Slide 1What’s the Internet: “nuts and bolts” viewSlide 3What’s the Internet: a service viewA closer look at network structure:The network edge:Access networks and physical mediaDial-up ModemDigital Subscriber Line (DSL)Residential access: cable modemsCable Network Architecture: OverviewSlide 12Slide 13Fiber to the HomeEthernet Internet accessWireless access networksPhysical MediaPhysical Media: coax, fiberPhysical media: radioThe Network CoreNetwork Core: Circuit SwitchingSlide 22Circuit Switching: FDM and TDMNumerical exampleNetwork Core: Packet SwitchingPacket Switching: Statistical MultiplexingPacket-switching: store-and-forwardPacket switching versus circuit switchingSlide 29Internet structure: network of networksTier-1 ISP: e.g., SprintSlide 32Slide 33Slide 34How do loss and delay occur?Four sources of packet delayDelay in packet-switched networksNodal delayQueueing delay (revisited)“Real” Internet delays and routesSlide 41Packet lossThroughputThroughput (more)Throughput: Internet scenarioWhy layering?Internet protocol stackISO/OSI reference modelEncapsulationIntroduction 1-1Chapter 1IntroductionComputer Networking: A Top Down Approach ,5th edition. 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 1996-2009J.F Kurose and K.W. Ross, All Rights ReservedIntroduction 1-2What’s the Internet: “nuts and bolts” viewmillions of connected computing devices: hosts = end systems  running network appsHome networkInstitutional networkMobile networkGlobal ISPRegional ISProuterPCserverwirelesslaptopcellular handheldwiredlinksaccess pointscommunication linksfiber, copper, radio, satellitetransmission rate = bandwidthrouters: forward packets (chunks of data)Introduction 1-3What’s the Internet: “nuts and bolts” viewprotocols control sending, receiving of msgse.g., TCP, IP, HTTP, Skype, EthernetInternet: “network of networks”loosely hierarchicalpublic Internet versus private intranetInternet standardsRFC: Request for commentsIETF: Internet Engineering Task ForceHome networkInstitutional networkMobile networkGlobal ISPRegional ISPIntroduction 1-4What’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 1-5A closer look at network structure:network edge: applications and hostsaccess networks, physical media: wired, wireless communication links network core: interconnected routersnetwork of networksIntroduction 1-6The 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 1-7Access networks and physical mediaQ: 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?telephonenetworkInternethomedial-upmodemISPmodem(e.g., AOL)homePCcentral officeUses existing telephony infrastructureHome is connected to central officeup to 56Kbps direct access to router (often less)Can’t surf and phone at same time: not “always on”Dial-up ModemtelephonenetworkDSLmodemhomePChomephoneInternetDSLAMExisting phone line:0-4KHz phone; 4-50KHz upstream data; 50KHz-1MHz downstream datasplittercentralofficeDigital Subscriber Line (DSL)Also uses existing telephone infrastruture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 1-10Residential access: cable modemsDoes not use telephone infrastructureInstead uses cable TV infrastructureHFC: hybrid fiber coaxasymmetric: up to 30Mbps downstream, 2 Mbps upstreamnetwork of cable and fiber attaches homes to ISP routerhomes share access to router unlike DSL, which has dedicated accessIntroduction 1-11Cable Network Architecture: Overviewhomecable headendcable distributionnetwork (simplified)Typically 500 to 5,000 homesIntroduction 1-12Cable Network Architecture: Overviewhomecable headendcable distributionnetwork (simplified)Introduction 1-13Cable Network Architecture: Overviewhomecable headendcable distributionnetworkChannelsVIDEOVIDEOVIDEOVIDEOVIDEOVIDEODATADATACONTROL1 2 3 45 6 7 8 9FDM (more shortly):ONTOLTcentral officeopticalsplitterONTONTopticalfiberopticalfibersInternetFiber to the HomeOptical links from central office to the homeTwo competing optical technologies: Passive Optical network (PON) Active Optical Network (A0N)Much higher Internet rates; fiber also carries television and phone servicesONT  optical network terminatorOLT  optical line terminator100 Mbps100 Mbps100 Mbps1 GbpsserverEthernetswitchInstitutionalrouterTo Institution’sISPEthernet Internet accessTypically used in companies, universities, etc10 Mbs, 100Mbps, 1Gbps, 10Gbps EthernetToday, end systems typically connect into Ethernet switchIntroduction 1-16Wireless access networksshared wireless access network connects end system to routervia base station aka “access point”wireless LANs:802.11b/g (WiFi): 11 or 54 Mbpswider-area wireless accessprovided by telco operator~1Mbps over cellular system (EVDO, HSDPA)next up (?): WiMAX (10’s Mbps) over wide