计算机概论Cha.ppt

4-1,Chapter 4: Networking and the Internet,4.1 Network Fundamentals 4.2 The Internet 4.3 The World Wide Web 4.4 Internet Protocols 4.5 Security,4-2,Network Classifications,Scope Local Area Network ( LAN, 局域网 ) Metropolitan Area Network (MAN, 城域网) Wide Area Network (WAN, 广域网) Ownership Closed vs. Open ( 封闭式网络 vs. 开放式网络) Topology ( the pattern in which the machines are connected ) Bus (总线型) Ethernet Star (星型) Wireless networks with central Access Point,4-3,Figure 4.1 Network topologies,4-4,Figure 4.1 Network topologies (continued),4-5,Protocols,CSMA/CD（Carrier Sense, Multiple Access with Collision Detection, 带冲突检测的载波侦听多路访问） Used in Ethernet Silent bus provides right to introduce new message CSMA/CA（Carrier Sense, Multiple Access with Collision Avoidance, 带冲突避免的载波侦听多路访问） Used in WiFi Hidden terminal problem,4-6,Figure 4.2 Communication over a bus network,4-7,Figure 4.3 The hidden terminal problem,4-8,Connecting Networks,Repeater（中继器）: Extends a network Bridge（网桥）: Connects two compatible networks Switch（交换机）: Connect several compatible networks Router（路由器）: Connects two incompatible networks resulting in a network of networks called an internet,4-9,Figure 4.4 Building a large bus network from smaller ones,4-10,Figure 4.5 Routers connecting two WiFi networks and an Ethernet network to form an internet,4-11,Inter-process Communication,Client-server（客户机/服务器模型） One server, many clients Server must execute continuously Client initiates communication Peer-to-peer (P2P，对等模型) Two processes communicating as equals Peer processes can be short-lived,4-12,Figure 4.6 The client/server model compared to the peer-to-peer model,4-13,Distributed Systems（分布式系统）,Systems with parts that run on different computers Infrastructure can be provided by standardized toolkits Example: Enterprise Java Beans（企业级JavaBeans） from Sun Microsystems Example: .NET framework（.NET框架） from Microsoft,4-14,The Internet,The Internet: An internet that spans the world Original goal was to develop a means of connecting networks that would not be disrupted by local disasters. Today it has shifted from an academic research project to a commercial undertaking.,4-15,Internet Architecture,Internet Service Provider (ISP, 应特网服务提供商） Tier-1 Tier-2 Access ISP (因特网接入服务提供商): Provides connectivity to the Internet Traditional telephone (dial up connection) Cable connections DSL（Digital Subscriber Line，数字用户线路） Wireless,4-16,Figure 4.7 Internet Composition,4-17,Internet Addressing,IP address（IP地址）: pattern of 32 or 128 bits often represented in dotted decimal notation Mnemonic address: Domain names Top-Level Domains（顶级域名） Domain name system (DNS，域名系统) Name servers DNS lookup Example： 06,4-18,Internet Corporation for Assigned Names & Numbers (ICANN)：因特网名称与数字地址分配机构,Allocates IP addresses to ISPs who then assign those addresses within their regions. Oversees the registration of domains and domain names.,4-19,Traditional Internet Applications,Electronic Mail (E-mail，电子邮件) Domain mail server（邮件服务器） collects incoming mail and transmits outing mail Mail server delivers collected incoming mail to clients via POP3 or IMAP File Transfer Protocol (FTP, 文件传输协议) Telnet（远程登录） and SSH（安全壳）,4-20,More Recent Applications,Voice Over IP (VoIP) Internet Radio（因特网广播） N-unicast（多点广播） Multicast（多路广播）,4-21,World Wide Web,Hypertext（超文本） and HTTP（Hypertext Transfer Protocol，超文本传输协议） Browser（浏览器）gets documents from Web server（Web服务器） Documents identified by URLs（Uniform Resource Locator，统一资源定位器）,4-22,Figure 4.8 A typical URL,4-23,Hypertext Document Format,Encoded as text file HTML（Hypertext Markup Language，超文本标记语言） XML（eXtensible Markup Language，可扩展标记语言）,4-24,Figure 4.12 Package-shipping example,Internet Protocols,4-25,Internet Software Layers,Application layer（应用层）: Constructs message with address Transport Layer（传输层）: Chops message into packets Network Layer（网络层）: Handles routing through the Internet Link（链路层）: Handles actual transmission of packets,4-26,Figure 4.13 The Internet software layers,4-27,Figure 4.14 Following a message through the Internet,4-28,TCP/IP Protocol Suite,Transport Layer TCP（Transmission Control protocol，传输控制协议） UDP（User Datagram Protocol，用户数据报协议） Network Layer IP (IPv4 and IPv6)：Internet Protocol，网际协议,4-29,Figure 4.15 Choosing between TCP and UDP,4-30,Security,Attacks Malware（恶意软件） viruses 病毒, worms 懦虫 Trojan horses 特洛尹木马, spyware (snif