Design And Implementation Of Enterprise Communications Server System Based On SIP

Nowadays, the Wireless Local Area Network (WLAN) has been widely used in the world, at the same time, the price of intelligent terminal has been cheaper and cheaper. Under such circumstances, the VoIP-based telephony applications can bring lower cost of the communications. The VoIP (Voice over Internet Protocol) was defined based on the WLAN, didn’t need the participation of telecom operators, reduced the costs of communication, and it also flexibly combined the voice and data in a perfect way, so it improved the convenience of communication. The core protocol of VoIP is SIP (Session Initiation Protocol).This thesis implemented the key signaling protocol (SIP) in VoIP. Programmed the encoding and decoding of the SIP messages which was defined according to the ABNF (Augmented Backus-Naur Form), and implemented the SIP stack. Then, based on SIP stack, achieved the implementation of registration and proxy servers function. For security reasons, this thesis implemented the digest access authentication function, and designed and implemented the registration database.The main work is as follows:(1) The author completed the design and implementation of basic components, It encapsulate the differences between the various platforms. According to the standard SIP protocol, implemented a stateful SIP protocol stack, including syntax and encoding layer, transport layer, transaction layer.(2) Based on ElkSIP protocol stack, achieved the registration and proxy servers. And implemented digest access authentication algorithm to authenticate the user, and used calculated value to save authentication information instead of plaintext, so that can effectively avoid the security issues caused by lost passwords.(3) The protocol stack was tested and verified by using a variety of malformations message testing tool.The project was hosted on googlecode, which was an Open Source project and licensed under the Apache License. This project adopted open source development approach to development. Based on the ELKSIP protocol stack, users could develop a wireless communication system for small and medium enterprise. It’s cost-effective, and independent intellectual property rights of WIPPBX (wireless IPPBX) could meet the communication needs of enterprise real-time communications. Meanwhile, the protocol stack could be used to provide a series of products for the Internet of things applications.