Based On The Ims System, Instant Messaging Software

With the opening of China's telecom market and the issuance of 3G licenses, China's traditional telecom operators will become integrated operators who own the fixed and mobile networks. So how to achieve the next generation network (NGN) for network convergence has become a hot spot of the industry. At present, the technology of IMS (IP Multimedia Subsystem) which uses SIP (Session Initiation Protocol) and is irrelated with access get more widespread concern with the advantages in network convergence.Many businesses that IMS provides already exist on the Internet, but usually they are developed independently, and lack unified mechanism of trigger, control, management, use a lot of different techniques, different protocols. Therefore, the development of both terminal and application are more difficult. IMS provides a strong operational capacity and ability to integrate all their business using SIP, unifies the control of the business, which is convenient for our development of instant messaging software.This paper mainly discusses how to construct an instant messaging software with SIP in IMS. The main contents are:1. Research the architecture of the IMS, the entries and interfaces of the network, analyze the progress of registeration and session of IMS2. Research and analyze the protocol format of SIP, network elements of SIP, and protocol SDP used for session discription.3. Describe the designment and realization of the instant messaging software, the designment of the SIP stack, and the realization of the signals with the server side.4. Research and analyze the problem of NAT encountering in system development,and provide a solution to resolve it.