AS calable Switch for Service Guarantees by Y1CSu7R

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									 A Scalable Switch for
  Service Guarantees

Bill Lin (University of California, San Diego)
      Isaac Keslassy (Technion, Israel)
                                            Motivation
        Scalability: Traffic demands growing, driven in
         part by increasing broadband adoption
              10x increase in broadband subscription in just last 3
               years, already over 100 million subscribers
              1.25-2.4 Gbps fiber to homes emerging (GPON,
               GEPON, EPON, BPON …)
        Service Guarantees: Operators need
         bandwidth partitioning capabilities
              Provide guaranteed rates in service-level agreements
              Enable logical partitioning of converged networks
              Traffic engineering in general

IEEE Hot Interconnects XIII, August 17-19, 2005                        2
                                 Router Wish List
        Scalable in line rates and number of linecards
              e.g. R = 160 Gbps (new packet every 2ns), thousands
               of linecards, petabit capacity
              No centralized scheduler
              No per-packet dynamic switch reconfigurations
              Low complexity linecards

        Provide performance guarantees
              100% throughput guarantee
              Service guarantees
              No packet reordering

IEEE Hot Interconnects XIII, August 17-19, 2005                      3
                       Existing Architectures
        Output-Queueing (OQ) Switch
              Well-known rate guarantees possible with Weighted
               Fair Queueing or Deficit Round-Robin scheduling
                • But OQ switches require speedup of N
        Crossbar Switches, using Input-Queueing (IQ) or
         Combined Input-Output Queueing (CIOQ)
           OQ emulation possible
                 • But expensive centralized scheduling and per-packet
                   dynamic switch reconfigurations
              Birkhoff-von Neumann decomposition
                 • If traffic matrix known, can provide rate guarantees with
                   distributed scheduling, but still requires per-packet dynamic
                   switch reconfigurations

IEEE Hot Interconnects XIII, August 17-19, 2005                                    4
         Existing Architectures (cont’d)
        Load-Balanced Switches
              Chang et al., “Load balanced Birkhoff-von Neumann
               switches, Part I: one-stage buffering”, Computer
               Communications, 2002
              Keslassy et al., “Scaling Internet routers using optics”,
               ACM SIGCOMM 2003
                 • A key idea: fixed configuration uniform meshes in
                   optics, no dynamic switch reconfigurations
                 • Showed 100 Tb/s load-balanced router with R = 160 Gbps
                   and N = 640 linecards
              Showed 100% throughput for “best effort” traffic, but
               no service guarantees

IEEE Hot Interconnects XIII, August 17-19, 2005                             5
                                              This Talk
       Presents the Interleaved Matching Switch (IMS)
       Like a load-balanced switch, use fixed
        configuration uniform meshes, implemented
        with an optical fabric
             No arbitrary per-packet switch reconfiguration
       Can emulate any IQ or CIOQ switch
       Can emulate a Birkhoff-von Neumann switch
             If traffic matrix known, can ensure 100% throughput,
              service guarantees, and packet ordering
             Show we can use O(1) distributed online scheduling


IEEE Hot Interconnects XIII, August 17-19, 2005                      6
        Generic Load-Balanced Switch
         Using Fixed Configuration Uniform Meshes
                  Linecards                       Linecards           Linecards

 3
 2
 1         R                       R/N                          R/N               R
                        In         R/N
                                                                        Out
                                                                R/N
                               R/N                            R/N


                                 R/N                           R/N
           R                                                                      R
                        In       R/N                           R/N      Out
                                 R/N                           R/N


                               R/N                            R/N

                                   R/N                          R/N
           R                                                                      R
                        In         R/N                          R/N     Out

IEEE Hot Interconnects XIII, August 17-19, 2005                                       7
        Generic Load-Balanced Switch
         Using Fixed Configuration Uniform Meshes
                  Linecards                       Linecards           Linecards

           R                       R/N                          R/N               R
                        In         R/N
                                                                        Out
                                                          1     R/N
                               R/N                            R/N


                                 R/N                           R/N
           R                                                                      R
                        In       R/N                           R/N      Out
                                 R/N                      2    R/N


                               R/N                            R/N

                                   R/N                          R/N
           R                                                                      R
                        In         R/N                          R/N     Out
                                                          3

IEEE Hot Interconnects XIII, August 17-19, 2005                                       8
        Generic Load-Balanced Switch
         Using Fixed Configuration Uniform Meshes
                  Linecards                       Linecards           Linecards

           R                       R/N                          R/N               R
                        In         R/N
                                                                        Out
                                                                R/N
                               R/N                            R/N
                        Many Fabric Options (any spreading device)

                         Space: Full uniform mesh
                             R/N                               R/N
           R                                                                      R
                        InWavelength: Static WDM
                            R/N                               R/N      Out
                         Time: Round-robin switches
                             R/N                               R/N

                        Just need fixed uniform rate channels at R/N
                               R/N                            R/N
                                                       R/N
                        No dynamic switch reconfigurations
                             R/N
           R                                                                      R
                        In         R/N                          R/N     Out

IEEE Hot Interconnects XIII, August 17-19, 2005                                       9
             From Load-Balanced Switch
                  Linecards                       Linecards           Linecards

           R                       R/N                          R/N               R
                        In         R/N
                                                                        Out
                                                                R/N
                               R/N                            R/N


                                 R/N                           R/N
           R                                                                      R
                        In       R/N                           R/N      Out
                                 R/N                           R/N


                               R/N                            R/N

                                   R/N                          R/N
           R                                                                      R
                        In         R/N                          R/N     Out

IEEE Hot Interconnects XIII, August 17-19, 2005                                       10
       To Interleaved Matching Switch
                        Linecards                       Linecards          Linecards

           R                                      R/N                R/N               R
                                                  R/N
                                                                             Out
                                                                     R/N
 Move main
                                            R/N                 R/N
 packet buffers
 to INPUT
                                              R/N                   R/N
           R                                                                           R
                                              R/N                   R/N      Out
                                              R/N                   R/N
                                   Add
                                   coordination
                                   slots R/N
                                         in MIDDLE             R/N

                                                  R/N                R/N
           R                                                                           R
                               Retain Fixed Configuration Meshes
                                         R/N               R/N               Out

IEEE Hot Interconnects XIII, August 17-19, 2005                                            11
                                       How It Works
        IMS works by emulating an IQ or CIOQ crossbar
         switch, but without per-packet dynamic
         switch reconfigurations (will show how centralized
         scheduling can be avoided later)




IEEE Hot Interconnects XIII, August 17-19, 2005               12
                                       How It Works
                        Linecards                       Linecards          Linecards

           R                    A2 A1             R/N                R/N               R
  A                                A1
                                                  R/N
                                                                             Out
                                A2 A1                                R/N
                                            R/N                 R/N


                                              R/N                   R/N
           R                       B1                                                  R
  B                             B2 B1         R/N                   R/N      Out
                                B2 B1         R/N                   R/N


                                            R/N                R/N

                                                  R/N                R/N
           R                    C2 C1                                                  R
  C                             C2 C1             R/N                R/N     Out
                                C2 C1

IEEE Hot Interconnects XIII, August 17-19, 2005                                            13
                                       How It Works
              Crossbar Switch                                   Interleaved Matching Switch
    Linecards              XBAR           Linecards             Linecards         Linecards Linecards
R       A2 A1 R                         R               R   R     A2 A1     R/N          R/N         R
           A1                                     Out                A1     R/N          R/N   Out
        A2 A1                                                     A2 A1
                                                                            R/N         R/N


R          B1 R                         R               R   R        B1 R/N             R/N          R
        B2 B1                                     Out             B2 B1 R/N             R/N    Out
        B2 B1                                                     B2 B1
                                                                            R/N         R/N

                                                                            R/N         R/N
R       C2 C1 R                         R               R   R     C2 C1                              R
        C2 C1                                     Out             C2 C1     R/N          R/N   Out
        C2 C1                                                     C2 C1     R/N          R/N


IEEE Hot Interconnects XIII, August 17-19, 2005                                                      14
                                       How It Works
              Crossbar Switch                                   Interleaved Matching Switch
    Linecards              XBAR           Linecards             Linecards         Linecards Linecards
R       A2 A1 R                         R               R   R     A2 A1     R/N          R/N         R
           A1                                     Out                A1     R/N          R/N   Out
        A2 A1                                                     A2 A1
                                                                            R/N         R/N


R          B1 R                         R               R   R        B1 R/N             R/N          R
        B2 B1                                     Out             B2 B1 R/N             R/N    Out
        B2 B1                                                     B2 B1
                                                                            R/N         R/N

                                                                            R/N         R/N
R       C2 C1 R                         R               R   R     C2 C1                              R
        C2 C1                                     Out             C2 C1     R/N          R/N   Out
        C2 C1                                                     C2 C1     R/N          R/N


IEEE Hot Interconnects XIII, August 17-19, 2005                                                      15
                                       How It Works
              Crossbar Switch                                    Interleaved Matching Switch
    Linecards              XBAR           Linecards              Linecards         Linecards Linecards
R       A2 A1 R                         R               R
                                                        B1   R     A2 A1     R/N     B1   R/N         R
           A1                                     Out                 A1     R/N     C1   R/N   Out
        A2                                                         A2                A1
                                                                             R/N          R/N


R                   R                   R               R
                                                        C1   R               R/N          R/N         R
        B2 B1                                     Out              B2 B1 R/N              R/N   Out
        B2 B1                                                      B2 B1
                                                                             R/N          R/N

                                                                             R/N          R/N
R       C2 C1 R                         R               R
                                                        A1   R     C2 C1                              R
        C2                                        Out              C2        R/N          R/N   Out
        C2 C1                                                      C2 C1     R/N          R/N


IEEE Hot Interconnects XIII, August 17-19, 2005                                                       16
                                       How It Works
              Crossbar Switch                         Interleaved Matching Switch
    Linecards              XBAR           Linecards   Linecards         Linecards Linecards
R       A2 A1 R           R        RB1   R     A2 A1              R/N          R/N         R
                                                                                           B1
           A1                 Out                 A1              R/N          R/N   Out
        A2    Differences with crossbar switch A2
                                                                  R/N         R/N
                No dynamic switch reconfigurations
                     
R             R           R        R
                                   C1    R          R/N         R/N                        R
                                                                                           C1
                             Out
        B2 B1  Departure times delayed by 2NB2 B1slots, N time R/N
                                              time R/N                               Out
        B2 B1                                B2 B1
                slots per mesh, otherwise same sequence
                                                    R/N         R/N

                                                        slot
                Packet transfers initiated at each time R/N to
                                                                             R/N
R                         R        R       R
        C2 C1 R next MIDDLE linecard in round-robin order
                                    A1          C2 C1                                      R
                                                                                           A1
        C2                    Out               C2       R/N                   R/N   Out
        C2 C1                                   C2 C1 R/N                      R/N


IEEE Hot Interconnects XIII, August 17-19, 2005                                            17
                                       How It Works
              Crossbar Switch                                   Interleaved Matching Switch
    Linecards              XBAR           Linecards             Linecards         Linecards Linecards
R       A2 A1 R                         R               R   R     A2 A1     R/N          R/N         R
           A1                                     Out                A1     R/N          R/N   Out
           A2                                                        A2
                                                                            R/N         R/N


R                   R                   R               R   R               R/N         R/N          R
        B2 B1                                     Out             B2 B1 R/N             R/N    Out
        B2 B1                                                     B2 B1
                                                                            R/N         R/N

                                                                            R/N         R/N
R       C2 C1 R                         R               R   R     C2 C1                              R
           C2                                     Out                C2     R/N          R/N   Out
        C2 C1                                                     C2 C1     R/N          R/N


IEEE Hot Interconnects XIII, August 17-19, 2005                                                      18
                                       How It Works
              Crossbar Switch                                    Interleaved Matching Switch
    Linecards              XBAR           Linecards              Linecards         Linecards Linecards
R       A2          R                   R               R
                                                        A1   R     A2        R/N          R/N         R
             A1                                   Out                   A1   R/N          R/N   Out
             A2                                                         A2
                                                                             R/N         R/N


R                   R                   R               R
                                                        B1   R               R/N     A1 R/N           R
        B2                                        Out              B2    R/N         B1 R/N     Out
        B2 B1                                                      B2 B1             C1
                                                                             R/N         R/N

                                                                             R/N         R/N
R       C2 C1 R                         R               R
                                                        C1   R     C2 C1                              R
           C2                                     Out                 C2     R/N          R/N   Out
        C2                                                         C2        R/N          R/N


IEEE Hot Interconnects XIII, August 17-19, 2005                                                       19
                                       How It Works
              Crossbar Switch                                   Interleaved Matching Switch
    Linecards              XBAR           Linecards             Linecards         Linecards Linecards
R            A2 R                       R               R   R        A2     R/N          R/N         R
             A1                                   Out                A1     R/N          R/N   Out
             A2                                                      A2
                                                                            R/N         R/N


R                   R                   R               R   R               R/N         R/N          R
           B2                                     Out                B2 R/N             R/N    Out
        B2 B1                                                     B2 B1
                                                                            R/N         R/N
              Crossbar MATCHINGS are INTERLEAVEDR/N  across    R/N
R             MIDDLE linecards (analogous to memory interleaving)
        C2 C1 R           R       R     R    C2 C1                                                   R
           C2                Out                C2 R/N          R/N                            Out
           C2                                   C2 R/N          R/N


IEEE Hot Interconnects XIII, August 17-19, 2005                                                      20
         IQ and CIOQ Switch Emulation
        An IMS can emulate any IQ or CIOQ switch.




IEEE Hot Interconnects XIII, August 17-19, 2005      21
           When Traffic Matrix is Known
        When traffic matrix is known, can perform
         Birkhoff-von Neumann decomposition offline

        Given any admissible traffic matrix

        Can decompose into a series of permutation
         matrices ( ) such that



         where
IEEE Hot Interconnects XIII, August 17-19, 2005       22
                                                  Example
        Consider following example:




        Use weighted fair queueing to schedule each
         permutation matrix   proportionally to its
         corresponding weight
IEEE Hot Interconnects XIII, August 17-19, 2005             23
Distributed Storage and Scheduling




        Distributed storage: each input linecard only
         stores its corresponding “rows”
        Distributed scheduling: each input linecard
         only responsible for scheduling its own VOQs
        O(1) time/hardware complexity: use deficit
         round-robin scheduling (many efficient variants)
IEEE Hot Interconnects XIII, August 17-19, 2005             24
    Birkhoff-von Neumann Emulation
        If traffic matrix known, an IMS can guarantee
         100% throughput and guaranteed flow rates
         when combined with Birkhoff-von Neumann
         decomposition and online fair scheduling




IEEE Hot Interconnects XIII, August 17-19, 2005          25
           Frame-Based Decomposition
        If traffic matrix  can be converted to an integer
         matrix by multiplying by an integer F, then 
         can be decomposed into F permutations

        Known decomposition algorithms (if F is integer
         multiple of N )
          Birkhoff-von Neumann: O( N3.5 )

          Slepian-Duguid: O( N3 )


        New efficient formulation using edge-coloring
          O( N2 log N)

IEEE Hot Interconnects XIII, August 17-19, 2005               26
                                        Conclusions
         Scalability
               IMS leverages scalability of fixed optical meshes
               If traffic matrix known, distributed online scheduling
                can achieve O(1) time and hardware complexity
         Emulation
               IMS can emulate any IQ or CIOQ switch under
                same speedup and matching
         Guarantees
               If traffic matrix known, can ensure 100% throughput,
                service guarantees, and packet ordering via
                Birkhoff-von Neumann switch emulation
               For integer matrices, new edge coloring formulation
IEEE Hot Interconnects XIII, August 17-19, 2005                          27
Thank You

								
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