| With the development of network and communication, VoIP (Voice over Internet Protocol) becomes one of the key operations in NGN (Next Generation Network) technology. It brings more value-added business models for telecom and more interests for users. One of the most important things is instant communication service. Its core is Presence/IM technology. Users use voice communication, but also use the instant messages for written communication, and the Presence services for accessing to each other's situation, geographical location, communication media and other information. In the world, a number of different VoIP networks have been deployed, how to achieve the exchange is a serious problem.Currently, there are mainly two Presence/IM technical standards: SIMPLE and XMPP. The paper compares the two agreements'advantages and disadvantages, describes the subject's background (this topic is based on SIPSYS VoIP system, which completely follows SIP protocol), chooses the SIMPLE protocol, details research and analyzes SIMPLE standard files and related draft files, and designs Presence server and IM server in accordance with the standards. Users can communicate with each other by character words. The Server stores the unreachable messages. Users have buddy lists in the server, which supply friends'presence information. The Presence/IM system finally implements the functional requirements. The system conforms to SIMPLE agreement. It can intercommunicate with other standard Presence/IM systems.The First chapter introduces Presence/IM concept and background. The second chapter further introduces the present situation and the standards. The third,fourth chapter discusses the system demands,design and realization. The fifth chapter gives the figures of the Presence/IM system and the result of testing, and finally draws the conclusion. |
