Performance analysis of multi-party conferencing in IMS using vacation queues

The IP multimedia subsystem provides a platform for group communication services using Session Initiation Protocol (SIP). SIP supports the services where participation of multiple users is involved. The centralized conferencing framework limits the ability to have large number of participants because of the overhead on the server. In this paper, an efficient solution for enhancing the capability of the system to handle multiple requests at a time is provided by presenting a queueing model for SIP message aggregation at the edge-proxies. This queueing system is analysed as a vacation queue with batch arrival and batch service to describe the arrival and processing of bulk SIP messages. The steady-state results for QoS-aware SIP signaling system are obtained from the queueing model. Further these results are verified using NS-2 simulation. In addition, the optimal value of the timer and threshold values that dynamically controls the SIP message queue associated with QoS constraints are obtained using numerical optimization technique.