Modeling of Priority-based Request Scheduling Mechanism for Finite Buffer SIP Servers

In this paper, we present a fluid-flow model to characterize the behavior of the overloaded Session Initiation Protocol (SIP) server with a finite buffer. Our model includes a priority-based request scheduling mechanism (PRSM) which diminishes redundant retransmissions to overcome the overloading of SIP servers. The numerical results closely match with the simulation results, indicating that the proposed models can accurately capture the dynamic behavior of a SIP server with the PRSM. Using the Markov Modulated Poisson Process (MMPP) traffic model, the failure ratio of the PRSM is reduced to zero when the buffer size is higher than 1K while it linearly increases for the conventional SIP. The mean response delay of the PRSM is kept constant around 175 ms while it reaches as high as 179 seconds for the conventional SIP when the buffer size is around 200K.