Based On The H.323 Gatekeeper Design And Realization

With the fast development of Internet, IP has become the standard protocols of networks. VoIP technology, based on IP, is being becoming the focus of applications of Internet. Meanwhile, VoIP protocols and standards, the currently researching hotspots, are continuously renovated. H.323, one of the most important VoIP protocols, has been nearly supported by all of VoIP manufacturers, and has a mass of loyal users. The most advantage of H.323 is its maturity, and highest market share. With the development of VoIP technology, H.323 is becoming more mature and sturdy, and showing a strong vitality. Many people believe that H.323 will continue to be the de facto VoIP standard.In this thesis, we discuss the structure of the H.323 stack, functions of main modules of H.323 system, and a typical calling process. Because of the practical values of Authentication and Accounting, it is important to bind the H.323 system and the Radius protocal, which is the actual standart of AAA(Authentication, Authorization, Accounting). We also discuss the structure of the Radius protcoal and give an implementation.In this thesis, we describe the implementation of a gatekeeper based H.323. This gatekeeper is designed for small telecom operators or business customs. It is conformed to the H.323v4 and relevant national standards and ensures interoperability. Besides the functions specified in H.323, such as Address Translation, Admissions Control, Zone Management, Call Management and Bandwidth Control, it can satisfied with the requirements defined by users, such as Web management, dynamic modification of running parameters, NAT environment and AAA(Authentication, Authorization, Accounting) which is based on Radius protocal.Firstly, according to the requirements mentioned above, we provide the module partitions of the gatekeeper, introduce its total design scheme, and explain the functions and interfaces of each module in detail. Secondly, we particularly describe some modules such as gatekeeper kernel module (GKCore), authorization module, and Radius module, and provide some parts of implementing details and important workflows. Lastly, we describe the testing environment for the gatekeeper, provide the testing result cooperating with Cisco gateway, Microsoft Netmeeting, Dialogic gateway, Palm IP phone and Radius Servers, and give suggestions for the future research. Because the gatekeeper is fully conformed to the object oriented designtechnology, it has good scalability and code reusability.