is the Internet What is a protocol Network edge Network core Performance loss delay throughput Layering encapsulation service models Security History COMPSCI 453 Computer Networks ID: 1001116
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1. IntroductionOverview. What is the Internet? What is a protocol?Network edgeNetwork corePerformance: loss, delay, throughputLayering, encapsulation, service modelsSecurityHistoryCOMPSCI 453 Computer NetworksProfessor Jim KuroseCollege of Information and Computer SciencesUniversity of Massachusetts Class textbook: Computer Networking: A Top-Down Approach (8th ed.)J.F. Kurose, K.W. RossPearson, 2020http://gaia.cs.umass.edu/kurose_ross
2. Protocol “layers” and reference modelsNetworks are complex,with many “pieces”:hostsrouterslinks of various mediaapplicationsprotocolshardware, softwareQuestion: is there any hope of organizing structure of network?and/or our discussion of networks?
3. Example: organization of air travela series of steps, involving many servicesticket (purchase)baggage (check)gates (load)runway takeoffairplane routingticket (complain)baggage (claim)gates (unload)runway landingairplane routingairplane routing How would you define/discuss the system of airline travel?end-to-end transfer of person plus baggage
4. Example: organization of air travelticket (purchase)baggage (check)gates (load)runway takeoffairplane routingticket (complain)baggage (claim)gates (unload)runway landingairplane routingairplane routingticketing servicebaggage servicegate servicerunway servicerouting servicelayers: each layer implements a servicevia its own internal-layer actionsrelying on services provided by layer below
5. Why layering?Approach to designing/discussing complex systems:explicit structure allows identification, relationship of system’s pieceslayered reference model for discussionmodularization eases maintenance, updating of systemchange in layer's service implementation: transparent to rest of systeme.g., change in gate procedure doesn’t affect rest of system
6. Layered Internet protocol stackapplication: supporting network applicationsHTTP, IMAP, SMTP, DNStransport: process-process data transferTCP, UDPnetwork: routing of datagrams from source to destinationIP, routing protocolslink: data transfer between neighboring network elementsEthernet, 802.11 (WiFi), PPPphysical: bits “on the wire”linkapplicationnetworktransportphysicalapplicationtransportnetworklinkphysical
7. Services, Layering and Encapsulationsourcetransport-layer protocol encapsulates application-layer message, M, with transport layer-layer header Ht to create a transport-layer segmentHt used by transport layer protocol to implement its serviceapplicationtransportnetworklinkphysicaldestinationapplicationtransportnetworklinkphysicalTransport-layer protocol transfers M (e.g., reliably) from one process to another, using services of network layerHtMApplication exchanges messages to implement some application service using services of transport layerM
8. Services, Layering and EncapsulationsourceTransport-layer protocol transfers M (e.g., reliably) from one process to another, using services of network layerHtMnetwork-layer protocol encapsulates transport-layer segment [Ht | M] with network layer-layer header Hn to create a network-layer datagram Hn used by network layer protocol to implement its serviceapplicationtransportnetworklinkphysicaldestinationMapplicationtransportnetworklinkphysicalMHtHnNetwork-layer protocol transfers transport-layer segment [Ht | M] from one host to another, using link layer services
9. Services, Layering and EncapsulationsourceHtMlink-layer protocol encapsulates network datagram [Hn| [Ht |M], with link-layer header Hl to create a link-layer frame applicationtransportnetworklinkphysicaldestinationMapplicationtransportnetworklinkphysicalMHtHnLink-layer protocol transfers datagram [Hn| [Ht |M] from host to neighboring host, using network-layer servicesMHtHnHlMHtHnNetwork-layer protocol transfers transport-layer segment [Ht | M] from one host to another, using link layer services
10. Services, Layering and EncapsulationsourceapplicationtransportnetworklinkphysicaldestinationapplicationtransportnetworklinkphysicalHtMMMHtHn MHtHnHlMHtHnHtMM messagesegmentdatagramframeMHtHnHl
11. networklinkphysicalapplicationtransportnetworklinkphysicalapplicationtransportnetworklinkphysicalEncapsulation: an end-end viewsourceHtHnMsegmentHtdatagramdestinationHtHnHlMHtHnMHtMMHtHnHlMHtHnMHtHnMHtHnHlMrouterswitchmessageMHtMHnframelinkphysical
12. IntroductionCOMPSCI 453 Computer NetworksProfessor Jim KuroseCollege of Information and Computer SciencesUniversity of Massachusetts Class textbook: Computer Networking: A Top-Down Approach (8th ed.)J.F. Kurose, K.W. RossPearson, 2020http://gaia.cs.umass.edu/kurose_rossVideo: 2020, J.F. Kurose, All Rights ReservedPowerpoint: 1996-2020, J.F. Kurose, K.W. Ross, All Rights ReservedOverview. What is the Internet? What is a protocol?Network edgeNetwork corePerformance: loss, delay, throughputProtocol layers, service modelsSecurityHistory