Lecture 11Switching & ForwardingTOC: Switching & ForwardingSwitching: Why?Switching: TechniquesTechniques: Circuit-SwitchingTechniques: Packet-SwitchingTechniques: PS - DatagramDatagram: Layer 2 (e.g., Ethernet)Datagram: Layer 3 (e.g., IP)Datagram: Layer 3 (e.g., IP)Datagram: Layer 3 (e.g., IP)Datagram: Layer 3 (e.g., IP)Techniques: PS – Virtual CircuitTechniques: Source RoutingTechniques: ComparisonSwitching: CharacteristicsSwitching: ExamplesExamples: Cisco GSR - 12416Examples: Juniper M160Examples: Cisco 7600Examples: Cisco cat 6500Examples: Extreme - SummitExamples: Foundry - ServerIronSwitching: ArchitecturesArchitectures: GenericArchitectures: First GenerationArchitectures: Second GenerationArchitectures: Third GenerationArchitectures: Input FunctionsArchitectures: Output FunctionsArchitectures: Output Functions (ct)Architectures: Output QueuedArchitectures: Input QueuesNote: Head-of-line BlockingArchitectures: Virtual Output BuffersVOB: Full ThroughputVOB: Good Heuristic – i-SLIPArchitectures: Combined IN/OUTSwitching: SummaryWalrand Lecture 11EECS 122Lecture 11Switching & ForwardingEECS 122University of CaliforniaBerkeleyEECS 122 Walrand 2TOC: Switching & ForwardingWhy?Switching TechniquesSwitch CharacteristicsSwitch ExamplesSwitch ArchitecturesSummaryEECS 122 Walrand 3Direct vs. Switched Networks:Direct Network Limitations: Distance (coordination delay; propagation limitation) Number of hosts (collisions; shared bandwidth; address tables) Single link technology (cannot mix optical, wireless, …)Internetworking: Externality gain at low costSwitching: Why?Single linkn linksSwitchesDirect SwitchedEECS 122 Walrand 4Circuit-Switching (e.g., Telephone net.)Packet-Switching Datagram (e.g., IP, Ethernet) Virtual Circuits (e.g., MPLS, ATM) Source RoutingComparisonSwitching: TechniquesEECS 122 Walrand 5Mechanism:Techniques: Circuit-SwitchingLink divided into fixed,independent circuitsCircuit SwitchConnection listTime scale: connection(e.g., TDM, WDM)• Packets not switched independently (establish circuit before sending data)• Dedicated path and resources from source to destination• Setup time; low delays and guaranteed resources thereafterFeatures:EECS 122 Walrand 6Mechanism:Techniques: Packet-SwitchingWhole link shared byall packetsPacket Switch• Data separated into packets• Switching decision (output port) for each individual packet• Statistical multiplexing: Sum of peak rates may exceedlink bandwidth (as long as mean does not)Features:Walrand Lecture 11EECS 122EECS 122 Walrand 7Techniques: PS - DatagramGeneral idea: no connection establishment, but each packet contains enough info to specify destinationSwitches contain forwarding tables (but no per-connection “state”)Forwarding tables contain info on which outgoing port to use for each destinationTwo types of addressing: Layer 2 or Layer 3EECS 122 Walrand 8Datagram: Layer 2 (e.g., Ethernet)Flat address space (no structure)Forwarding table:Exact match of destination L2 addressabcdef12341234a 1b 4c 3d 2e 2f 2a 1b 1c 1d 2e 3f 4e|b|ToFromEECS 122 Walrand 9Datagram: Layer 3 (e.g., IP)L3-network (e.g., IP) Topological structure – match prefix Either fixed prefix length or longest matchE.g. 1E.g. 2E.g. 3Fixed1101000111001101Longest1100100110100111110100001100100010100000010000001101OtherABCDA’C’B’11010101110011100000EECS 122 Walrand 10Fixed1101000111001101Longest1100100110100111110100001100100010100000010000001101OtherABCDA’C’B’11010101110011100000Datagram: Layer 3 (e.g., IP)E.g. 111011001 matches 4 bits at A, 1 at B, 3 at C Æ A = LPM4 bits at A’ Æ A’ = EM11011001EECS 122 Walrand 11Fixed1101000111001101Longest1100100110100111110100001100100010100000010000001101OtherABCDA’C’B’11010101110011100000Datagram: Layer 3 (e.g., IP)E.g. 211001001 matches 3 bits at A, 1 at B, 7 at C Æ C = LPM11001001EECS 122 Walrand 12Datagram: Layer 3 (e.g., IP)E.g. 301100101 matches0 bit at A’ Æ B’0 bit at B, 0 at C, 2 at D Æ D = LPMFixed1101000111001101Longest1100100110100111110100001100100010100000010000001101OtherABCDA’C’B’1101010111001110000001100101Walrand Lecture 11EECS 122EECS 122 Walrand 13Techniques: PS – Virtual CircuitConnection setup establishes a path through switches A virtual circuit ID (VCI) identifies path Uses packet switching, with packets containing VCI VCIs are often indices into per-switch connection tables; change at each hop12341234VC1VC1VC1VC1VC2VC1VC2VC3VC2In, VC Out, VC1, 1 4, 11, 2 4, 32, 1 4, 2….EECS 122 Walrand 14Techniques: Source Routing1234123412341234123412344source3 44 3 44 3 4Each packet specifies the sequence of routers (or of output ports) from source to destinationEECS 122 Walrand 15Techniques: ComparisonlowlowhighRobustness*yesflexiblenoneResource reservationslowflexiblehighBandwidth utilizationnonelowhighForwarding costCircuit switchingVirtual circuit switchingDatagram*The idea is that in case of failure, circuit and VC are lost; datagram routing can adapt after routing update ….EECS 122 Walrand 16Switching: CharacteristicsPorts Fast Ethernet, OC-3, ATM, …Protocols ST, Link Agg., VLAN, OSPF, RIP, BGP, VPN, Load Balancing, WRED, WFQPerformance Throughput, Reliability, Power, …EECS 122 Walrand 17Switching: ExamplesJuniper M160Cisco “GSR”Cisco “7600”Cisco “catalyst 6500”Extreme “Summit”Foundry “ServerIron”EECS 122 Walrand 18Examples: Cisco GSR - 12416WAN Router – Large throughput; SONET linksUp to 16 line cards at 10 Gbps eachCrossbar FabricLine Cards: 1-port OC-192c4-port OC48cMany others (ATM, Ethernet, …)Cisco GSR 124166ft19”2ftWalrand Lecture 11EECS 122EECS 122 Walrand 19Examples: Juniper M160WAN Router – Large throughput; SONET linksCrossbar FabricLine Cards: 1-port OC-192c4-port OC48cMany others (ATM, Ethernet, …)Juniper M1603ft2.5ft19”Capacity: 80Gb/sPower: 2.6kWEECS 122 Walrand 20Examples: Cisco 7600MAN-WAN RouterUp to 128 Gbps with Crossbar Fabric10Mbps – 10Gbps LAN InterfacesOC-3 to OC-48 SONET InterfacesMPLS, WFQ, LLQ, WRED, Traffic ShapingEECS 122 Walrand 21Examples: Cisco cat 6500From LAN to Access48 to 576 10/100 Ethernet Interfaces10 GE, OC-3, OC-12, OC-48, ATMQoS, ACLLoad Balancing; VPNUp to 128Gbps (with crossbar)L4-7 SwitchingVLANIP Telephony (E1, T1, inline-power Ethernet)SNMP, RMONEECS 122 Walrand 22Examples: Extreme - Summit48 10/100 ports2 GE (SX, LX, or LX-70)17.5Gbps non-blocking10.1 MppsWire speed L2Wire speed L3
View Full Document
Unlocking...