Ip Telephony Systems Based On The Gatekeeper Class Design And Implementation,

Since 1990's internet has developed at incredible speed, and now it is playing important role in many fields. It becomes possible that IP network developes towards real-time communication field with the progress of technology. Voice over IP network, namely IP telephone technology, is very welcomed by the market compared with traditional telephone because of its high efficiency in using network, low cost in communication, possibility for various value added functions. The technology has developed rapidly recent years, and has been largely used for the commercial purpose in the world, having a very strong impact on the traditional voice communication. The revolution about voice technology is going, and it predicts a new era that package exchange will take the place of circuit exchange in telecommunications.With the application of IP telephone becoming more and more extensive, some shortages about the traditional IP telephone system began to appear. One of them is that the IP phones registrated in different gatekeeper can not communicate with each other. As far as enlarging the communication capacity of IP phone system in the future to make it become a wide area system with big capacity as PSTN system, this shortage is very harmful. So this dissertation focused on how to resolve the communication problem between the IP phones belonged to different gatekeepers by constructing a gatekeeper hierarchies.This paper firstly discusses the rationale about the IP phone system, then analyzes the structure of H.323 system, finally introduces the design and implement of the gatekeeper hierarchies in H.323 system. The whole paper could be divided into four parts: (1) introduction: chapter 1, introduces the background and prospect of IP phone system development, as well as the main issue of this paper. (2)introduction of basic theory:chapter 2 and 3, in chapter 2 the typical application, communication principle, crucial technology, application advantadge and some problems about IP telephone are discussed; in chapter 3 the components of H.323 IP phone system, RAS, H.225.0 call-controlling protocal are introduced. (3) the part about the implement of the design: chapter 4, talkes about the gatekeeper hierarchies, presenting every signal-controlling procedure of every module, flow chart and important data structure. (4) chapter 5, introduces the implement procedure of a value added functions, namely connect-controlling function, under the gatekeeper hierarchies structure.The soft ware code involved in this article was developed by C++ program language, and has been tested under LINUX system.