Transcript Chapter 1: Introduction to Electronic Commerce

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
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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
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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
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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
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Growth of the Internet
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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
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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
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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
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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
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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
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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
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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
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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
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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）
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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