Chapter 5 Internet
计算机网络(第5版),清华大学出版社,严伟潘爱民 译ppt Chapter1-Introduction
.
33
Critique of the OSI Model and Protocols
• Bad timing. • Bad technology. • Bad implementations. • Bad politics.
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OSI Model Bad Timing
The apocalypse of the two elephants.
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12
Metropolitan Area Networks
A metropolitan area network based on cable TV.
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Wide Area Networks (1)
WAN that conne. cts three branch offices in Australia 14
The philosoph. er-translator-secretary architecture 19
Protocol Hierarchies (3)
Example information flow supporting virtual
c. ommunication in layer 5.
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The reference model used in this book.
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Comparison of the OSI and TCP/IP Reference Models
Concepts central to OSI model • Services • Interfaces • Protocols
Combinations of wireless networks and mobile computing
《跨境电商实用英语》全套教学课件Unit 3-Chapter 5 SNS Marketing
2
Learn the relative words and expressions
3
Understand the procedure of promoting online store and products on social
networking sites, such as Facebook, Instagram and Pinterest
PART ONE
Warming-up
PART 1 Warming-up
Task: In general, store marketing is divided into platforminside marketing and platform-outside marketing. Look at the following product page, and discuss with a partner about what platform-inside and platform-outside marketing tools are used and how they help to bring more customers and transactions to the store.
On a global scale, the most popular social media sites include Facebook, Twitter, Instagram, Pinterest, Youtube, VK, LinkedIn and so on.
PART 2 Passage Reading
数据仓库 Chapter 5 定义商业需求
• 信息包：酒店入住
– 信息主题：酒店客户占用情况 » 维度（层次结构/分类）：时间、酒店、房间类型 » 事实：已占用房间、空房间、入住人数、收入
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厦门大学软件学院
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Chapter Five 定义商业需求
• Contents
– 维度分析 – 信息包 – 收集需求的方法 – 需求定义
厦门大学软件学院
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信息包（续）
• 不完全确定的需求（续）
– 一个信息包 – 信息包的作用
• • • • • • •
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信息主题：销售分析
维度
层 次 结 构
定义主题 设计关键业务指标 建立数据粒度 估计数据仓库的规模 决定数据更新的频率 确定如何将信息打包 …
时间 年
地点 国家
产品 类
数据仓库
Chapter Five 定义商业需求
Contents
– 维度分析 – 信息包 – 收集需求的方法 – 需求定义
2013-12-20
厦门大学软件学院
2
Chapter Five 定义商业需求
• 数据仓库是一个信息传递系统 • 大多数DW的开发者都有OLTP开发的背景， 思维模式的转变 • 用户关于DW的视角也与OLTP不同 • 需求定义阶段主要考虑的问题在于：用户 需要哪些信息，而非我们如何去提供这样 的信息
• 如何对数据仓库的项目进行分析？
2013-12-20
厦门大学软件学院
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维度分析（续）
• 商业数据的维度
– 管理者从商业维度的角度来看待商业问题
用户 能够 给你 描述 这些 商业 维度 ，我 们能 找到 这些 商业 维度
市场部长 市场经理 财务经理
《演讲的艺术》chapter1-5课后summary
One of your first assignments will be to present an introductory speech, either a speech of self-introduction or a speech introducing a classmate. Focus the speech on a limited number of ideas and be creative in developing them. Use interesting supporting materials and present them in colorful, descriptive language.
Chapter2speakingconfidentlyandethically
stage fright is an issue for public speakers in all countries. Rather than trying to eliminate every trace of stage fright, you should try to transform it into positive energy. To some extent, this will happen naturally as you gain experience as a speaker, but you should also think positively, prepare thoroughly, visualize yourself giving a successful speech, remember that most nervousness is not visible to the audience, and think of your speech as communication rather than as a performance in which you must do everything perfectly
计算机网络英文题库(附答案)chapter
Chapter 1 Computer Networks and the Internet1．The ( ) is a worldwide computer network, that is, a network that interconnects millions of computing devices throughout the world. ppt3A public InternetB IntranetC switch netD television net2．Which kind of media is not a guided media? ( )A twisted-pair copper wireB a coaxial cableC fiber opticsD digital satellite channel3．Which kind of media is a guided media? ( )A geostationary satelliteB low-altitude satelliteC fiber opticsD wireless LAN4．The units of data exchanged by a link-layer protocol are called ( ).A FramesB SegmentsC DatagramsD bit streams5．Which of the following option belongs to the circuit-switched networks? ( )A FDMB TDMC VC networksD both A and B6．( )makes sure that neither side of a connection overwhelms the other side by sending too many packets too fast.A Reliable data transferB Flow controlC Congestion controlD Handshaking procedure7．( ) means that the switch must receive the entire packet before it can begin to transmit the first bit of the packet onto the outbound link.A Store-and-forward transmissionB FDMC End-to-end connectionD TDM8．Datagram networks and virtual-circuit networks differ in that ( ).A datagram networks are circuit-switchednetworks, and virtual-circuit networks arepacket-switched networks.B datagram networks are packet-switchednetworks, and virtual-circuit networks arecircuit-switched networks.C datagram networks use destinationaddresses and virtual-circuit networks useVC. numbers to forward packets toward theirdestination.D datagram networks use VC. numbers andvirtual-circuit networks use destinationaddresses to forward packets toward theirdestination.9．In the following options, which one is not a guided media? ( )A twisted-pair wireB fiber opticsC coaxial cableD satellite10．Processing delay does not include the time to ( ).A examine the packet’s headerB wait to transmit the packet onto the linkC determine where to direct the packetD check bit-error in the packet11．In the following four descriptions, which one is correct? ( )A The traffic intensity must be greater than1.B The fraction of lost packets increases asthe traffic intensity decreases.C If the traffic intensity is close to zero,the average queuing delay will be close tozero.D If the traffic intensity is close to one,the average queuing delay will be close toone.12．The Internet’s network layer is responsible for moving network-layer packets known as ( ) from one host to another.A frameB datagramC segmentD message13．The protocols of various layers are called ( ).A the protocol stackB TCP/IPC ISPD network protocol14．There are two classes of packet-switched networks: ( ) networks and virtual-circuit networks.A datagramB circuit-switchedC televisionD telephone15．Access networks can be loosely classified into three categories: residential access, company access and ( ) access.A cabledB wirelessC campusD city areaQuestion 16～17Suppose, a is the average rate at which packets arrive at the queue, R is the transmission rate, and all packets consist of L bits, then the traffic intensity is ( 16 ), and it should no greater than ( 17 ).16． A LR／aB La／RC Ra／LD LR／a17．A 2B 1C 0D -118．In the Internet, the equivalent concept to end systems is ( ).A hostsB serversC clientsD routers19．In the Internet, end systems are connected together by ( ).A copper wireB coaxial cableC communication linksD fiber optics20．End systems access to the Internet through its ( ).A modemsB protocolsC ISPD sockets21．End systems, packet switches, and other pieces of the Internet, run ( ) that control thesending and receiving of information within the Internet.A programsB processesC applicationsD protocols22．There are many private networks, such as many corporate and government networks, whose hosts cannot exchange messages with hosts outside of the private network. These private networks are often referred to as ( ).A internetsB LANC intranetsD WAN23．The internet allows ( ) running on its end systems to exchange data with each other.A clients applicationsB server applicationsC P2P applicationsD distributed applications24．The Internet provides two services to its distributed applications: a connectionlessunreliable service and () service.A flow controlB connection-oriented reliableC congestion controlD TCP25．It defines the format and the order of messagesexchanged between two or more communicatingentities, as well as the actions taken on the transmission and/or receipt of a message orother event. The sentence describes ( ).A InternetB protocolC intranetD network26．In the following options, which does not define in protocol? ( )A the format of messages exchanged betweentwo or more communicating entitiesB the order of messages exchanged betweentwo or more communicating entitiesC the actions taken on the transmission ofa message or other eventD the transmission signals are digitalsignals or analog signals27．In the following options, which is defined in protocol? ( )A the actions taken on the transmission and/orreceipt of a message or other eventB the objects exchanged between communicating entitiesC the content in the exchanged messagesD the location of the hosts28．In the following options, which does not belong to the network edge? ( )A end systemsB routersC clientsD servers29．In the following options, which belongs to the network core? ( )A end systemsB routersC clientsD servers30．In the following options, which is not the bundled with the Internet’sconnection-oriented service? ( )A reliable data transferB guarantee of the transmission timeC flow controlD congestion-control31．An application can rely on the connection to deliver all of its data without error and in the proper order. The sentence describes ( ).A flow controlB congestion-controlC reliable data transferD connection-oriented service32．It makes sure that neither side of a connection overwhelms the other side by sending too many packets too fast. The sentence describes ( ).A flow controlB congestion-controlC connection-oriented serviceD reliable data transfer33．It helps prevent the Internet from entering a state of gridlock. When a packet switch becomes congested, its buffers can overflow and packet loss can occur. The sentence describes ( ).A flow controlB congestion-controlC connection-oriented serviceD reliable data transfer34．The Internet’s connection-oriented service has a name, it is ( ).A TCPB UDPC TCP/IPD IP35．In the following options, which service does not be provided to an application by TCP?( )A reliable transportB flow controlC video conferencingD congestion control36．The Internet’s connectionless service is called ( ).A TCPB UDPC TCP/IPD IP37．In the following options, which does not use TCP?( )A SMTPB internet telephoneC FTPD HTTP38．In the following options, which does not use UDP?( )A Internet phoneB video conferencingC streaming multimediaD telnet39．There are two fundamental approaches to buildinga network core, ( ) and packet switching.A electrical current switchingB circuit switchingC data switchingD message switching40．In ( ) networks, the resources needed along a path to provide for communication between the end system are reserved for the duration of the communication session.A packet-switchedB data-switchedC circuit-switchedD message-switched41．In ( ) networks, the resources are not reserved;a session’s messages use the resources ondemand, and as a consequence, may have to wait for access to communication link.A packet-switchedB data-switchedC circuit-switchedD message-switched42．In a circuit-switched network, if each link has n circuits, for each link used by the end-to-end connection, the connection gets ( ) of thelink’s bandwidth for the duration of theconnection.A a fraction 1/nB allC 1/2D n times43．For ( ), the transmission rate of a circuit is equal to the frame rate multiplied by the number of bits in a slot.A CDMAB packet-switched networkC TDMD FDM44．( ) means that the switch must receive the entire packet before it can begin to transmit the first bit of the packet onto the outbound link.A Queuing delayB Store-and-forward transmissionC Packet lossD Propagation45．The network that forwards packets according to host destination addresses is called ( )network.A circuit-switchedB packet-switchedC virtual-circuitD datagram46．The network that forwards packets according to virtual-circuit numbers is called ( ) network.A circuit-switchedB packet-switchedC virtual-circuitD datagram47．In the following entries, which is not a kind of access network?( )A residential accessB company accessC wireless accessD local access48．Suppose there is exactly one packet switch between a sending host and a receiving host. The transmission rates between the sending host and the switch and between the switch and thereceiving host are R1 and R2, respectively.Assuming that the switch uses store-and-forward packet switching, what is the total end-to-end delay to send a packet of length L? (Ignorequeuing delay, propagation delay, andprocessing delay.) ( )A L/R1＋L/R2B L/R1C L/R2D none of the above49．The time required to examine the packet’s headerand determine where to direct the packet is part of the ( ).A queuing delayB processing delayC propagation delayD transmission delay50．The time required to propagate from the beginning of the link to the next router is ( ).A queuing delayB processing delayC propagation delayD transmission delay51．Consider sending a packet of 3000bits over a path of 5 links. Each link transmits at 1000bps. Queuing delays, propagation delay and processing delay are negligible. (6 points)(1).Suppose the network is a packet-switched virtual circuit network. VC setup time is 0.1 seconds. Suppose the sending layers add a total of 500 bits of header to each packet. How long does it take to send the file from source to destination?(2).Suppose the network is a packet-switched datagram network and a connectionless service is used. Now suppose each packet has 200 bits of header. How long does it take to send the file?(3).Suppose that the network is a circuit-switched network. Further suppose that the transmission rate of the circuit between source and destination is 200bps. Assuming 0.02s setup time and 200 bits of header appended to the packet, how long does it take to send the packet?Solution:?(1) .?t=5*(3000+500)/1000+0.1=17.6s?(2). t=5*(3000+200)/1000=16s(3). t=(3000+200)/200+0.02=16.02s。
第一章 WAN 简介_1_CN
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1.3 WAN 连接方案
ITE I Chapter 6
© 2006 Cisco Systems, Inc. All rights reserved.
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1.3.1 WAN 链路连接方案 WAN 解决方案的实施有许多方案。各种方案之 间存在技术、速度和成本方面的差异。
Cisco Public
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1.1.3 不断拓展的网络模型
分层网络模型是一套行之有效的高级工具，可用 来设计可靠的网络基础架构。
它提供网络的模块化视图，从而方便设计和构建 可扩展的网络。.
ITE 1 Chapter 6
© 2006 Cisco Systems, Inc. All rights reserved.
ITE 1 Chapter 6
© 2006 Cisco Systems, Inc. All rights reserved.
Cisco Public
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1.2.4 WAN 交换概念
分组交换网络
ITE 1 Chapter 6
© 2006 Cisco Systems, Inc. All rights reserved.
Cisco Public
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1.1.3不断拓展的网络模型
ITE 1 Chapter 6
© 2006 Cisco Systems, Inc. All rights reserved.
Cisco Public
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1.2 WAN 技术概念
ITE I Chapter 6
© 2006 Cisco Systems, Inc. All rights reserved.
2024版《计算机网络基础》完整版课件全书电子教案pdf
通过确认应答、超时重传、流量控制等机制 实现。
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UDP协议
UDP协议的特点
无连接、不可靠传输、基于数据报。
UDP的适用场景
适用于实时性要求高、可容忍少量丢包的应 用，如音视频通话、实时游戏等。
UDP的报文格式
UDP的传输效率
包括源端口号、目的端口号、长度和校验和 等字段。
由于没有TCP的确认应答等机制，UDP的传 输效率相对较高。
将网络的通信过程划分为小一些、简 单一些的部件，有助于各个部件的开 发、设计和故障排除。
2024/1/29
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OSI七层模型
物理层
负责传输比特流，提供为建立、 维护和拆除物理链路所需要的机 械的、电气的、功能的和规程的
特性。
2024/1/29
数据链路层
负责将比特组合成字节，再将字节 组合成帧，使用链路层地址（以太 网使用MAC地址）来访问介质， 并进行差错检测。
应用层
为操作系统或网络应用程序提供访问网络服务的 接口。
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TCP/IP四层模型
对应于OSI的网络层，负责将网 络地址翻译成对应的物理地址， 并决定如何将数据从发送方路由 到接收方。
对应于OSI的会话层、表示层和 应用层三层，为操作系统或网络 应用程序提供访问网络服务的接 口。
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网络接口层 网络层 传输层 应用层
2024/1/29
CIDR技术
无类别域间路由，实现IP地址的聚合和路由 的简化。
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路由选择算法与路由协议
路由选择算法
静态路由选择算法和动态路由选择算 法，根据网络拓扑和流量变化进行路 由选择。
路由协议
RIP、OSPF、BGP等，用于路由器之 间交换路由信息，建立和维护路由表。
中国文化概况(修订版)Chapter-5
Ancient Science and Technology
Four Great Inventions Traditional Chinese Medicine Other Impressive Ancient Inventions
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Traditional Chinese Medicine
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Other Impressive Ancient Inventions
Porcelain
• made generally from clay • heated at a high degree • the first glazing color is blue
Abacus
• an early form of calculator
compass
printing
gunpowder
paper-making
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Four Great Inventions
Compass
• shows geographic directions • use the earth’s magnetic field • enables international trade and exploration • denotes eight main directions • helpful for the explorations of Zheng
13
Four Great Inventions
Printing
• known as “mother of civilization” • includes block printing and movable type printing • block printing is time-consuming and the blocks become useless after the printing • movable type printing is more convenient with the pieces being durable and reusable