Walrand Lecture 1EECS 228aEECS 228a – Lecture 1Overview: NetworksJean Walrandwww.eecs.berkeley.edu/~wlrFall 2002EECS228a - Walrand 2Course InformationInstructor: Jean Walrandn Office Hours: M-Tu 1:00 - 2:00Time/Place: MW 2:00-3:30 in 285 CoryHome Page:n http://www-inst.eecs.berkeley.edu/~ee228aEECS228a - Walrand 3TopicsOverview [1 week]Economics of Networks [4]Routing [4]Congestion Control [2.5]Traffic Models [2.5]Review [1]Theoretical backgroundState of the art EECS228a - Walrand 4DetailsGrading:n In class presentations: 50%n Project: 50% - Original research on selected topicMaterial:n Lecture Slides and Notesn Research PapersEECS228a - Walrand 5OverviewNetwork ExamplesNetwork ComponentsInternetworkingInternetOther NetworksPacketsTransportWeb BrowsingTelephone CallResource Sharing – MultiplexingProtocolsIETFEECS228a - Walrand 6Network ExamplesTeleglobe Communications Corporation – Fiber + SatelliteWalrand Lecture 1EECS 228aEECS228a - Walrand 7Network ExamplesGlobal Crossing CorporationEECS228a - Walrand 8Network ExamplesKPNQWESTEECS228a - Walrand 9Network ExamplesWilliams CommunicationsEECS228a - Walrand 10Network ExamplesPalo Alto NetworkEECS228a - Walrand 11Network ComponentsLink: carry bits from one place to another (or maybe to many other places)Switch/router: move bits between links, forming internetworkHost: communication endpoint (workstation, PDA, cell phone, toaster, tank)EECS228a - Walrand 12Network ComponentsFibersCat5 UnshieldedTwisted PairsCoaxial CableLinksWirelessWalrand Lecture 1EECS 228aEECS228a - Walrand 13Network ComponentsEthernet Network Interface CardEECS228a - Walrand 14Network ComponentsEthernetEECS228a - Walrand 15Network ComponentsEthernet is a broadcast-capable, multi-accessLANLink: EthernetEECS228a - Walrand 16Network ComponentsTelephone Switch Large RouterEECS228a - Walrand 17Network with RoutersLANs interconnected by routersLAN1LAN2LAN3InternetR1R2R3R4EECS228a - Walrand 18InternetworkingProvides message delivery between multiple networks:Subnet 1Subnet 2ISP 2ISP 1Example: Subnet 1 = network of LANs of previous slideISP 1 = Sprint, ISP 2 = MCISubnet 2 = UCB networkWalrand Lecture 1EECS 228aEECS228a - Walrand 19The InternetA global network of networks all using a common protocol (IP, the Internet Protocol)Focus of this classA challenge to understand:n large scale (10’s of millions of users, 10’s of thousands of networks)n heterogeneity, irregular topology, decentralized managementEECS228a - Walrand 20Scale of Internet• Data from www.nw.comEECS228a - Walrand 21Other NetworksThe Telephone NetworkProcessor Interconnection NetworksATM NetworksCable-TV NetworksEECS228a - Walrand 22PacketsABA | B | ...B → port 2123A | B | ...A | B | ...EECS228a - Walrand 23Packets: Main IdeasThe switches have no memory of packets: scalabilityThe network is independent of the applications: flexibilityThe packet formats and addresses are independent of the technology: extensibilityEECS228a - Walrand 24TransportPacketsACKsWalrand Lecture 1EECS 228aEECS228a - Walrand 25Web BrowsingExampleLocating Resource: DNSConnectionEnd-to-endPacketsBitsPoints to rememberEECS228a - Walrand 26Click Link or URLget content from localor remote computerURL:http://www.google.com/stringSpecifies- Protocol: http- Computer: www.google.com- StringComputer (server) selects contents based on stringWeb: ExampleEECS228a - Walrand 27Web: Locating Resourcewww.google.com is the name of a computerNetwork uses IP addressesTo find the IP address, the application uses a hierarchical directory service called theDomain Name Systemlocalcomhostwww.google.com?IP = a.b.c.dIP = a.b.c.dwww.google.com?EECS228a - Walrand 28Web: ConnectionThe protocol (http) sets up a connectionbetween the host and cnn.com to transfer the pageThe connection transfers the page as a byte stream, without errors: pacing + error controlHostcnn.comconnectOKgetpagepage;closeEECS228a - Walrand 29Web: End-to-endThe byte stream flows from end to end across many links and switches: routing (+ addressing)That stream is regulated and controlled by both ends: retransmission of erroneous or missing bytes; flow controlEnd-to-end pacing andflow controlRoutingwww.google.comhostEECS228a - Walrand 30Web: PacketsThe network transports bytes grouped into packetsThe packets are “self-contained” and routers handle them one by oneThe end hosts worry about errors and flow control:n Destination checks packet for errors (using error detection code CKS) and sends ACKs with sequence number #n Source retransmits packets that were notCA|B|#,CKS|bytesB Cwww.google.comIP address: AHostIP address: BDestinationNext HopWalrand Lecture 1EECS 228aEECS228a - Walrand 31Web: BitsEquipment in each node sends the packets as a string of bitsThat equipment is not aware of the meaning of the bits01011...011...110Transmitter Physical Medium Receiver01011...011...110OpticalCopperWirelessEECS228a - Walrand 32Web: Points to rememberSeparation of tasksn send bits on a link: transmitter/receiver [clock, modulation,…]n send packet on each hop [framing, error detection,…]n send packet end to end [addressing, routing]n pace transmissions [detect congestion]n retransmit erroneous or missing packets [acks, timeout]n find destination address from name [DNS]Scalabilityn routers don’t know about connectionsn names and addresses are hierarchicalEECS228a - Walrand 33Telephone CallTelephone NetworkDialing a NumberSetting up a CircuitPhone ConversationReleasing the CircuitEECS228a - Walrand 34Telephone Network5ESS (Lucent)DMS100 (Nortel)EECS228a - Walrand 35Telephone NetworkEECS228a - Walrand 36Telephone NetworkLogic Diagram:Walrand Lecture 1EECS 228aEECS228a - Walrand 37Dialing a NumberA Off-HookS1 ListensA dialsS1 RegistersABS1EECS228a - Walrand 38Setting Up a CircuitABringCircuit = capacity to carry one phone call (shown by thin lines)Circuit is allocated to the call between A and BCircuits are not shared; they are dedicated. EECS228a - Walrand 39Phone ConversationABVoice signals use the reserved circuitsEECS228a - Walrand 40Release CircuitsABA or B goes Off-HookCircuits get releasedEECS228a - Walrand 41Resource Sharing - MultiplexingNetworks are shared resourcesSharing viamultiplexingFundamental Question:how to achieve controlled sharingEECS228a - Walrand 42MultiplexingMethods for sharing a communication channelTradeoff between utilization and predictabilityCommon Approaches:n TDM (time-division multiplexing)n Statistical
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