Efficient Link Utilization of SIP Proxy Server for Reducing Load in FoIP Application

Abstract

It’s been some time now that expressions like “Voice over IP”, “Fax over IP” and the likes are heard extensively in the telecommunications industry. The idea is utilizing data networks to deliver telecommunications services which are currently provided by the PSTN. The incentive is pretty straightforward: cutting costs and yet being able to provide the previous services, not to mention the added capabilities to deliver a multitude of other services, hardly imagined feasible with the PSTN.

When considering the implementation of the aforementioned objective, one faces a lot of difficulties. Simply put, the current data networks, e.g. the Internet, have not been designed with telecommunications services in mind. They have been optimized to carry data which is bursty in nature. This design is in obvious contradiction to the requirements of the telecommunications services, one of which is fax. In this dissertation, Fax over Internet protocol (FoIP) is being considered which has two possible approaches to be accomplished: Real-time and Store-and-Forward. Real-time approach is the ultimate goal since it is the realtime faxing which makes the transition from the PSTN to the Internet-based architecture smooth.

Signaling comprises initiation, management and tear-down of sessions examples of which are fax, voice, video and the like. Currently there are two protocols that can provide an end-to-end solution: H.323 and Session Initiation Protocol (SIP). SIP is the protocol of choice among other standards in the voice and fax transmission domains due to its numerous advantages. In this dissertation, It is intend to closely examine some aspects of the new architecture and its implementation feasibility. Different components of the realtime Fax over IP architecture are analyzed and attention has been paid to the signaling part. Utilization of SIP in conjunction with SDP, as companion protocol to SIP for capabilities to exchange for fax transmission has been studied. What It is intend to do is exploring whether fax parameters details can be negotiated using SIP/SDP. Session establishment, starting a sample file transfer, which can act on behalf of real-time fax transfer, and the subsequent session tear-down, after file transfer is complete, are demonstrated. This simulation scenario and its results exhibit the potential success of the proposed SIP/SDP combination for real-time fax session establishment, management and tear-down.

Another important analysis carried out in this dissertation is the utilization of SIP contact header for reducing the load on proxy servers which is a highly desirable feature.