Computer Networking Chapter 1

Introduction1-1Chapter 1IntroductionComputer Networking: A Top Down Approach ,4thedition. Jim Kurose, Keith RossAddison-Wesley, July 2007. 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 lotof 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 1996-2007J.F Kurose and K.W. Ross, All Rights ReservedIntroduction1-2Chapter 1: IntroductionOur goal:get “feel” and terminologymore depth, detail laterin courseapproach:use Internet as exampleOverview:what’s the Internet?what’s a protocol?network edge; hosts, access net, physical medianetwork core: packet/circuit switching, Internet structureperformance: loss, delay, throughputsecurityprotocol layers, service modelshistoryIntroduction1-3Chapter 1: roadmap1.1 What isthe Internet?1.2Network edgeend systems, access networks, links1.3Network corecircuit switching, packet switching, network structure1.4Delay, loss and throughput in packet-switched networks1.5Protocol layers, service models1.6Networks under attack: security1.7HistoryIntroduction1-4What’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)Introduction1-5“Cool” internet appliancesWorld’s smallest web serverhttp://www-ccs.cs.umass.edu/~shri/iPic.htmlIP picture framehttp://www.ceiva.com/Web-enabled toaster +weather forecasterInternet phonesIntroduction1-6What’s the Internet: “nuts and bolts” viewprotocolscontrol 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 ISPIntroduction1-7What’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 deliveryIntroduction1-8What’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, receiptIntroduction1-9What’s a protocol?a human protocol and a computer network protocol:Q:Other human protocols? HiHiGot thetime?2:00TCP connectionrequestTCP connectionresponseGet http://www.awl.com/kurose-rosstimeIntroduction1-10Chapter 1: roadmap1.1 What isthe Internet?1.2 Network edgeend systems, access networks, links1.3 Network corecircuit switching, packet switching, network structure1.4Delay, loss and throughput in packet-switched networks1.5Protocol layers, service models1.6Networks under attack: security1.7HistoryIntroduction1-11A closer look at network structure:network edge:applications and hostsaccess networks, physical media:wired, wireless communication linksnetwork core:interconnected routersnetwork of networksIntroduction1-12The 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, BitTorrenthIntroduction1-13Network edge: reliable data transfer serviceGoal:data transfer between end systemshandshaking:setup (prepare for) data transfer ahead of timeHello, hello back human protocolset up “state”in two communicating hostsTCP -Transmission Control Protocol Internet’s reliable data transfer serviceTCP service[RFC 793]reliable, in-orderbyte-stream data transferloss: acknowledgements and retransmissionsflow control:sender won’t overwhelm receivercongestion control:senders “slow down sending rate” when network congestedIntroduction1-14Network edge: best effort (unreliable) data transfer serviceGoal:data transfer between end systemssame as before!UDP-User Datagram Protocol [RFC 768]: connectionless unreliable data transferno flow controlno congestion controlApp’s using TCP:HTTP (Web), FTP (file transfer), Telnet (remote login), SMTP (email)App’s using UDP:streaming media, teleconferencing, DNS, Internet telephonyIntroduction1-15Access 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?Introduction1-16Residential access: point to point accessDialup via modemup to 56Kbps direct access to router (often less)Can’t surf and phone at same time: can’t be “always on”DSL:digital subscriber linedeployment: telephone company (typically)up to 1 Mbps upstream (today typically < 256 kbps)up to 8 Mbps downstream (today typically < 1 Mbps)dedicated physical line to telephone central officeIntroduction1-17Residential access: cable modemsHFC: hybrid fiber coaxasymmetric: up to 30Mbps downstream, 2 Mbps upstreamnetworkof cable and fiber attaches homes to ISP routerhomes share access to router deployment: available via cable TV companiesIntroduction1-18Residential access: cable modemsDiagram: http://www.cabledatacomnews.com/cmic/diagram.htmlIntroduction1-19Cable Network Architecture: Overviewhomecable headendcable distributionnetwork (simplified)Typically 500 to 5,000 homesIntroduction1-20Cable Network Architecture: Overviewhomecable headendcable distributionnetworkserver(s)Introduction1-21Cable Network Architecture: Overviewhomecable headendcable distributionnetwork (simplified)Introduction1-22Cable Network Architecture: Overviewhomecable headendcable distributionnetworkChannelsVIDEOVIDEOVIDEOVIDEOVIDEOVIDEODATADATACONTROL123456789FDM (more shortly):Introduction1-23Company access: local area networkscompany/univ local area network(LAN) connects end system to edge routerEthernet:10 Mbs, 100Mbps, 1Gbps, 10Gbps Ethernetmodern configuration: end systems connect into EthernetswitchLANs: chapter 5Introduction1-24Wireless access networksshared wirelessaccess 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 areabasestationmobilehostsrouterIntroduction1-25Home networksTypical home network components: DSL or cable modemrouter/firewall/NATEthernetwireless accesspointwirelessaccess pointwirelesslaptopsrouter/firewallcablemodemto/fromcableheadendEthernetIntroduction1-26Physical MediaBit: propagates betweentransmitter/rcvr pairsphysical link:what lies between transmitter & receiverguided media:signals propagate in solid media: copper, fiber, coaxunguided media:signals propagate freely, e.g., radioTwisted Pair (TP)two insulated copper wiresCategory 3: traditional phone wires, 10 Mbps EthernetCategory 5: 100Mbps EthernetIntroduction1-27Physical Media: coax, fiberCoaxial cable:two concentric copper conductorsbidirectionalbaseband:single channel on cablelegacy Ethernetbroadband:multiple channels on cableHFCFiber optic cable:glass fiber carrying light pulses, each pulse a bithigh-speed operation:high-speed point-to-point transmission (e.g., 10’s-100’s Gps)low error rate: repeaters spaced far apart ; immune to electromagnetic noiseIntroduction1-28Physical media: radiosignal carried in electromagnetic spectrumno physical “wire”bidirectionalpropagation environment effects:reflection obstruction by objectsinterferenceRadio link types:terrestrial microwavee.g. up to 45 Mbps channelsLAN(e.g., Wifi)11Mbps, 54 Mbpswide-area(e.g., cellular)3G cellular: ~ 1 MbpssatelliteKbps to 45Mbps channel (or multiple smaller channels)270 msec end-end delaygeosynchronous versus low altitudeIntroduction1-29Chapter 1: roadmap1.1 What isthe Internet?1.2Network edgeend systems, access networks, links1.3 Network corecircuit switching, packet switching, network structure1.4Delay, loss and throughput in packet-switched networks1.5Protocol layers, service models1.6Networks under attack: security1.7HistoryIntroduction1-30The Network Coremesh of interconnected routersthefundamental question:how is data transferred through net?circuit switching:dedicated circuit per call: telephone netpacket-switching:data sent thru net in discrete “chunks”Introduction1-31Network Core: Circuit SwitchingEnd-end resources reserved for “call”link bandwidth, switch capacitydedicated resources: no sharingcircuit-like (guaranteed) performancecall setup requiredIntroduction1-32Network Core: Circuit Switchingnetwork resources (e.g., bandwidth) divided into “pieces”pieces allocated to callsresource piece idleif not used by owning call (no sharing)dividing link bandwidth into “pieces”frequency divisiontime divisionIntroduction1-33Circuit Switching: FDM and TDMFDMfrequencytimeTDMfrequencytime4 usersExample:Introduction1-34Numerical exampleHow long does it take to send a file of 640,000 bits from host A to host B over a circuit-switched network?All links are 1.536 MbpsEach link uses TDM with 24 slots/sec500 msec to establish end-to-end circuitLet’s work it out!Introduction1-35Network Core: Packet Switchingeach end-end data stream divided into packetsuser A, B packets sharenetwork resourceseach packet uses full link bandwidth resources used as neededresource contention:aggregate resource demand can exceed amount availablecongestion: packets queue, wait for link usestore and forward: packets move one hop at a timeNode receives complete packet before forwardingBandwidth division into “pieces”Dedicated allocationResource reservationIntroduction1-36Packet Switching: Statistical MultiplexingSequence of A & B packets does not have fixed pattern, bandwidth shared on demand statistical multiplexing.TDM: each host gets same slot in revolving TDM frame.ABC100 Mb/sEthernet1.5 Mb/sDEstatistical multiplexingqueue of packetswaiting for outputlinkIntroduction1-37Packet-switching: store-and-forwardtakes L/R seconds to transmit (push out) packet of L bits on to link at R bpsstore and forward: entire packet must arrive at router before it can be transmitted on next linkdelay = 3L/R (assuming zero propagation delay)Example:L = 7.5 MbitsR = 1.5 Mbpstransmission delay = 15 secRRRLmore on delay shortly …Introduction1-38Packet switching versus circuit switching1 Mb/s linkeach user: 100 kb/s when “active”active 10% of timecircuit-switching:10 userspacket switching:with 35 users, probability > 10 active at same time is less than .0004Packet switching allows more users to use network!N users1 Mbps linkQ: how did we get value 0.0004?Introduction1-39Packet switching versus circuit switchinggreat for bursty dataresource sharingsimpler, no call setupexcessive congestion:packet delay and lossprotocols needed for reliable data transfer, congestion controlQ: How to provide circuit-like behavior?bandwidth guarantees needed for audio/video appsstill an unsolved problem (chapter 7)Is packet switching a “slam dunk winner?”Q: human analogies of reserved resources (circuit switching) versus on-demand allocation (packet-switching)?Introduction1-40Internet structure: network of networksroughly hierarchicalat center: “tier-1” ISPs (e.g., Verizon, Sprint, AT&T, Cable and Wireless), national/international coveragetreat each other as equalsTier 1 ISPTier 1 ISPTier 1 ISPTier-1 providers interconnect (peer) privatelyIntroduction1-41Tier-1 ISP: e.g., Sprint…to/from customerspeeringto/from backbone….………POP: point-of-presenceIntroduction1-42Internet structure: network of networks“Tier-2” ISPs: smaller (often regional) ISPsConnect to one or more tier-1 ISPs, possibly other tier-2 ISPsTier 1 ISPTier 1 ISPTier 1 ISPTier-2 ISPTier-2 ISPTier-2 ISPTier-2 ISPTier-2 ISPTier-2 ISP pays tier-1 ISP for connectivity to rest of Internettier-2 ISP is customeroftier-1 providerTier-2 ISPs also peer privately with each other.Introduction1-43Internet structure: network of networks“Tier-3” ISPs and local ISPs last hop (“access”) network (closest to end systems)Tier 1 ISPTier 1 ISPTier 1 ISPTier-2 ISPTier-2 ISPTier-2 ISPTier-2 ISPTier-2 ISPlocalISPlocalISPlocalISPlocalISPlocalISPTier 3ISPlocalISPlocalISPlocalISPLocal and tier-3 ISPs are customersofhigher tier ISPsconnecting them to rest of InternetIntroduction1-44Internet structure: network of networksa packet passes through many networks!Tier 1 ISPTier 1 ISPTier 1 ISPTier-2 ISPTier-2 ISPTier-2 ISPTier-2 ISPTier-2 ISPlocalISPlocalISPlocalISPlocalISPlocalISPTier 3ISPlocalISPlocalISPlocalISPIntroduction1-45Chapter 1: roadmap1.1 What isthe Internet?1.2Network edgeend systems, access networks, links1.3Network corecircuit switching, packet switching, network structure1.4 Delay, loss and throughput in packet-switched networks1.5Protocol layers, service models1.6Networks under attack: security1.7HistoryIntroduction1-46How do loss and delay occur?packets queuein router bufferspacket arrival rate to link exceeds output link capacitypackets queue, wait for turnABpacket being transmitted (delay)packets queueing(delay)free (available) buffers: arriving packets dropped (loss) if no free buffersIntroduction1-47Four sources of packet delay1. nodal processing:check bit errorsdetermine output linkABpropagationtransmissionnodalprocessingqueueing2. queueingtime waiting at output link for transmission depends on congestion level of routerIntroduction1-48Delay in packet-switched networks3. Transmission delay:R=link bandwidth (bps)L=packet length (bits)time to send bits into link = L/R4. Propagation delay:d = length of physical links = propagation speed in medium (~2x108m/sec)propagation delay = d/sABpropagationtransmissionnodalprocessingqueueingNote: s and R are very different quantities!Introduction1-49Caravan analogycars “propagate” at 100 km/hrtoll booth takes 12 sec to service car (transmission time)car~bit; caravan ~ packetQ: How long until caravan is lined up before 2nd toll booth?Time to “push” entire caravan through toll booth onto highway = 12*10 = 120 secTime for last car to propagate from 1st to 2nd toll both: 100km/(100km/hr)= 1 hrA: 62 minutestoll boothtoll boothten-car caravan100 km100 kmIntroduction1-50Caravan analogy (more)Cars now “propagate” at 1000 km/hrToll booth now takes 1 min to service a carQ:Will cars arrive to 2nd booth before all cars serviced at 1st booth?Yes!After 7 min, 1st car at 2nd booth and 3 cars still at 1st booth.1st bit of packet can arrive at 2nd router before packet is fully transmitted at 1st router!See Ethernet applet at AWL Web sitetoll boothtoll boothten-car caravan100 km100 kmIntroduction1-51Nodal delaydproc= processing delaytypically a few microsecs or lessdqueue= queuing delaydepends on congestiondtrans= transmission delay= L/R, significant for low-speed linksdprop= propagation delaya few microsecs to hundreds of msecsproptransqueueprocnodaldddddIntroduction1-52Queueing delay (revisited)R=link bandwidth (bps)L=packet length (bits)a=average packet arrival ratetraffic intensity = La/RLa/R ~ 0: average queueing delay smallLa/R -> 1: delays become largeLa/R > 1: more “work” arriving than can be serviced, average delay infinite!Introduction1-53“Real” Internet delays and routesWhat do “real” Internet delay & loss look like? Tracerouteprogram:provides delay measurement from source to router along end-end Internet path towards destination. For all i:sends three packets that will reach router ion path towards destinationrouter iwill return packets to sendersender times interval between transmission and reply.3 probes3 probes3 probesIntroduction1-54“Real” Internet delays and routes1 cs-gw (128.119.240.254) 1 ms 1 ms 2 ms2 border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145) 1 ms 1 ms 2 ms3 cht-vbns.gw.umass.edu (128.119.3.130) 6 ms 5 ms 5 ms4 jn1-at1-0-0-19.wor.vbns.net (204.147.132.129) 16 ms 11 ms 13 ms 5 jn1-so7-0-0-0.wae.vbns.net (204.147.136.136) 21 ms 18 ms 18 ms 6 abilene-vbns.abilene.ucaid.edu (198.32.11.9) 22 ms 18 ms 22 ms7 nycm-wash.abilene.ucaid.edu (198.32.8.46) 22 ms 22 ms 22 ms8 62.40.103.253 (62.40.103.253) 104 ms 109 ms 106 ms9 de2-1.de1.de.geant.net (62.40.96.129) 109 ms 102 ms 104 ms10 de.fr1.fr.geant.net (62.40.96.50) 113 ms 121 ms 114 ms11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms12 nio-n2.cssi.renater.fr (193.51.206.13) 111 ms 114 ms 116 ms13 nice.cssi.renater.fr (195.220.98.102) 123 ms 125 ms 124 ms14 r3t2-nice.cssi.renater.fr (195.220.98.110) 126 ms 126 ms 124 ms15 eurecom-valbonne.r3t2.ft.net (193.48.50.54) 135 ms 128 ms 133 ms16 194.214.211.25 (194.214.211.25) 126 ms 128 ms 126 ms17 * * *18 * * *19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136mstraceroute:gaia.cs.umass.edu to www.eurecom.frThree delay measurements from gaia.cs.umass.edu to cs-gw.cs.umass.edu * means no response (probe lost, router not replying)trans-oceaniclinkIntroduction1-55Packet lossqueue (aka buffer) preceding link in buffer has finite capacitypacket arriving to full queue dropped (aka lost)lost packet may be retransmitted by previous node, by source end system, or not at allABpacket being transmittedpacket arriving tofull bufferis lostbuffer (waiting area)Introduction1-56Throughputthroughput:rate (bits/time unit) at which bits transferred between sender/receiverinstantaneous:rate at given point in timeaverage:rate over long(er) period of timeserver, withfile of F bits to send to clientlink capacityRsbits/seclink capacityRcbits/secpipe that can carryfluid at rateRsbits/sec)pipe that can carryfluid at rateRcbits/sec)server sends bits (fluid) into pipeIntroduction1-57Throughput (more)Rs< RcWhat is average end-end throughput?Rsbits/secRcbits/secRs> RcWhat is average end-end throughput?Rsbits/secRcbits/seclink on end-end path that constrains end-end throughputbottleneck linkIntroduction1-58Throughput: Internet scenario10 connections (fairly) share backbone bottleneck link Rbits/secRsRsRsRcRcRcRper-connection end-end throughput: min(Rc,Rs,R/10)in practice: Rcor Rsis often bottleneckIntroduction1-59Chapter 1: roadmap1.1 What isthe Internet?1.2Network edgeend systems, access networks, links1.3Network corecircuit switching, packet switching, network structure1.4Delay, loss and throughput in packet-switched networks1.5 Protocol layers, service models1.6Networks under attack: security1.7HistoryIntroduction1-60Protocol “Layers”Networks are complex! many “pieces”:hostsrouterslinks of various mediaapplicationsprotocolshardware, softwareQuestion:Is there any hope of organizingstructure of network?Or at least our discussion of networks?Introduction1-61Organization of air travela series of stepsticket (purchase)baggage (check)gates (load)runway takeoffairplane routingticket (complain)baggage (claim)gates (unload)runway landingairplane routingairplane routingIntroduction1-62ticket (purchase)baggage (check)gates (load)runway (takeoff)airplane routingdepartureairportarrivalairportintermediate air-trafficcontrol centersairplane routingairplane routingticket (complain)baggage (claimgates (unload)runway (land)airplane routingticketbaggagegatetakeoff/landingairplane routingLayering of airline functionalityLayers: each layer implements a servicevia its own internal-layer actionsrelying on services provided by layer belowIntroduction1-63Why layering?Dealing with complex systems:explicit structure allows identification, relationship of complex system’s pieceslayered reference modelfor discussionmodularization eases maintenance, updating of systemchange of implementation of layer’s service transparent to rest of systeme.g., change in gate procedure doesn’t affect rest of systemlayering considered harmful?Introduction1-64Internet protocol stackapplication:supporting network applicationsFTP, SMTP, HTTPtransport:process-process data transferTCP, UDPnetwork:routing of datagrams from source to destinationIP, routing protocolslink:data transfer between neighboring network elementsPPP, Ethernetphysical:bits “on the wire”applicationtransportnetworklinkphysicalIntroduction1-65ISO/OSI reference modelpresentation:allow applications to interpret meaning of data, e.g., encryption, compression, machine-specific conventionssession:synchronization, checkpointing, recovery of data exchangeInternet stack “missing” these layers!these services, if needed,must be implemented in applicationneeded?applicationpresentationsessiontransportnetworklinkphysicalIntroduction1-66sourceapplicationtransportnetworklinkphysicalHtHnMsegmentHtdatagramdestinationapplicationtransportnetworklinkphysicalHtHnHlMHtHnMHtMMnetworklinkphysicallinkphysicalHtHnHlMHtHnMHtHnMHtHnHlMrouterswitchEncapsulationmessageMHtMHnframeIntroduction1-67Chapter 1: roadmap1.1 What isthe Internet?1.2Network edgeend systems, access networks, links1.3Network corecircuit switching, packet switching, network structure1.4 Delay, loss and throughput in packet-switched networks1.5Protocol layers, service models1.6 Networks under attack: security1.7HistoryIntroduction1-68Network Securityattacks on Internet infrastructure:infecting/attacking hosts: malware, spyware, worms, unauthorized access (data stealing, user accounts)denial of service: deny access to resources (servers, link bandwidth) Internet not originally designed with (much) security in mindoriginal vision:“a group of mutually trusting users attached to a transparent network” Internet protocol designers playing “catch-up”Security considerations in all layers!Introduction1-69What can bad guys do: malware?Spyware:infection by downloading web page with spywarerecords keystrokes, web sites visited, upload info to collection siteVirusinfection by receiving object (e.g., e-mail attachment), actively executingself-replicating: propagate itself to other hosts, usersWorm:infection by passively receiving object that gets itself executedself-replicating: propagates to other hosts, usersSapphire Worm: aggregate scans/secin first 5 minutes of outbreak (CAIDA, UWisc data)Introduction1-70Denial of service attacksattackers make resources (server, bandwidth) unavailable to legitimate traffic by overwhelming resource with bogus traffic1.select target2.break into hosts around the network (see malware)3.send packets toward target from compromised hoststargetIntroduction1-71Sniff, modify, delete your packetsPacket sniffing: broadcast media (shared Ethernet, wireless)promiscuous network interface reads/records all packets (e.g., including passwords!) passing byABCsrc:B dest:A payloadEthereal software used for end-of-chapter labs is a (free) packet-sniffermore on modification, deletion laterIntroduction1-72Masquerade as youIP spoofing: send packet with false source addressABCsrc:Bdest:A payloadIntroduction1-73Masquerade as youIP spoofing: send packet with false source addressrecord-and-playback: sniff sensitive info (e.g., password), and use laterpassword holder is that user from system point of viewABCsrc:B dest:A user: B; password: fooIntroduction1-74Masquerade as youIP spoofing: send packet with false source addressrecord-and-playback: sniff sensitive info (e.g., password), and use laterpassword holder is that user from system point of viewABlater …..Csrc:B dest:A user: B; password: fooIntroduction1-75Network Securitymore throughout this coursechapter 8: focus on securitycrypographic techniques: obvious uses and not so obvious usesIntroduction1-76Chapter 1: roadmap1.1 What isthe Internet?1.2Network edgeend systems, access networks, links1.3Network corecircuit switching, packet switching, network structure1.4Delay, loss and throughput in packet-switched networks1.5 Protocol layers, service models1.6Networks under attack: security1.7 HistoryIntroduction1-77Internet History1961:Kleinrock -queueing theory shows effectiveness of packet-switching1964:Baran -packet-switching in military nets1967:ARPAnet conceived by Advanced Research Projects Agency1969:first ARPAnet node operational1972:ARPAnet public demonstrationNCP (Network Control Protocol) first host-host protocol first e-mail programARPAnet has 15 nodes1961-1972: Early packet-switching principlesIntroduction1-78Internet History1970:ALOHAnet satellite network in Hawaii1974:Cerf and Kahn -architecture for interconnecting networks1976:Ethernet at Xerox PARCate70’s:proprietary architectures: DECnet, SNA, XNAlate 70’s:switching fixed length packets (ATM precursor)1979:ARPAnet has 200 nodesCerf and Kahn’s internetworking principles:minimalism, autonomy -no internal changes required to interconnect networksbest effort service modelstateless routersdecentralized controldefine today’s Internet architecture1972-1980: Internetworking, new and proprietary netsIntroduction1-79Internet History1983:deployment of TCP/IP1982:smtp e-mail protocol defined 1983:DNS defined for name-to-IP-address translation1985:ftp protocol defined1988:TCP congestion controlnew national networks: Csnet, BITnet, NSFnet, Minitel100,000 hosts connected to confederation of networks1980-1990: new protocols, a proliferation of networksIntroduction1-80Internet HistoryEarly 1990’s: ARPAnet decommissioned1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995)early 1990s:Webhypertext [Bush 1945, Nelson 1960’s]HTML, HTTP: Berners-Lee1994: Mosaic, later Netscapelate 1990’s: commercializationof the WebLate 1990’s –2000’s:more killer apps: instant messaging, P2P file sharingnetwork security to forefrontest. 50 million host, 100 million+ usersbackbone links running at Gbps1990, 2000’s: commercialization, the Web, new appsIntroduction1-81Internet History2007:~500 million hostsVoice, Video over IPP2P applications: BitTorrent (file sharing) Skype (VoIP), PPLive (video)more applications: YouTube, gamingwireless, mobilityIntroduction1-82Introduction: SummaryCovered a “ton” of material!Internet overviewwhat’s a protocol?network edge, core, access networkpacket-switching versus circuit-switchingInternet structureperformance: loss, delay, throughputlayering, service modelssecurityhistoryYou now have:context, overview, “feel” of networkingmore depth, detail to follow!

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