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  • Scheduling Techniques for Hybrid Circuit/Packet

    NetworksHe Liu, Matthew K. Mukerjee, Conglong Li, Nicolas Feltman,

    George Papen, Stefan Savage, Srinivasan Seshan, Geoffrey M. Voelker, David G. Andersen, Michael Kaminsky, George Porter, and Alex C. Snoeren

  • Hybrid circuit/packet networks: Can we get best of both?

    Circuit Switching Packet Switching

    High link rate

    Low link rate

    Limits on num flows+ Explicit flow setup

    Any-to-any communication

    This talk: commun. restricted to pairs

    + non-trivial circuit reconfig time

  • Hybrid networks in datacenters*

    *Helios [SIGCOMM 10], c-Through [SIGCOMM 10], Flyways [SIGCOMM 11],

    RACK RACK RACK RACK RACK RACK RACK RACK

    Circuit Packet

  • Hybrid networks in datacenters*

    *Helios [SIGCOMM 10], c-Through [SIGCOMM 10], Flyways [SIGCOMM 11],

    A B CABC

    Datacenter workloadsare skewed

    Senders

    Receivers

  • Senders

    ReceiversHybrid networks in datacenters*

    *Helios [SIGCOMM 10], c-Through [SIGCOMM 10], Flyways [SIGCOMM 11],

    A B CABC

    Prior work showsmajor benefits

    (Keep circuits busy!)

  • Hybrid networks in datacenters*

    *Helios [SIGCOMM 10], c-Through [SIGCOMM 10], Flyways [SIGCOMM 11],

    Packet switch as escape hatch

    for difficult demands

    Need an explicit sequence of circuit

    configurations

  • Hybrid networks in datacenters*

    How do proposed hybrid networks schedule demand?They dont! They use an oracle

    *Helios [SIGCOMM 10], c-Through [SIGCOMM 10], Flyways [SIGCOMM 11],

  • Does prior scheduling work help?

    iSLIP BvN

    Works per-packet (cant identify difficult to schedule demands)

    Works on all demand simultaneously

    (can identify difficult demands)

    Both assume circuit reconfig is free (use many configurations)

    (Fast heuristic per-packet) Optimal

  • Does prior scheduling work help?BvN

    Both assume circuit reconfig is free (use many configurations)

    Time

    iSLIP

  • Contribution: Solstice

    Characterizing

    Optimal formulation and bounds

    A fast, heuristic-based hybrid scheduler

    of Solstice: performs 2-3x better than previous solutions and within 14% of optimal up to a 128-port switch

    the hybrid scheduling problem

    Solstice

    Evaluation

  • Outline

    Model

    the hybrid scheduling problem

    Solstice

    Evaluation

  • Goal of hybrid scheduling

    ?

    A B CABC

    Schedule all demand in minimum duration

  • Goal of hybrid scheduling

    Schedule all demand in minimum duration

    duration = total circuit transmission time+

    number of configurations * circuit reconfig cost

    Configuration selection and duration

    What goes topacket switch

  • The hybrid scheduling problem

    ?

    A B CABC

  • Understanding circuitsKey properties

    of circuit switching

    Configuration

    Duration

    A B CABC

  • Understanding circuitsKey properties

    of circuit switching

    Configuration

    Duration

    Src Dest

    A

    B

    C

    A

    B

    C

    A B CABC

    A

    B

    C

    A

    B

    C

    Src Dest

    Configuration

    Duration

  • The hybrid scheduling problem

    ?Circuit Switch Packet Switch

    A

    B

    C

    A

    B

    C

    A B CABC

  • The hybrid scheduling problem

    ?Circuit Switch Packet Switch

    A

    B

    C

    A

    B

    C

    A B CABC

    A B CABC

    How to compute the output?

  • Outline

    Model

    The hybrid scheduling problem

    Solstice

    Evaluation

  • Solstice: intuition

    What can we take advantage of?

    Skew in workload (i.e., large + small demands)

    Circuit switch is efficient for large demands

    Packet switch is efficient for small demands

  • Solstice: key ideaSchedule largedemands first

    on circuit

    A B CABC

    D

    D

  • Solstice: key ideaSchedule largedemands first

    on circuit

    Circuit SwitchLoop

    A B CABC

    D

    D

    A

    B

    C

    A

    B

    C

    D D

  • Solstice: key idea

    Circuit Switch

    A B CABC

    D

    D

    Schedule largedemands first

    on circuitLoop

    A

    B

    C

    A

    B

    C

    D D

    A

    B

    C

    A

    B

    C

    D D

  • Solstice: key ideaTerminate when

    remainder can be served by

    packet switch

    Circuit Switch

    A B CABC

    D

    D

    A

    B

    C

    A

    B

    C

    D D

    A

    B

    C

    A

    B

    C

    D D

    Packet SwitchA B C

    ABC

    D

    D

  • Solstice: key idea

    Large demand alwayson circuit switch

    (efficient)

    Small demand alwayson packet switch

    (efficient)Circuit SwitchA

    B

    C

    A

    B

    C

    D D

    A

    B

    C

    A

    B

    C

    D D

    Packet SwitchA B C

    ABC

    D

    D

  • Solstice: example

    A B CABC

    D E

    DE

  • Solstice: exampleTotal

    Duration

    0Reconfig time = 2.5

    . 5 40 . 5 5 . . 40 5 . . . 10 4045 5 . . . . 40 10 . .

  • Solstice: exampleServableon Packet

    0Total

    Duration

    0Reconfig time = 2.5 Packet BW = 1/10

    . 5 40 . 5 5 . . 40 5 . . . 10 4045 5 . . . . 40 10 . .

  • Solstice: exampleServableon Packet

    0Threshold

    32Total

    Duration

    0Reconfig time = 2.5 Packet BW = 1/10

    . 5 40 . 5 5 . . 40 5 . . . 10 4045 5 . . . . 40 10 . .

  • Solstice: exampleServableon Packet

    0Threshold

    32Total

    Duration

    0Reconfig time = 2.5 Packet BW = 1/10

    . 5 40 . 5 5 . . 40 5 . . . 10 4045 5 . . . . 40 10 . .

  • . 5 40 . 5 5 . . 40 5 . . . 10 4045 5 . . . . 40 10 . .

    A

    B

    C

    A

    B

    C

    D

    E

    D

    E

    Solstice: exampleServableon Packet

    0Threshold

    32Total

    Duration

    0Reconfig time = 2.5 Packet BW = 1/10

    40

  • Solstice: exampleServableon Packet

    0Threshold

    32Total

    Duration

    0Reconfig time = 2.5 Packet BW = 1/10

    40

    A

    B

    C

    A

    B

    C

    D

    E

    D

    E . 5 . . 5 5 . . . 5 . . . 10 . 5 5 . . . . . 10 . .

  • Solstice: exampleServableon Packet

    0Threshold

    32Total

    Duration

    40Reconfig time = 2.5 Packet BW = 1/10

    40

    A

    B

    C

    A

    B

    C

    D

    E

    D

    E . 5 . . 5 5 . . . 5 . . . 10 . 5 5 . . . . . 10 . .

  • Solstice: exampleServableon Packet

    0Threshold

    32Total

    Duration

    42.5Reconfig time = 2.5 Packet BW = 1/10

    40

    A

    B

    C

    A

    B

    C

    D

    E

    D

    E . 5 . . 5 5 . . . 5 . . . 10 . 5 5 . . . . . 10 . .

  • Solstice: exampleServableon Packet

    4.25Threshold

    32Total

    Duration

    42.5Reconfig time = 2.5 Packet BW = 1/10

    40

    A

    B

    C

    A

    B

    C

    D

    E

    D

    E . 5 . . 5 5 . . . 5 . . . 10 . 5 5 . . . . . 10 . .

  • Solstice: exampleServableon Packet

    4.25Threshold

    16Total

    Duration

    42.5Reconfig time = 2.5 Packet BW = 1/10

    40

    A

    B

    C

    A

    B

    C

    D

    E

    D

    E . 5 . . 5 5 . . . 5 . . . 10 . 5 5 . . . . . 10 . .

    Threshold too large

  • Solstice: exampleServableon Packet

    4.25Threshold

    8Total

    Duration

    42.5Reconfig time = 2.5 Packet BW = 1/10

    40

    A

    B

    C

    A

    B

    C

    D

    E

    D

    E . 5 . . 5 5 . . . 5 . . . 10 . 5 5 . . . . . 10 . .

  • Solstice: example

    A

    B

    C

    A

    B

    C

    D

    E

    D

    E

    Servableon Packet

    4.25Threshold

    8Total

    Duration

    42.5Reconfig time = 2.5 Packet BW = 1/10

    40

    A

    B

    C

    A

    B

    C

    D

    E

    D

    E . 5 . . 5 5 . . . 5 . . . 10 . 5 5 . . . . . 10 . .

    Incompleteconfiguration

  • Solstice: exampleServableon Packet

    4.25Threshold

    4Total

    Duration

    42.5Reconfig time = 2.5 Packet BW = 1/10

    40

    A

    B

    C

    A

    B

    C

    D

    E

    D

    E . 5 . . 5 5 . . . 5 . . . 10 . 5 5 . . . . . 10 . .

  • Solstice: example

    A

    B

    C

    A

    B

    C

    D

    E

    D

    E

    Servableon Packet

    4.25Threshold

    4Total

    Duration

    42.5Reconfig time = 2.5 Packet BW = 1/10

    40

    A

    B

    C

    A

    B

    C

    D

    E

    D

    E

    A

    B

    C

    A

    B

    C

    D

    E

    D

    E

    . 5 . . 5 5 . . . 5 . . . 10 . 5 5 . . . . . 10 . .

    MultipleConfigs

  • . 5 . . 5 5 . . . 5 . . . 10 . 5 5 . . . . . 10 . .

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