Applying control theoretic approach to mitigate SIP overload

Abstract—The Session Initiation Protocol (SIP) retransmission mechanism is designed to maintain reliable transmission over lossy or faulty network conditions. However, the retransmission can amplify the traffic overload faced by the SIP servers. In this paper, by modeling the interaction between an overloaded downstream server and its upstream server as a feedback control system, we propose two Proportional-Integral (PI) control algorithms to mitigate the overload by regulating the retransmission rate in the upstream server. We provide the design guidelines for both overload control algorithms to ensure the system stability. Our OPNET simulation results demonstrate that: (1) without the control algorithm applied, the overload at a downstream server may propagate to its upstream servers and cause widespread network failure; (2) in case of short-term overload, both proposed feedback control solutions can mitigate the overload effectively without rejecting calls or reducing resource utilization, thus avoiding the disadvantages of existing overload control solutions for SIP networks.