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Chapter 2: Technology Infrastructure: The Internet and the World Wide Web Electronic Commerce Objectives In this chapter, you will learn about: • The origin, growth, and current structure of the Internet 因特网的起源、发展和结构 • How packet-switched networks are combined to form the Internet 包交换网络 • How Internet protocols and Internet addressing work 互联网协议 • The history and use of markup languages on the Web 标注语言 Electronic Commerce 2 Objectives (continued) • How HTML tags and links work on the World Wide Web 标签、超链接与WWW • The differences among internets, intranets, and extranets 因特网、内部网与外部网 • Internet2 and the Semantic Web 第二代互联 网与语义网络 Electronic Commerce 3 The Internet and the World Wide Web • Computer network 计算机网络 – Any technology that allows people to connect computers to each other • The Internet 因特网 – A large system of interconnected computer networks spanning the globe • World Wide Web 万维网 – A subset of computers on the Internet Electronic Commerce 4 The history of Computer 1946 Eniac The history of Communication Technology Origins of the Internet 因特网的起源 • Early 1960s – U.S. Department of Defense funded research to explore creating a worldwide network • In 1969 – Defense Department researchers connected four computers into a network called ARPANET • Throughout the 1970s and 1980s – Academic researchers connected to ARPANET and contributed to its technological developments • In 1991, the NSF: – Eased restrictions on commercial Internet activity – Began implementing plans to privatize the Internet Electronic Commerce 7 Growth of the Internet Electronic Commerce 8 Emergence of the World Wide Web 万维网的兴起 • The Web – Software that runs on computers connected to the Internet • Hypertext server: 超文本服务器 – Stores files written in the hypertext markup language – Lets other computers connect to it and read files • Hypertext Markup Language (HTML) 超文本标识语言 – Includes a set of codes (or tags) attached to text Electronic Commerce 9 Packet-Switched Networks 包交换网络 • Local area network (LAN) 局域网 – Network of computers located close together • Wide area networks (WANs) 广域网 – Networks of computers connected over greater distances • Circuit 线路 – Combination of telephone lines and closed switches that connect them to each other • Circuit switching 线路交换 – Centrally controlled, single-connection model Electronic Commerce 10 Packet-Switched Networks (continued) • Packets 数据包 – Files and e-mail messages on a packet-switched network are broken down into small pieces, called packets – Travel from computer to computer along the interconnected networks until they reach their destinations Electronic Commerce 11 Routing Packets 路由数据包 • Routing computers 路由计算机 – Computers that decide how best to forward packets • Routing algorithms 路由算法 – Rules contained in programs on router computers that determine the best path on which to send packets Electronic Commerce 12 Electronic Commerce 13 Internet Protocols 互联网协议 • Protocol 协议 – Collection of rules for formatting, ordering, and error-checking data sent across a network • TCP 传输控制协议 – Controls disassembly of a message or a file into packets before transmission over the Internet – Controls reassembly of packets into their original formats when they reach their destinations • IP 互联网IP协议 – Specifies addressing details for each packet Electronic Commerce 14 IP Addressing and Domain Names IP Addressing IP地址 • Internet Protocol version 4 (IPv4) – Uses a 32-bit number to identify computers connected to the Internet Domain Names 域名 • A domain name is a set of words assigned to a specific IP address • Top-level domain (or TLD) 顶级域名 – Rightmost part of a domain name Electronic Commerce 15 Electronic Commerce 16 Electronic Mail Protocols 电子邮件协议 • Electronic mail (e-mail) – Must be formatted according to a common set of rules • Simple Mail Transfer Protocol (SMTP) 简单邮件传输 协议 – Specifies the format of a mail message • Post Office Protocol (POP) 邮局协议 – POP messages can tell the e-mail server to: • Send mail to a user’s computer and delete it from the email server • Send mail to a user’s computer and not delete it • Simply ask whether new mail has arrived Electronic Commerce 17 Markup Languages and the Web • Text markup language 文本标识语言 – Specifies a set of tags that are inserted into text • Hypertext Markup Language (HTML) is the prevalent markup language used to create documents on the Web today 超文本标识语言使用最广泛 • HTML tags are interpreted by a Web browser and are used by it to format the display of the text 由浏览器解 释并展示 • HTML links can be structured as: 超链接 – Linear hyperlink structures 线性结构 – Hierarchical hyperlink structures 层次结构 Electronic Commerce 18 Extensible Markup Language (XML) 可扩展标识语言 • XML includes data management capabilities that HTML cannot provide 提供HTML不具备的数据管理能力 • Differences between XML and HTML: – XML is not a markup language with defined tags XML不是已定义标记的标注语言 – XML tags do not specify how text appears on a Web page XML的标记不是用来指定格式,而是用 来表示信息的含义(语义) Electronic Commerce 19 Intranets and Extranets 内部网与外部网 • Intranet 内部网 – Interconnected network that does not extend beyond the organization that created it • Extranet 外部网 – Intranet extended to include entities outside the boundaries of an organization – Connects companies with suppliers, business partners, or other authorized users Electronic Commerce 20 Public and Private Networks • Public network 公共网络 – Any computer network or telecommunications network available to the public • Private network 专用网络 – A private, leased-line connection between two companies that physically connects their intranets Electronic Commerce 21 Virtual Private Network (VPN) • VPN 虚拟专用网 – An extranet that uses public networks and their protocols • IP tunneling IP通道 – Effectively creates a private passageway through the public Internet • Encapsulation 封装 – Process used by VPN software • VPN software VPN软件 – Must be installed on the computers at both ends of the transmission Electronic Commerce 22 Electronic Commerce 23 Internet Connection Options 因特网接入方式 • Bandwidth 带宽 – Amount of data that can travel through a communication line per unit of time • Net bandwidth 实际带宽 – Actual speed that information travels • Broadband connections 宽带接入 – Broadband connections operate at speeds of greater than 200 Kbps 超过200 Kbps 的接入 Electronic Commerce 24 Wireless Connections 无线接入 • Bluetooth 蓝牙技术 – Designed for personal use over short distances 距离短 – Low-bandwidth technology, with speeds of up to 722 Kbps 带宽低 – Networks are called personal area networks (PANs) or piconets 个人区域网或微微网 – Consumes very little power 能耗低 – Devices can discover each other and exchange information automatically 自动搜索和信息交换 Electronic Commerce 25 Wireless Ethernet (Wi-Fi) 无线以太网 • Wireless Ethernet (Wi-Fi or 802.11b) is the most common wireless connection technology for use on LANs 局域网中最常用 的无线接入技术 • Wireless access point (WAP) 无线访问点 – Device that transmits network packets between Wi-Fi-equipped computers and other devices • Has a potential bandwidth of 11 Mbps and a range of about 300 feet • Devices are capable of roaming 可支持漫游 Electronic Commerce 26 Cellular Telephone Networks 移动电话网络 • Third-generation (3G) cell phones 3G手机 – Combine the latest technologies available today • Short message service (SMS) 短消息服务 – Protocol used to send and receive short text messages • Mobile commerce (m-commerce) 移动商务 – Describes the kinds of resources people might want to access using wireless devices Electronic Commerce 27 Internet2 and the Semantic Web 第二代互联网与语义网 • Internet2 第二代互联网 – Experimental test bed for new networking technologies – Has achieved bandwidths of 10 Gbps and more on parts of its network – Used by universities to conduct large collaborative research projects • Semantic Web 语义网 – Project by Tim Berners-Lee – If successful, it would result in words on Web pages being tagged (using XML) with their meanings Electronic Commerce 28 Summary • TCP/IP TCP/IP协议 – Protocol suite used to create and transport information packets across the Internet • POP, SMTP 电子邮件协议 – Protocols that help manage e-mail • Hypertext Markup Language (HTML) and Extensible Markup Language (XML) 标注语言 Electronic Commerce 29 Summary (continued) • Intranets 内部网 – Private internal networks • Extranet 外部网 – Used when companies want to collaborate with suppliers, partners, or customers • Internet2 第二代互联网 – Experimental network built by a consortium of research universities and businesses Electronic Commerce 30