Priority Queuing Strategy for Self-Overload Control in SIP Servers

The Session Initiation Protocol is an IP based application level signaling protocol. SIP is used for locating end users, establishing, modifying and closing multimedia sessions between end users. SIP uses various overload control techniques out of which self-overload control using queuing strategies is one. This research work identifies the problem arising due to retransmission of SIP requests and introduces an Advanced Smart Priority Queuing Model to increase the reliability of SIP server, by reducing the retransmissions. SIP request retransmissions can be reduced by giving high priority for requests starving in queues for longer durations. The reduction in SIP retransmissions avoids unnecessary load on downstream network. We evaluated the reduction in queuing delays and the stability condition, for identifying the capacity of the SIP server, and validated the same using simulation method. We compared the server recovery time when using FIFO Queuing Strategy and Smart Priority Queuing Strategy with proposed Advanced Smart Priority Queuing Strategy. With Advanced Smart Priority Queuing Strategy, the capacity of the SIP servers has been increased by 81.90% and server recovery time has been reduced by 83.63%.