【作者】 范文强；

【导师】 黄桂金；

【作者基本信息】 华中科技大学 ， 通信与信息系统， 2004， 硕士

【摘要】 由于分组交换的IP网络特别是Internet的飞速发展,与IP网络相关的技术也取得了巨大的进展。基于包交换网络的可视通信系统成为研究人员和电信、网络及计算机厂商关注的焦点之一。集语音、文字和图像于一体的IP网络的可视通信系统是其中的热点之一。因此,对基于IP网络的可视通信系统进行研究有积极意义。本文首先简要概述了可视通信及其发展,并介绍了H.323协议栈结构和系统结构,对H.225.0协议进行了分析。接着结合课题研究,介绍了H.323可视通信系统软件终端的总体方案设计,以及简介了独立于任何操作系统和硬件外设的H.323协议栈软件。然后,分析了本人负责开发的H.225.0协议,给出了呼叫接纳(RAS——Registration,Admission and Status)和呼叫信令两个任务的详细设计及其软件实现。最后论述了呼叫接纳和呼叫处理模块的测试以及得出的结论。H.225.0协议主要实现两个功能,其一是对RAS协议功能的实现,完成网守搜寻、端点登记、呼叫接纳和带宽管理等功能;其二是实现H.225.0呼叫信令协议的功能,建立H.245媒体控制信道,或者通过快速连接和隧道机制,建立一条或多条逻辑信道。H.225.0协议的设计实现有其特殊的困难,一是要对RAS消息和呼叫信令消息进行ASN.1编码;二是设计有限状态机结构实现呼叫信令模块;三是快速连接和隧道技术两种新机制的实现。因此,在软件设计和代码实现上要对这些进行重点考虑。更多还原

【Abstract】 The Internet developed very quickly. It provides the basement of computer network technology for the implement of the visual communication system. The system is a multimedia communication system that can transport audio、video and data information over IP network, and is the one of focus that people study visual communication system. First, this thesis summarizes the development history and direction of visual communication. Then introduces H.323 protocol stack and system structure firstly, and analyzes H.225.0 protocol. Subsequently, base on these, it introduces the general software scheme of H.323 visual communication system software terminal, and the implementation of H.323 protocol stack independent of any operation system and hardware. Then it gives the detailed design and software realization of RAS and call signalling modules. At last, it expatiates the test and results for these two modules.There are two main functions in H.225.0 protocol. One is to realize RAS signalling protocol, and to complete gatekeeper discovery、endpoint registration、admissions 、bandwidth change, and so on. The other is to realize call signalling protocol, that is to establish H.245 media control channel, or by fast connect procedure and Tunnelling mechanism to establish one or more logical channels.There are some special difficulties on the design of H.225.0 protocol. One is the ASN.1 encoding for RAS and call signalling messages. Another is the implementation for call signalling module by FSM(finite state machine). The last is implementation for Fast Connect and Tunnelling two new mechanisms. These difficulties must be taken into account in the course of design of software and coding.更多还原