1. “Improving Fairness for Multi-Hop Bursts in Optical Burst Switching Networks” Tananun Orawiwattanakul Yusheng Ji Yongbing Zhang Asia Pacific Advanced Network 2007, 27-31 August 2007, Xi’An, People’s Republic of China.

2. Topics Optical Burst Switching (OBS) Networks Hop Based Preemption (HBP) Numerical results Future works

3. LANLAN Optical Burst Switching (OBS) Core Switch Edge Switch Users LANLAN OBS Network

4. Optical Burst Switching (OBS) Control Wavelengths Data Wavelengths

5. Optical Burst Switching (OBS) DB C Control Wavelengths Data Wavelengths Electronic IP Packets Optical

6. Optical Burst Switching (OBS) DB C Offset Time Control Wavelengths Data Wavelengths

7. Optical Burst Switching (OBS) DB Offset Time C OpticElectronic Process Optic C Reserve this wavelength for the incoming data burst Control Wavelengths Data Wavelengths

8. Optical Burst Switching (OBS) C OpticElectronic Process Optic C CDB Full Wavelength Conversion DB Offset Time Control Wavelengths Data Wavelengths

9. Optical Burst Switching (OBS) DB Offset Time C Control Wavelengths Data Wavelengths

10. Optical Burst Switching (OBS) DB OpticalElectronic IP Packets

11. General Networks S5S5 S1S1 S2S2 S3S3 S4S4 Buffer General Networks -> Electrical Buffer Loss occurs only during high traffic load

12. DB4 Data Channels DB1 DB3 DB2 Time Control Channels C1C2 C3 C4 T1T2T3T4T5 Offset Time1 C5 DB5 Offset Time5 No Buffer -> Contention occurs -> High Losses even in the light traffic load The longer path -> The higher probability of Loss -> Unfairness Challenge of OBS

13. 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.

14. HBP DB4 Data Channels DB1 DB3 DB2 Time Control Channels C1C2 C3 C4 T1T2T3T4T5 Offset Time1 C5 DB5 Offset Time5 Contending Burst

15. HBP Scheme Parameters ParametersDescription Hp No. of hops between ingress switch of burst and corresponding switch. Ho No. of hops between corresponding switch and egress switch of burst. Wp Weight of Hp ( >=0) Wo Weight of Ho ( >=0) M The minimum ratio of No. of hops that burst has traveled through and No. of hops between burst ’ s ingress and egress switches IHop Index TThreshold ( >=0)

16. HBP DB4 DB1 DB3 DB2 DB5 Contending Burst I5I5 I4I4 I1I1 I3I3 I2I2 Scheduled Bursts DB5 Contending Burst I5I5 Source5Destination5 Hp = 3Ho = 3 Contending will be dropped if HpContending / (HpContending + HoContending) < M M = 1/2 3/ (3+3) = 1/2

17. HBP DB4 DB1 DB3 DB2 DB5 Contending Burst I 5 = 0 Scheduled Bursts DB5 Contending Burst Source5Destination5 Hp = 3Ho = 3 I = (Hp * Wp ) - (Ho * Wo ) Wp = Wo = 1 I of the contending burst = 3-3 (Hp-Ho) = 0

18. HBP DB4 DB1 DB3 DB2 DB5 Contending Burst I 5 = 0 Scheduled Bursts DB5 Contending Burst Source5Destination5 Hp = 3Ho = 3 I 4 = 1 I 1 = -1 I 3 = 3 I 2 = 0 Least I The contending burst can preempt the channel of the original burst if I 5 – I 1 >= T When T = 1 0-(-1) = 1 The contending burst wins the contention.

19. HBP The corresponding switch cancels the original wavelength reservation for the original burst and instead allocates the wavelength for the contending burst. DB4 Data Channels DB3 DB2 Time Control Channels C2 C3 C4 T2T3T4T5 Offset Time1 DB1 C1 T1 Offset Time1 C5 DB5 Offset Time5 Contending Burst DB5

20. 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

21. NSF Network

24. ARPA Network

27. Future works Resolve more complicated unfairness issues, such as unfairness caused by bottle-neck links. Provide flow level fairness Decrease the total loss probability.