Balaji Prabhakar

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Spring 2011 A history of big routers (slides from Nick McKeowns EE 384X presentation). EE384M Network Algorithms. Balaji Prabhakar. Outline. What is an Internet router? What limits performance: Memory access time The early days: Modified computers Programmable against uncertainty - PowerPoint PPT Presentation

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  • Balaji Prabhakar

    EE384MNetwork Algorithms

  • OutlineWhat is an Internet router?What limits performance: Memory access timeThe early days: Modified computersProgrammable against uncertaintyThe middle years: Specialized for performanceNeeded new architectures, theory, and practiceSo how did we do?Simple model breaking down

  • Definitions12345678N RN = number of linecards. Typically 8-32 per chassisR = line-rate. 1Gb/s, 2.5Gb/s, 10Gb/s, 40Gb/s, 100Gb/s

    Capacity of router = N x R

  • What a Big Router Looks LikeCisco GSR 12816Juniper T6406ft192ftCapacity: 640Gb/s Power: 5kW3ft2.5ft19Capacity: 320Gb/s Power: 3kW

  • What Multirack Routers Looks LikeCisco CRS-1Juniper T1600 + TX Matrix

  • Lookup internet addressCheck and update ageCheck and update checksum

  • Router Control and ManagementBarebones Router

  • Barebones Router

  • Barebones Router

  • BottlenecksMemory, memory,

  • OutlineWhat is an Internet router?What limits performance: Memory access timeThe early days: Modified computersProgrammable against uncertaintyThe middle years: Specialized for performanceNeeded new architectures, theory, and practiceSo how did we do?Simple model breaking down

  • Early days: Modified ComputerRRRRRRRRMust run at rate N x R

  • 2nd Generation Router

  • Early days: Modified ComputerFunction more important than speed

    1993 (WWW) changed everything

    We badly neededSome new architectureSome theorySome higher performance

  • N x R3rd Generation Router: Switch

  • Arbiter

  • Arbiter

  • 4th Generation Router Multirack; optics insideSwitchLinecardsOptical links100sof metres

  • Alcatel 7670 RSPJuniper TXTXMore 4th Generation RoutersAvici TSRCisco CRS-1

  • Example of TheoryTheres something special about 2

  • Case 1: Placing callsA crosspoint switch supports all permutationsSo it is non-blockingBut it needs N2 crosspointsCrosspoint switch

  • Case 1: Placing CallsUncertainty costsIf I give you the permutation, you can route it.If I give you entries one at a time, you cant.Clos (1950s): But if you make it run 2 times fasteryou can route calls one at a time.

  • Case 2: MimickingN x R

  • Case 2: Mimicking1 x R

  • Are they equivalent?No.

  • Case 2: MimickingAlgorithm

  • Now are they equivalent?

  • Case 3: Are they equivalent?

  • Case 4: Routing packets with uncertainty0.1 0.2 0.5 0.20.3 0.1 0.3 0.30.5 0.2 0.1 0.20.1 0.5 0.1 0.3RatesBut we dont know the rates (they are always changing) If you know the rates, you can find a sequence of permutations: 0 0 1 00 1 0 00 0 0 11 0 0 00 0 1 01 0 0 00 0 0 10 1 0 01 0 0 00 0 1 00 0 0 10 1 0 0=

  • Case 4: Routing packets with uncertainty

  • Case 5: Load-balancing Load-balancing to support all rate matrices:Requires the network to run 2 times fasterE.g. the VL2 (Valiant Load balancing) architecture for Data Centers

    **