8,TELECOMMUNICATIONS AND NETWORKS,Chapter,TELECOM TELECOMM,What technologies are used in telecommunications systems? 通信系统使用什么技术？ What telecommunications transmission media should our organization use? 组织中应该使用什么通信传输媒介 How should our organization design its networks?组织应该如何设计网络？,OBJECTIVES,What alternative network services are available to our organization? 对于组织来说什么样的网络服务是可用的 What telecommunications applications can be used for electronic commerce and electronic business?电子商务和电子贸易使用什么通信软件？,OBJECTIVES,Managing LANs 局域网的管理 Managing bandwidth宽带网的管理,MANAGEMENT CHALLENGES,COMPONENTS AND FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM,Telecommunications: Communication of information by electronic means 基于电子方式的信息远程通信 Includes digital data transmission as well as voice transmission 既有数字数据传输也有语音的传输,COMPONENTS AND FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM,Computers to process information 处理信息的计算机 Terminals or any input/output devices that send or receive data 接收或发送数据的终端或输入/输出设备 Communications channels 通信信道 Communications processors 通信处理器 Communications software通信软件,Telecommunications System Components,COMPONENTS AND FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM,Components of a Telecommunications System,Figure 8-1,多路复用器,COMPONENTS AND FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM,Transmit information 传输信息 Establish interface between sender and the receiver 建立接受者和发送者之间的接口 Route messages along most efficient paths通过最有效的线路发送信息,Functions of Telecommunications Systems,COMPONENTS AND FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM,Perform elementary processing of information 完成信息的基本处理 Perform editorial tasks on data 完成数据编辑任务 Convert message speed or format 转换信息的速度和格式 Control flow of information控制信息流,Functions of Telecommunications Systems,COMPONENTS AND FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM,Analog signal 模拟信号Continuous waveform 连续波形 Passes through communications medium 通过通信媒介传送 Used for voice communications用在声音传输,Types of Signals: Analog and Digital,COMPONENTS AND FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM,Digital signal数字信号Discrete waveform离散波形Transmits data coded into two discrete states as 1-bits and 0-bits将数据代码转换为离散状态，0和1Used for data communicationsModemTranslates computers digital signals into analog and vice versa将计算机数字信号转换成模拟信号，反之亦然,Types of Signals: Analog and Digital符号的类型：模拟和数字,COMPONENTS AND FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM,Functions of the Modem,Figure 8-2,COMPONENTS AND FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM,Twisted wire: Telephone systems双绞线：电话系统使用 Coaxial cable: Cable television 同轴电缆：有线电视使用 Fiber optics and optical networks: Dense wave division multiplexing (DWDM)光纤和光学网络：密集波分离多路技术,Communications Channels,COMPONENTS AND FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM,Wireless transmission无线传输: Microwave微波, Satellites人造卫星, Paging systems内存分页, Cellular telephones无线电电话, Personal communication Services个人通信服务, Personal digital assistants个人数字助手, Mobile data networks移动数据网 Transmission speed传输速度: Baud波特, bandwidth带宽,Communications Channels通信信道,COMPONENTS AND FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM,Frequency Ranges for Communications Media and Devices通信设备和介质的频率范围,Figure 8-3,Figure 8-4,COMPONENTS AND FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM,Amocos Satellite Transmission System ：American Oil Company 美国石油公司的卫星传送系统,COMPONENTS AND FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM,Front-end processor: Manages communications for the host computer 前端处理机：处理主机的通信 Concentrator: Collects and temporarily stores messages 集中器：收集和临时存储信息 Controller: Supervises communication traffic控制器：管理通信的交流 Multiplexer: Enables single communication channel to carry data transmissions 多路复用器：授权通信信道只进行数据的传输,Communications Processors and Software,COMMUNICATIONS NETWORKS,Star Network星形网络: All computers and other devices are connected to a central host computer 所有的计算机和设备都被联到主机上星型结构 星型网络：各站点通过点到点的链路与中心站相连。特点是很容易在网络中增加新的站点，数据的安全性和优先级容易控制，易实现网络监控，但中心节点的故障会引起整个网络瘫痪,Network Topologies,A Star Network Topology,COMMUNICATIONS NETWORKS,Figure 8-5,COMMUNICATIONS NETWORKS,Bus Network总线网: Links a number of computers by a single circuit 许多的计算机被联成一个 线型 网络中所有的站点共享一条数据通道。总线型网络安装简单方便，需要铺设的电缆最短，成本低，某个站点的故障一般不会影响整个网络。但介质的故障会导致网络瘫痪，总线网安全性低，监控比较困难，增加新站点也不如星型网容易。,Network Topologies,A Bus Network Topology,COMMUNICATIONS NETWORKS,Figure 8-6,COMMUNICATIONS NETWORKS,Ring Network: All computers are linked by a closed loop 环状结构： 各站点通过通信介质连成一个封闭的环形。环形网容易安装和监控，但容量有限，网络建成后，难以增加新的站点。,Network Topologies,A Ring Network Topology,COMMUNICATIONS NETWORKS,Figure 8-7,Private Branch Exchanges专用交换机Central switching system 中央交换系统Handle firms voice and digital communications处理固定的声音和数字通信,Private Branch Exchanges, Local Area Networks (LANs), and Wide Area Networks (WANs),COMMUNICATIONS NETWORKS,Local Area NetworksRequire their own dedicated channels 需要有自己的专用信道 Encompass a limited distance距离有限 Gateway, router, Network Operating System (NOS), peer-to-peer网关、路由器 网络操作系统，对等系统,Private Branch Exchanges, Local Area Networks (LANs), and Wide Area Networks (WANs),COMMUNICATIONS NETWORKS,COMMUNICATIONS NETWORKS,A Local Area Network (LAN),