Optimal routing for SIP-based session set up over IMS in mobile environment
International Journal of Internet Protocol Technology
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This paper proposes an extension of the functionality of a SIP proxy server for providing QoS to SIP-signalled voice over IP calls in a scalable and efficient way. The basic concept lies in aggregating SIP calls into bandwidth-provisioned trunks and on admitting calls on trunks only within the limit of their bandwidth. The SIP proxy server derives bandwidth requirements of SIP calls directly from parsed SIP messages. The bandwidth of the logical trunks can be dynamically changed. With a moderate trunk over-sizing, the trunk resizing rate can be kept much lower than the call arrival process. The approach scales well in a scenario where a centralized entity (bandwidth broker) is in charge of managing all the trunks of a given domain. We present simulation results that confirm this good scalability. The functionality and scalability of the proposed approach is compared with other ones currently discussed in the IETF or in the literature. Copyright © 2006 John Wiley & Sons, Ltd.