Fundamentals of Mobile and Pervasive Computing

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					“Improving Fairness for Multi-Hop Bursts in
    Optical Burst Switching Networks”




Asia Pacific Advanced Network 2007, 27-31 August 2007,
            Xi’An, People’s Republic of China.
                                   Tananun Orawiwattanakul
                                   Yusheng Ji
                                   Yongbing Zhang
                 Topics


• Optical Burst Switching (OBS) Networks

• Hop Based Preemption (HBP)

• Numerical results

• Future works
         Optical Burst Switching (OBS)




   L                                                               L
   A                                                               A
   N    Edge Switch   Core Switch     Core Switch   Edge Switch    N
Users
                             OBS                                  Users
                            Network
Optical Burst Switching (OBS)




                        Control Wavelengths




                        Data Wavelengths
                       Optical Burst Switching (OBS)




                        C
                                               Control Wavelengths


Electronic   Optical
                                               Data Wavelengths
               DB
IP Packets
Optical Burst Switching (OBS)




              C
                         Control Wavelengths




 DB                      Data Wavelengths


      Offset Time
Optical Burst Switching (OBS)



              Optic   Electronic Process




                        Optic



                C         C
                                                               Control Wavelengths

                           Reserve this wavelength for the incoming data burst

  DB                                                           Data Wavelengths


       Offset Time
Optical Burst Switching (OBS)



     Optic        Electronic Process




                    Optic



       C              C     C
                                       Control Wavelengths

               DB
              Full Wavelength
                Conversion
        DB                             Data Wavelengths


             Offset Time
Optical Burst Switching (OBS)




                           C
                                Control Wavelengths




                  DB            Data Wavelengths


                  Offset Time
Optical Burst Switching (OBS)




                      Optical   Electronic
                       DB
                                IP Packets
     General Networks



     S1
                Buffer
                    S4           S5


S2         S3




 General Networks -> Electrical Buffer
Loss occurs only during high traffic load
                      Challenge of OBS


                                Offset Time1

                                                    Offset Time5
                                                                   DB5
            C1   C2                C4          C5

                      C3                                                   Control Channels
                                             Offset Time1
                                                                     DB4
                           Offset Time1
                                                                   DB1
                                        Offset Time1                       Data Channels
                                                                     DB3
                              Offset Time1                          DB2



            T1   T2   T3            T4                              T5
                                                                                              Time




No Buffer -> Contention occurs -> High Losses even in the light traffic load

      The longer path -> The higher probability of Loss -> Unfairness
       Hop Based Preemption (HBP)

• The objective of HBP is to improve fairness for multi-
hop bursts in OBS networks.

• The burst that has traveled through many nodes
and has a high possibility to arrive at a destination can
preempt a channel from other scheduled bursts.

• HBP support non/full/limited wavelength conversion
networks.

• HBP is implemented only in core switches.
                                                  HBP

                                              Offset Time5   Contending Burst
                                                                DB5
C1    C2                   C4            C5

                                                                                Control Channels
            C3

                                     Offset Time1
                                                                     DB4
                 Offset Time1
                                                               DB1
                                Offset Time1                                    Data Channels
                                                                     DB3
                     Offset Time1
                                                                 DB2



                                                                                                   Time
T1   T2    T3               T4                                 T5
             HBP Scheme Parameters
Parameters                           Description

                No. of hops between ingress switch of burst and
   Hp
              corresponding switch.

              No. of hops between corresponding switch and egress
   Ho
              switch of burst.
   Wp          Weight of Hp ( >=0)

   Wo          Weight of Ho ( >=0)

              The minimum ratio of No. of hops that burst has traveled
    M         through and No. of hops between burst’s ingress and egress
              switches

    I         Hop Index

    T         Threshold ( >=0)
                                HBP
          Contending will be dropped if

          HpContending / (HpContending + HoContending) < M   M = 1/2
                                                             3/ (3+3) = 1/2

               Hp = 3                          Ho = 3

                           Contending Burst
                                 DB5    I5
Source5                                                      Destination5

                           Scheduled Bursts
                                 DB4    I4
                                 DB1    I1
                                 DB3    I3
                                 DB2    I2
                              HBP
                   I = (Hp * Wp ) - (Ho * Wo )

                          Wp = Wo = 1
          I of the contending burst = 3-3 (Hp-Ho) = 0

          Hp = 3                                 Ho = 3

                         Contending Burst
                               DB5

Source5                              I5 = 0               Destination5

                         Scheduled Bursts
                               DB4

                               DB1

                               DB3

                               DB2
                                       HBP

    The contending burst wins the contention.

                    Hp = 3                               Ho = 3

                                  Contending Burst
                                        DB5

Source5                                       I5 = 0                   Destination5

                                  Scheduled Bursts
                                        DB4    I4 = 1
                                        DB1    I1 = -1   Least I
                                        DB3    I3 = 3
                                        DB2    I2 = 0


          The contending burst can preempt the channel of the original burst if
                                     I5 – I1 >= T
                                     When T = 1
                                      0-(-1) = 1
                                                    HBP
The corresponding switch cancels the original wavelength
reservation for the original burst and instead allocates the
          wavelength for the contending burst.
                                                Offset Time5   Contending Burst
                                                                  DB5
  C1    C2                   C4            C5

                                                                                  Control Channels
              C3

                                       Offset Time1
                                                                    DB4
                   Offset Time1
                                                                  DB5
                                                                 DB1
                                  Offset Time1                                    Data Channels
                                                                    DB3
                       Offset Time1
                                                                   DB2



                                                                                                     Time
 T1    T2    T3               T4                                 T5
               Numerical Results

• Simulated on Optical Internet Research Center’s
(OIRC) optical burst switching simulator based on
ns-2.

• Based on NSF and ARPA networks

• No losses in control channels

• Bandwidth per wavelength = 1 Gbps and the
processing time of a BCP at each switch = 0.01
msec

• Hybrid burst assembly
                                NSF Network


                                                                800
                                                                      11
                                                         10
                                        2400               800             300
                         2800                             500
          0                                           700
1100                                            7            8             13
              1600                                                500
                     3           800    6   700
1                                                         900               300
              1000       600 4
                                               2000                   12
                                 1100
    600
          2                        5                  9
                     2000                   1200
                             NSF Network

  Burst loss
probability (%)
0.06
0.05
0.04
0.03
0.02
0.01
  0
         3 4 5         3      4 5    3      4 5   3      4 5   3      4 5
       (General OBS)       1:1:1         1:1:2        1:0:1        1:0:2
                                    No. of hops
                                    (Wp:Wo:T )
                         NSF Network


Total burst loss
probability (%)
  0.0275

   0.027

  0.0265

   0.026

  0.0255

   0.025
           General_OBS   1:1:1    1:1:2    1:0:1   1:0:2
                                 Wp:Wo:T
                    ARPA Network



    0       5   8              9   12   16   18

        3                          13
1           6             10                      19
                                   14
        4

    2       7        11            15   17   20
                               ARPA Network

  Burst loss
probability (%)
0.25

 0.2

0.15

 0.1

0.05

  0
       3 4 5 6 7 8 9     3 4 5 6 7 8 9   3 4 5 6 7 8 9   3 4 5 6 7 8 9   3 4 5 6 7 8 9
         (General OBS)        (1:1:1)         (1:1:2)         (1:0:1)         (1:0:2)
                                          No. of hops
                                          (Wp:Wo:T )
                         ARPA Network

Total burst loss
probability (%)
  0.064
  0.062

    0.06

  0.058
  0.056

  0.054

  0.052

    0.05
           General_OBS   1:1:1     1:1:2   1:0:1   1:0:2
                                 Wp:Wo:T
                 Future works



• Resolve more complicated unfairness issues,
such as unfairness caused by bottle-neck links.

• Provide flow level fairness

• Decrease the total loss probability.

				
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posted:9/17/2012
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