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

1. “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

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

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

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

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

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

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

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

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

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

11. General Networks S1 Buffer S4 S5 S2 S3 General Networks -> Electrical Buffer Loss occurs only during high traffic load

12. Challenge of OBS Dropped Offset Time5 DB5 C5 Offset Time1 C1 C2 C4 Control Channels C3 Offset Time1 DB4 Offset Time1 DB1 Offset Time1 Data Channels DB3 Offset Time1 DB2 Time T1 T2 T3 T4 T5 No Buffer -> Contention occurs -> High Losses even in the light traffic load The longer path -> The higher probability of Loss -> Unfairness

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 Contending Burst Offset Time5 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

15. HBP Scheme Parameters

16. HBP Hp = 3 Ho = 3 Source5 Destination5 Contending will be dropped if HpContending / (HpContending + HoContending) < M M = 1/2 3/ (3+3) = 1/2 Contending Burst Contending Burst I5 I5 DB5 DB5 Scheduled Bursts I4 DB4 I1 DB1 I3 DB3 I2 DB2

17. HBP Hp = 3 Ho = 3 Source5 Destination5 I = (Hp * Wp ) - (Ho * Wo ) Wp = Wo = 1 I of the contending burst = 3-3 (Hp-Ho) = 0 Contending Burst Contending Burst DB5 DB5 I5= 0 Scheduled Bursts DB4 DB1 DB3 DB2

18. HBP Hp = 3 Ho = 3 Source5 Destination5 I4 = 1 I1= -1 Least I I3 = 3 I2 = 0 The contending burst wins the contention. Contending Burst Contending Burst DB5 DB5 I5= 0 Scheduled Bursts DB4 DB1 DB3 DB2 The contending burst can preempt the channel of the original burst if I5 – I1 >= T When T = 1 0-(-1) = 1

19. HBP C1 Offset Time1 DB5 DB1 T1 The corresponding switch cancels the original wavelength reservation for the original burst and instead allocates thewavelength for the contending burst. Contending Burst Offset Time5 DB5 C2 C4 C5 Control Channels C3 Offset Time1 DB4 Offset Time1 Data Channels DB3 Offset Time1 DB2 Time T2 T3 T4 T5

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

22. NSF Network

23. NSF Network

24. ARPA Network

25. ARPA Network

26. 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.