Design And Implementation Of SIP Functions In Embed IP-Phone

The session initiation protocol(SIP) is a part of IETF standard process ,which is setup on the simple message transfer protocol (SMTP) and Hypertext Transfer Protocol (HTTP) .Using the SIP can creating ,modifying and terminating sessions .It's simple ,scalable ,text-based features make it easy to implement session control ,scale control and mobility .For Telecom application SIP must unite with other protocol ,especially the connect of the real-time transfer protocol (RTP) and the Public Switched Telephone Network (PSTN) .There are many kinds of implementation based on SIP, such as embed-system, web 2.0,pc and so on.This paper discusses the applyment of SIP in VoIP,the stucture of SIP as well as its function and the exchanging signaling stream between two talkers in RFC3261.Using the Software Engineering method and thinking ,analyse a reduced SIP Stack which is based on a Embed System ,and add the REFER function to the stack .On this stack ,implement a IP phone application that based on SIP client . This SIP client is running on a reduce embed Linux system .It have main function of Linux .As the memory of system is limited ,this Client use C language to realize . This IP phone realize the Calling ,Calling Hold ,Calling Transfer function .At the same time realize the Multiple Calling .Today ,this IP phone is on stream ,and begin the ISP testing .This SIP phone can reduce the cost of comunation and provide high level quality.In this project ,the author is with responsibility for SIP client development ,design the process control function of SIP client ,and implement Calling ,Calling Hold ,Calling Transfer and the encrypt function .