Abstract: SIP(Session Initiation Protocol) plays an important role in 3G environment, and JAIN SIP implemented SIP by Java language. After the introduction of SIP standard, we analyzed the architecture and implementation mechanism of JAIN SIP, then described its development process using code segments and interactive graphs. Developing SIP-based applications with JAIN SIP will improve the development efficiency and the applications will gain high reliability and portability.

Key words: JAIN(Java Advanced Intelligent Network, register process