计算机网络第五版(英文版).ppt

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1、Computer NetworksThe course is a part of the Excellent Course Program(1)Review last lectureRandomly choose students to answer some questions,and record the grade.Discuss some interesting topicsOne 10 students per group One of them makes a presentationWrite short reports and answer the problems after

2、 each chaptersEach student must do themRecord the gradeExperimentsIn Computer Networks LabThe course is a part of the Excellent Course Program(2)Total point(Note that the final grade components may change!)Final exam(40%),middle exam(20%),experiments(20%),reports/problems(10%),and others(10%)After s

3、tudy Chapter 4,there will be mid-term examExploring StudySome subjects for exploring studyIf you have novel idea,you will get bonus points.The course is a part of the Excellent Course Program(3)Welcome to our research lab（1）网络传输中流媒体QoE 保障理论与方法研究（NSFC：61073154）P2P网络中语义场模型及关键技术研究（Applying NSFC project

4、）Mobile Cloud Computing Platform for Real Time Business Intelligence ApplicationsCo-operator:The Hong Kong Polytechnic UniversityApplying Doctor foundation in MOEThe course is a part of the Excellent Course Program(4)Welcome to our research lab（2）物联网高速接入和应用技术Co-operator:EPFL正申请上海市科委项目 This is a Bili

5、ngual CourseWhy we give this bilingual course?To meet the needs of excellent engineer training program and internationalizationOur aimText book,exercises,test,and examination will be 100%in English.PPT will exceed 95%in EnglishGiving the lecture and discussion will be more then 60%in EnglishIt is im

6、portant to ensure the quality of teaching.We will gradually increase the percentage of English language.ReferenceText Book:Andrew S.Tanenbaum,David J.Wetherall,“Computer Networks”,5th Ed.,2010,Addison-Wesley.James F.Kurose,Keith W.Ross,“Computer Networks:A Top-Down Approach”,5th Ed.,2010,Addison-Wes

7、ley.Larry L.Peterson,Bruce S.Davie,“Computer Networks:A System Approach”,5th Ed.,2011,Elsevier.高传善等著，计算机网络教程，1994，复旦大学出版社。ReferenceDouglas Comer,“Internetworking With TCP/IP volume 1:Principles,Protocols,and Architecture”,5th Ed.,2006,Pearson.Andrew S.Tanenbaum,Maarten Van Steen,“Distributed Systems

8、:Principles and Paradigms”,2nd Ed.,2008,Pearson.Some papersIETF RFCsThe Most Important Journals IEEE-ACM Transaction on Networking：Bimonthly，ISSN:1063-6692IEEE NETWORK：Bimonthly，ISSN:0890-8044The Most Important Conferences ACM SIGCOMM：IEEE Infocom：ACM SIGMETRICS：China Computer FederationEvaluating a

9、cademic achievementClass A is top important of journal and conferenceClass B is very important of journal and conference Class C is important of journal and conferenceWebsites and online courses IntroductionChapter 11.1 What Is Computer NetworksComputer networks are collections of autonomous compute

10、rs,e.g.,the InternetComputer Networks vs.Distributed SystemsThe key distinction is software systems,especially OS.Complex NetworksScale-free networksSmall-world networks Source:Albert-Lszl Barabsi,“The physics of the Web”,Physics World 14,(2001)Source:David Lazer et al.,“Computational Social Science

11、”,SCIENCE,323,721-724(2009)Exploring Study(1)1.Use complex network theory and dynamics of human behavior(DHB)to analyze social networks and optimize social networking service(SNS).2.Research on opinion evolution and interference model on Internet,specially on social networking service(SNS).1.2 Uses

12、of Computer Networks(1)Computer Cluster A computer cluster consists of a set of loosely connected computers that work together so that in many respects they can be viewed as a single system.From Wikipedia1.2 Uses of Computer Networks(2)Cloud Computing(1)From WikipediaInfrastructure as a Service(IaaS

13、)Platform as a Service(PaaS)Software as a Service(SaaS)1.2 Uses of Computer Networks(3)Cloud Computing(2)ArchitectureFrom Wikipedia1.2 Uses of Computer Networks(4)Cloud Computing(3)Deployment ModelsPrivate Cloud Community CloudPublic CloudHybrid CloudSource:Wikipedia1.2 Uses of Computer Networks(5)C

14、lient-server moduleThe Network maybe VPN which is over InternetProvide many services over the networkThe Web is an example of client-server computing.E-commerceRequestReply1.2 Uses of Computer Networks(6)Triple-Play Networks(1)青海省公检法信息通信网为例IconRouter1.2 Uses of Computer Networks(7)Triple-Play Networ

15、ks(2)Switch1.2 Uses of Computer Networks(8)Triple-Play Networks(3)1.2 Uses of Computer Networks(9)Peer-to-Peer NetworksThey are overlay networksThere are no fixed clients and servers1.2 Uses of Computer Networks(10)The Category of Network Use(1)Resource sharingPerson-to-person communicationVoIP,vide

16、o conferenceDesktop sharingInstant messaging,like Skype,MSN,QQ,etc.Blog,TwitterWiki,like Wikipedia,etc.E-commerce,includes online auctionsEntertainment,like MP3,IPTV,games,etc.1.2 Uses of Computer Networks(11)The Category of Network Use(2)Ubiquitous computing(Ubicomp,普适计算)/Ubiquitous networks(Ubinet

17、,泛在网络)Wireless Sensor networks(WSN)Power-line networksRFID(Radio Frequency IDentification)Internet of things(IOT,物联网)UbinetIOTWSNSource:WikipediaSource:邬贺铨,中国下一代互联网的研究和CNGI项目1.2 Uses of Computer Networks(12)Wireless Networks and Mobile ComputingWiFi,cellular networks,WSN,etc.Sensor networks can be b

18、uilt with ZigBee,WiFi,etc.Smart phonesGPSM-commerceWearable computersSource:Wikipedia1.3 Network Hardware(1)Transmission technologyPoint-to-point linksIt is Important to find good route from the source to the destination.UnicastingBroadcast linksBroadcasting,multicasting1.3 Network Hardware(2)Networ

19、ks can be classified by their scaleScaleTypeVicinityPAN(Personal Area Network)Building/CampusLAN(Local Area Network)CityMAN(Metropolitan Area Network)CountryWAN(Wide Area Network)PlanetThe Internet(network of all networks)1.3.1 Personal Area NetworkConnect devices over the range of a personPAN can b

20、e built with Bluetooth,ZigBee,or RFID1.3.2 Local Area NetworkConnect devices in a home or office buildingCalled enterprise network in a companyHow the sharing communication channel is allocated?1.3.3 Metropolitan Area NetworkExample MAN based on cable TVWiMAX1.3.4 Wide Area Network(1)Subnet is colle

21、ction of lines and routersThe transmission line may own lines or lease SDH linksExample WAN connecting three branch officesTag router switch/Multi-service switch router(MSR)1.3.4 Wide Area Network(2)A VPN(Virtual Private Network)is a WAN built from virtual links that run on top of the Internet.1.3.4

22、 Wide Area Network(3)An ISP(Internet Service Provider)network is also a WAN.Routing algorithmForwarding algorithm1.3.4 Wide Area Network(4)Make use of wireless technologiesSatellite systemsCellular telephone network1.3.5 InternetworkingInternet vs.internetSubnet workGatewayProblems4,5,7,8,91.4 Netwo

23、rk SoftwareProtocol layersDesign Issues for the LayersConnection-Oriented vs.ConnectionlessService PrimitivesRelationship of Services to Protocols1.4.1 Protocol layers(1)Protocol layering is the main structuring method used to divide up network functionality.Each layer communicates only by using the

24、 one belowLower layer services are accessed by an interfaceAt bottom,messages are carried by the mediumEach protocol instance talks virtually to its peerVirtual communication Physical communication1.4.1 Protocol layers(2)Each lower layer adds its own header(with control information)to the message to

25、 transmit and removes it on receiverLayers may also split and join messages,etc.1.4.1 Protocol layers(3)Information transmission unit1.4.2 Design Issues for the LayersEach layer solves a particular problem but must include mechanisms to address a set of recurring design issuesIssueExample mechanisms

26、 at different layersReliability despite failuresCodes for error detection/correction(3.2,3.3)Routing around failures(5.2)Network growth and evolutionAddressing(5.6)and naming(7.1)Protocol layering(1.3)Allocation of resources like bandwidth Multiple access(4.2)Congestion control(5.3,6.3)Security agai

27、nst various threatsConfidentiality of messages(8.6)Web security(8.9)1.4.3 Connection-Oriented vs.Connectionless(1)Connection-oriented,must be set up for ongoing use(and torn down after use),e.g.,phone callConnectionless,messages are handled separately,e.g.,postal delivery1.4.3 Connection-Oriented vs

28、.Connectionless(2)In connection-oriented serviceEstablishes a connection,uses the connection,and then releases the connection.When a connection is established,negotiation has to do with getting both sides to agree on some parameters or values to be used during the communication.In the most cases the

29、 bits arrive to receiver in the order they were sentMessage sequences vs.byte streams1.4.3 Connection-Oriented vs.Connectionless(3)In connectionless serviceStore-and-forward switching vs.cut-through switchingIt is possible that the messages arrive to receiver out of order they were sent.Unreliable c

30、onnectionless service is called datagramReliable service vs.unreliable service Must have acknowledgement or need not one1.4.4 Service Primitives(1)A service is provided to the layer above as primitivesHypothetical example of service primitives that may provide a reliable byte stream(connection-orien

31、ted)service1.4.4 Service Primitives(2)Hypothetical example of how these primitives may be used for a client-server interactionClientServerLISTEN(0)ACCEPT RECEIVESEND(4)DISCONNECT(6)CONNECT(1)SENDRECEIVEDISCONNECT(5)Connect requestAccept responseRequest for dataReplyDisconnectDisconnect(2)(3)1.4.5 Re

32、lationship of Services to ProtocolsA layer provides a service to the one above verticalA layer talks to its peer using a protocol horizontalProblems:15,181.5 Reference ModelsThe OSI Reference ModelThe TCP/IP Reference ModelModel used for this CourseCritique of OSI and TCP/IP1.5.1 The OSI Reference M

33、odelA principled,international standard,seven layer model to connect different systemsProvides functions needed by usersConverts different representationsManages task dialogsProvides end-to-end deliverySends packets over multiple linksSends frames of informationSends bits as signals1.5.2 The TCP/IP

34、Reference ModelA four layer model derived from experimentation;omits some OSI layers and uses the IP as the network layer.IP is the“narrow waist”of the InternetProtocols are shown in their respective layers1.5.3 Model used for this CourseIt is based on the TCP/IP model but we call out the physical l

35、ayer and look beyond Internet protocols.1.5.4 Critique of OSI&TCP/IPOSI+Very influential model with clear conceptsModels,protocols and adoption all bogged down by politics and complexityTCP/IP+Very successful protocols that worked well and thrivedWeak model derived after the fact from protocols1.6 E

36、xample NetworksThe Internet3G mobile phone networksWireless LANsRFID and sensor networks1.6.1 Internet(1)Overview of the Internet architecture1.6.1 Internet(2)Access network is the physical links that connect an end system to the edge routerThe technology includesADSLEthernetFTTHWiFiWiMAXMobile comm

37、unicationFrom KUROSE&ROSS,Computer Networking:A Top-Down Approach,5th Edition1.6.1 Internet(3)The modern Internet is more complex(1)ISP networks serve as the Internet backboneISPs connect or peer to exchange traffic at IXPsWithin each network routers switch packetsBetween networks,traffic exchange i

38、s set by business agreements1.6.1 Internet(4)The modern Internet is more complex(2)Customers connect at the edge by many meansCable,DSL,Fiber-to-the-Home,3G/4G wireless,dialupData centers concentrate many servers(“the cloud”)Most traffic is content from data centers(esp.video)The architecture contin

39、ues to evolve1.6.1 Internet(5)ICANN(The Internet Corporation for Assigned Names and Numbers)announced Available Pool of unallocated IPv4 Internet Addresses Now Completely Emptied in Feb.3,2011US,EU(European Union),and Japan have scheduled for IPv4 to convert into IPv61.6.1 Internet(6)Source:邬贺铨,中国下一

40、代互联网的研究和CNGI项目1.6.1 Internet(7)Chinas Next Generation Internet(CNGI)Source:邬贺铨,中国下一代互联网的研究和CNGI项目1.6.2 3G mobile phone networks(1)3G network is based on spatial cells;each cell provides wireless service to mobiles within it via a base station1.6.2 3G mobile phone networks(2)Base stations connect to

41、the core network to find other mobiles and send data to the phone network and InternetArchitecture of UMTS 3G network1.6.2 3G mobile phone networks(3)As mobiles move,base stations hand them off from one cell to the next,and the network tracks their locationSoft handover vs.hard handoverHandover1.6.2

42、 3G mobile phone networks(4)SecuritySIM(Subscriber Identity Module)cardAuthenticationCryptographic keys on the chip are used to encrypt transmissionsEncryption cell phone4G and WiMAX1.6.3 Wireless LANs(1)Two different communication modes in 802.11Infrastructure wireless LAN:Clients communicate via a

43、n AP(Access Point)that is wired to the rest of the network.Ad hoc networks:clients can communicate directly in same radio rang.1.6.3 Wireless LANs(2)Signals in the 2.4GHz ISM band vary in strength due to many effects,such as multipath fading due to reflectionsrequires complex transmission schemes,e.

44、g.,OFDM1.6.3 Wireless LANs(3)Radio broadcasts interfere with each other,and radio ranges may incompletely overlapCSMA(Carrier Sense Multiple Access)designs are used1.6.3 Wireless LANs(4)MobilityOver a single 802.11 networkAcross different networks(IEEE 802.21)Security(802.11i)WEP(Wireless Equivalent

45、 Privacy)was flawed and brokenWPA2(WiFi Protected Access)WAPI(Wireless Authentication Privacy Infrastructure):China standard(GB 15629)1.6.4 RFID&Sensor Networks(1)Passive UHF RFID networks everyday objectsTags(stickers with not even a battery)are placed(or embedded)on objectsBackscatter:readers send

46、 signals that the tags reflect to communicate1.6.4 RFID&Sensor Networks(2)The Category of RFID TagsPassive RFID tags have neither an electric plug nor a battery.Active RFID has a power source in the tag.The Category Frequency of RFIDUHF RFID(Ultra-High Frequency RFID)tags communicate at distance of

47、several meters.It is used on shipping pallets and some drivers licenses.HF RFID(High Frequency RFID)is likely to be in the passports,credit cards,books,and noncontact payment systems.LF RFID(low Frequency RFID)is used for animal tracking.1.6.4 RFID&Sensor Networks(3)The Problems in Using RFIDMultipl

48、e tags in reading rageLike 802.11:wait for a short random intervalSecurityMalwareVirus1.6.4 RFID&sensor networks(4)Sensor networks spread small devices over an areaMultihop network:devices send sensed data to collector via wireless hopsProblems:24,251.6.4 RFID&sensor networks(4)Sensor networks sprea

49、d small devices over an area(2)The connections can be wired or wireless(Wireless)Mesh networkThe full mesh topology The partial mesh topology using self-healing algorithms The figures from Wikipedia1.7 Network StandardizationStandards define what is needed for interoperabilitySome of the many standa

50、rds bodiesBodyAreaExamplesITUTelecommunicationsG.992,ADSLH.264,MPEG4IEEECommunications802.3,Ethernet802.11,WiFiIETFInternetRFC 2616,HTTP/1.1RFC 1034/1035,DNSW3CWebHTML5 standardCSS standardDiscussing Topics(1-1)1.Problem 262.To know the organization of IEEE,ACM,and their related works.Write Short re