Queuing Model for Loss-Based Overload Control in a SIP Server Using a Hysteretic Technique

摘要

In this paper, we develop a mathematical model of a load control mechanism for SIP server signaling networks based on a hysteretic technique developed for SS7 from ITU-T Recommendation Q.704. We investigate loss-based overload control, as proposed in recent IETF documents. The queuing model takes into account three types of system state - normal load, overload, and discard. The hysteretic control is made possible by introducing two thresholds in the buffer of total size B - the overload onset threshold H and the overload abatement threshold L. We denote the mathematical model using the modified Kendall notation as an M|G|1| (L, H) B queue with hysteretic load control. We also develop an analytical model for the case of an M|M|1 queue and a simulation model for an M|.D|1 queue. We investigate the return time from an overload state as the target performance measure of overload control in a SIP server, and provide numerical examples in order to examine the difference between the MM1 and M|D|1 systems.