Research And Implementation Of The Sip Protocol Stack

With the development of IP technology, which transferred in the IP Internet is more popular and more. To support the multimedia operation and supply the function such as call building and session control, the signal protocol is absolutely necessarily. The ITU-T has established the H.323 protocol to build the media conference system, and which is widely applied in the operation of IP telephone operation. But the H.323 protocol succeeds much idea of traditional telephone network, the protocol was complex and its realization is difficulty, so it can't completely adapt the require to transmit multimedia in the Internet environment. This thesis is study another protocol SIP proposed by IETF in this background.SIP is an application-layer control (signaling) protocol for creating, modifying, and terminating sessions with one or more participants. These sessions include Internet telephone calls, multimedia distribution, multimedia conferences, remote education and medical treatment.SIP invitations used to create sessions carry session descriptions that allow participants to agree on a set of compatible media types. SIP makes use of elements called Proxy servers to help route requests to the user's current location, authenticate and authorize users for services, implement provider call-routing policies, and provide features to users. SIP also provides a registration function that allows users to upload their current locations for use by Proxy servers. SIP runs on top of several different transport protocols and independent of these protocols.SIP use the C/S pattern, which is popular in Internet; its messages are expressed by text, simple and easy to realize; it has a good expansibility to support developing all kinds of increment operation. So the SIP is focused attention upon and itself becomes perfect gradually.This paper studies the function and specialty of SIP and compares the SIP and H.323.In the next, this paper deeply discusses the reliability, expansibility and security of SIP. At the same time, the design plan, framework and implement mode of SIP stack are studied and discussed. The SIP UA was implement and tested. At last it describes the realization process of Proxy Server, Redirect Server and Registar server.