| The rapid development of VoIP technology and services has made a deep affection to the traditional telephony service, especially to the International or National Direct Call service. How to setup one set of VoIP network architecture and to develop the VoIP devices suitable for our country have been the value questions. In this paper, the design and implementation of UESTC IPG-2000A IP TELEPHONY GATEWAY, one of the VoIP projects of the Ministry of Information Industry, is discussed.Firstly, H.323 protocol-the recommendation that describes how to provide multimedia communications services over Packet-Based Networks is introduced in this paper. The structure of protocol stack and the components of the H.323 system are mainly discussed. Now H.323 protocol has become the leading standard of VoIP, because it measures up the technical requirements of IP telephony. In the following parts, some other protocols of VoIP including SIP, MGCP, H.248/MEGACO and the soft switch technical are analyzed. The Dialogic Company's DM3/IPLink board used in the gateway system, there is an elaborate analysis of the DM3 CT platform including function, programming interface, programming model and the way of the data communication. And then the actual gateway system is described in this paper. Its designing thoughts and partly implementations such as call control and process, network agent, database accessing interface and so on are presented. Its test results are described, which include function test, performance test, call procedure test, communication with other manufacturer's devices test. At last, an advanced system is put forward. |
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