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Chinese universities development of open and distance education, computer technology in the field of deepening the campus network, broadband multimedia voice, video, Internet and other classroom teachers and students have brought great convenience. However, the vast majority of colleges and universities due to the current telephone networks are used by China Telecom or China Unicom's telephone network between institutions at all levels, not established other basic telephone support system. While high communication costs and inefficient communication platform also an urgent need to solve as soon as possible through a technology, Asterisk appearance just can solve these problems. So it is necessary to establish a campus network based on Asterisk phone system. In this paper, Dalian Vocational Technical College of the actual situation, study the campus network based on Asterisk telephone system on campus through existing telephone networks and equipment based on the use of VoIP technology to deliver voice, successfully constructed inside the campus good IP telephone network system and establish a high-efficiency, low-cost communication platform, can effectively improve communication between teachers and students in the school district, at the same time save internal communication costs, but also improve the efficiency of work and study. This paper first describes the basic principles of VoIP and several key technologies, focusing on the analysis of four kinds of mainstream VoIP signaling protocols, also introduced voice codecs, silence suppression and comfort noise generation, echo cancellation, jitter, packet loss compensation and other key technologies, and a comprehensive study of the Asterisk software system, including its architecture, dial plan, install, configure, and some actual cases and testing. Based on in-depth analysis of Dalian Polytechnic campus network and the telephone network status for the main problems and needs, design a campus network based on Asterisk VoIP phone system's overall program, and programs involving hardware devices , software systems, work processes, program design and dial plan number, and how interworking with the PSTN, etc. for a detailed exposition, but also on the design and development of the system was tested, including functional testing, compatibility testing, and performance testing . Finally, according to test results from the voice quality optimization, security, management, three aspects of the campus phone system in the actual operation of a number of key issues were discussed in depth, gives some suggestions and solutions.
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