Chapter 1IntroductionComputer Networking: A Top Down Approach ,5thedition. Jim Kurose, Keith RossAddison-Wesley, April 2009.A note on the use of these ppt slides:We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following: If you use these slides (e.g., in a class) in substantially unaltered form, that you mention their source (after all, we’d like people to use our book!) If you post any slides in substantially unaltered form on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material.Thanks and enjoy! JFK/KWRAll material copyright 1996-2010J.F Kurose and K.W. Ross, All Rights ReservedIntroduction 1-1What’s the Internet: “nuts and bolts” view millions of connected computing devices: hosts = end systems running network appsHome networkInstitutional networkMobile networkGlobal ISPRegional ISProuterPCserverwirelesslaptopcellular handheldwiredlinksaccess pointscommunication links fiber, copper, radio, satellite transmission rate = bandwidthrouters:forward packets (chunks of data)Introduction 1-2What’s the Internet: “nuts and bolts” viewprotocolscontrol sending, receiving of msgs e.g., TCP, IP, HTTP, Skype, EthernetInternet: “network of networks” loosely hierarchical public Internet versus private intranet Internet standards RFC: Request for comments Documents containing internet standards IETF: Internet Engineering Task Force Develops internet standardsHome networkInstitutional networkMobile networkGlobal ISPRegional ISPIntroduction 1-3What’s a protocol?human protocols: “what’s the time?” “I have a question” introductions… specific msgs sent… specific actions taken when msgs received, or other eventsnetwork protocols: machines rather than humans all communication activity in Internet governed by protocolsprotocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receiptIntroduction 1-4What’s a protocol?a human protocol and a computer network protocol:Q: Other human protocols? HiHiGot thetime?2:00TCP connectionresponseGet http://www.awl.com/kurose-ross<file>timeIntroduction 1-5TCP connectionrequestWhat’s the Internet: a service view communication infrastructure enables distributed applications: Web, VoIP, email, games, e-commerce, file sharing communication services provided to apps: reliable data delivery from source to destination “best effort” (unreliable) data deliveryIntroduction 1-6Chapter 1: roadmap1.1 What isthe Internet?1.2 Network edge end systems, access networks, links1.3 Network core circuit switching, packet switching, network structure1.4 Delay, loss and throughput in packet-switched networks1.5 Protocol layers, service models1.6 Networks under attack: security1.7 HistoryIntroduction 1-7“Fun” internet appliancesIP picture framehttp://www.ceiva.com/Web-enabled toaster +weather forecasterInternet phonesInternet refrigeratorSlingbox: watch,control cable TV remotelyIntroduction 1-8A closer look at network structure: network edge:hosts=end systems access networks, physical media that connect an end system to the first router (known as the edge router): wired, wireless communication links network core: interconnected routers network of networksIntroduction 1-9The network edge: end systems (hosts): run application programs e.g. Web, email at “edge of network”client/serverpeer-peer client/server model client host requests, receives service from always-on server e.g. Web browser/server; email client/server peer-peer model: minimal (or no) use of dedicated servers e.g. Skype, BitTorrentIntroduction 1-10Access networks: Physical Links that Connect an End System to the First RouterQ: How to connect end systems to edge router? residential access nets institutional access networks (school, company) mobile access networksKeep in mind: bandwidth (bits per second) of access network? shared or dedicated?Introduction 1-11telephonenetworkInternethomedial-upmodemISPmodem(e.g., AOL)homePCcentral office 10% of residential users in US used dial-up in 2008 uses existing telephony infrastructure home directly-connected to central office Disadvantages Slow: up to 56Kbps direct access to router (often less) can’t surf, phone at same time: not “always on”Dial-up ModemIntroduction 1-12telephonenetworkDSLmodemhomePChomephoneInternetDSLAMExisting phone line:0-4KHz phone; 4-50KHz upstream data; 50KHz-1MHz downstream datasplittercentralofficeDigital Subscriber Line (DSL) uses existing telephone infrastructure up to 1 Mbps upstream (today typically < 256 kbps) up to 8 Mbps downstream (today typically < 1 Mbps) dedicated physical line to telephone central officeIntroduction 1-13DSL ContinuedIntroduction1-14 Transmission rate available to a residence is a function of The distance between the home and the CO Residence must be within 5 to 10 miles of the CO Gauge of the twisted pair line Degree of electrical interferenceResidential access: cable modems uses cable TV infrastructure, rather than telephone infrastructure HFC: hybrid fiber coax asymmetric: up to 30Mbps downstream, 2 Mbps upstream network of cable, fiber attaches homes to ISP router homes share access to router unlike DSL, which has dedicated accessIntroduction 1-15Head EndFiberNodeFiberNodeCoaxial cableFiber Optic Cablehomecable headendcable distributionnetwork (simplified)Typically 500 to 5,000 homesIntroduction 1-16Cable Network Architecture: Overviewhomecable headendcable distributionnetworkserver(s)Introduction 1-17Cable Network Architecture: OverviewCable Network Architecture: Overviewhomecable headendcable distributionnetwork (simplified)Introduction 1-18homecable headendcable distributionnetworkChannelsVIDEOVIDEOVIDEOVIDEOVIDEOVIDEODATADATACONTROL1 2 3 45 6 7 8 9FDM (more shortly):Introduction 1-19Cable Network Architecture: OverviewONTOLTcentral officeopticalsplitterONTONTopticalfiberopticalfibersInternetFiber to the Home Optical links from central office to the home Optical Line
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