servers. Overload control in SIP is a well known problem in SIP proxy servers. Local overload control, hop-by-hop and end-to-end overload control methods are used in SIP networks. Stand-alone overload control method monitors the processor and memory resources of the proxy server where overload control is implemented. It does not avoid the overload in entire SIP network. In this paper we developed a novel cooperative overload control method to detect and control overload in SIP servers. We have implemented the algorithm by modifying leading open source kamailio SIP proxy server. We have evaluated our algorithm by experimental test setup and found results are outperforming the standard standalone overload control algorithms in terms of throughput and response time.