Study On A SIP-Based Presence Server And Its Application

Instant messaging (IM) and presence based Internet services have been one of the phenomenal growth stories.But these IM services are based on proprietary technology. With no technical standard to support interoperability between different service providers. The lack of standards prevented users on different online systems to exchange messages.SIP's(Session Initiation Protocol) open design makes it ideal for instant messaging and presence. For this reason, a SIP extension known as SIP for Instant Messaging and Presence Leveraging Extensions (SIMPLE) has emerged as the leading method of standardizing instant messaging and presence among various service providers. Like SIP, SIMPLE is an IETF(Internet Engineering Task Force) standard. Based on the principle of the SIP and the realization mechanism of expansion of SIP in the field of instant messaging and presence, one model of presence is proposed constructing a robust,secure,open enterprise system on foundation of this. This system can well realize the functions of presence. It not only indicates whether users are online,but also describe the constantly changeable communication way among users such us the willing, capacity, characteristic and ability etc. Thus a unified standard for instant messaging and presence is presented.In the process of implemented SPS system,I adopted SIP API(Application Program Interface) and SIMPLE PRESENCE API as an interface to SIP/SIMPLE entity on the top layer of this model.They are standard interface of Java.So all server and user agent based SIP/SIMPLE can interactive with SIP stack.SPS is designed with a open architecture.It is well configurable and extendable. It can implement function of presence as a standalone server.And work with the proxy,redirect server and registrar constructing a server.At the same time it is very easy to expand to adapt to the development of SIP.