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题名:
多点多媒体通信系统-T120基本应用程序模板及其实现
作者: 邹立
答辩日期: 1997
专业: 计算机软件
授予单位: 中国科学院软件研究所
授予地点: 中国科学院软件研究所
学位: 博士
关键词: 多点 ; 对象 ; 多媒体 ; 线程 ; 同步 ; 消息 ; 事件 ; 会议 ; 信道 ; 令牌 ; 广播
摘要: 近年来,随着微型计算机的功能越来越强大,数字技术在通信网络中的广泛应用,多媒体时代离我们越来越近了。允许多个使用者同时参加,协同工作的多媒体通信系统的快速发展对通信网络,通信协议等都提出了一些新的要求。多媒体会议系统是一种常见的多媒体通信系统,它的功能没有确切的规定,一般来说,一个多媒体会议系统包括白板、文字对话、多点文件传送、多点音频信号和视频信号传送等子系统。多点网络传输协议是实现多媒体会议的基础。在广域网上支持多点数据通信,需要对原有的协议进行扩展或制定新的多点网络传输协议。现有的多点网络传输协议主要有以下三类:基于TCP/IP的多点传输协议、XTP协议、ITU-T T120系统协议 ITU-T T120系列协议是由国际电信联合会电信标准化小组制定的,这些协议包括一系列支持实时、多点数据通信及应用的协议和服务。T120系列协议是专门为异质网络环境下的多媒体通信应用和服务而设计的,它可以在多种不同的网络上实现,例如公共交换电话网(PSTN)、综合业务数字网(ISDN)、电路交换数字网(CSDN)和宽带ISDN网(B-ISDN)。对其它网络的支持,例如局域网(LAN)、TCP/IP和异步传输模式网(ATM)等,也正在考虑或开发。T120系列协议在可靠的点到点传输层连接的基础上,以与底层物理网络无关的方式提供多点通信服务。点到点的传输层连接组合在一个多点通信服务(MCS)域,每个MCS域有效地代表一个“会议”或一个共同的团体活动。在一个MCS域中,不同的逻辑信道可以提供一对一、一对多、多对一的数据分发。基本会议控制模块(GCC)位于MCS之上,提供与多点会议管理有关的服务,这些服务包括会议的建立和综止、加入正在进行的会议、管理会议进行过程中发生的改变、管理会议数据库、管理应用数据库、带宽控制和远地程序激活等。在网络传输中何时采用实时方式或非实时方式由GCC来协调。T120应用层协议使用MCS与GCC服务。ITU定义了几个标准的应用层协议。用户也可以定义自己的应用层协议。只要这些协议都符合T120应用程序模板(即T121)的规定,这些协议就不会互相干扰。T120系列协议中定义了几个应用层协议:可视音频控制标准(T.AVC)、多点二进制文件传送协议(T.MBFT或T.127)、白板和静态图象交换协议(T.SI或T.126)。在各种多点通信协议中,T120系列协议在很多方面有着明显的优点。它可在多种网络环境下应用,已经有较为成熟的标准,而且得到包括微软和Intel等公司在内的许多厂商的支持。本文讨论的是T120系列协议中的T121协议,基本应用程序模板(GAT),的实现。T121为所有的T120应用层协议定义了一个概念性的模型。它为应用程序开发者提供了一个实现模板,从而确保应用层协议开发的一致性。它也指导用户层协议应用程序开发者怎样利用T120的基本结构达到最好的效果。本文讨论了使用对象、同步、线程等技术实现GAT的具体过程。并对这些技术对协议性能的影响作了简要分析。
英文摘要: In these years, along with the tremendous progress of the personal computer and wide application of digital technology in communication network, multimedia age is coming steadily. The rapid developing of multimedia communication system which allow multi-user work cooperatively raise many new demands on communication network and protocol. Multimedia conferencing system is a kind of wide-used multimedia communication system. Its function is not clearly defined but it should include white board, text conversation, multipoint file transfer, multipoint AV information transfer etc. Multipoint network transport protocol is the base of implementation of multimedia conferencing system. In order to support multipoint data communication on WAN, old protocols must be extended or new protocols be applied. The present multipoint network transport protocols fall into 3 categories: TCP/IP based multipoint network transport protocol, XTP protocol, ITU-T T120 series protocol. Established by International Telecommunication Union, ITU-T T120 series protocol contains a series of protocols and services which support real time, multipoint communication application. T120 series protocols is specially designed for the multimedia communication applications and services on heterogeneous networks. They can be realized on many different networks, such as: PSTN, ISDN, CSDN, and B-ISDN. The support for other type of networks such as LAN, TCP/IP and ATM is under consideration. T120 series protocols is based on the reliable point-to-point transport layer connection. It provides multipoint communication services in a physical network independent manner. The combination of point-to-point transport layer connections forms a multipoint communication service (MCS) domain. Every MCS domain effectively represents a "conference" or a common group activity. In a MCS domain, different logic channels can provide one to one, one to many, many to one data delivery.Base on MCS, Generic conference control (GCC) module provides services related to multipoint conference management. These services contains the setting up and termination of conference, joining the ongoing conference, managing changes during conference, management of conference and application database, providing band width control, invoking remote application, etc. GCC coordinates when real time or non real time data transmit should be used. T120 application protocol uses MCS and GCC services. ITU defines several standard application protocols. Users could develop their own application protocols. Provided that they conforms the generic application template of T120 which is specified by T121, these user defined protocols can properly coexist without intervene each other. There are several application protocols in T120 series protocols: audio-visual control protocol (T.AVC), multipoint binary file transfer protocol (T.MBFT or T.127), white board and still image exchange protocol (T.SI or T.126). Compared with other multipoint communication protocols, T120 series have distinct advantages in several aspects. They can be used with various network environments; they have mature standard; and they are supported by many leading company including Microsoft and Intel. This thesis discusses the realization of T121 recommendation in T120 series protocols which defined the generic application template (GAT). T121 provides a conceptual model to all T120 application protocols. GAT is a template for realizing application protocol; it guarantee the consistency of developing. GAT also give a guideline to developers of application protocols which provide the information about how to get the best result with in the T120 infrastructure. The paper discusses the procedure of realizing GAT with technologies such as object, synchronization, thread and also briefly analyzes the affection of adoption of these technologies performance to the performance of the protocol.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.iscas.ac.cn/handle/311060/7036
Appears in Collections:中科院软件所

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Recommended Citation:
邹立. 多点多媒体通信系统-T120基本应用程序模板及其实现[D]. 中国科学院软件研究所. 中国科学院软件研究所. 1997-01-01.
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