1. Graded Channel Reservation with Path Switching in Ultra High Capacity Networks Reuven Cohen, Niloofar Fazlollahi, David Starobinski ECE Dept., Boston University Gridnets Workshop 2006 San Jose, CA

2. Acknowledgements US Department of Energy Dr. N. Rao, ORNL

3. Outlines Advanced Channel Reservation Contributions Models and Algorithms Related work Variants Performance Evaluation Conclusion

4. Motivation Grid computation : Large Hadron Collider (LHC) at CERN Exabytes (10 18 bytes) → need for new protocol to support huge file transfers http://lhc.web.cern.ch/lhc/LHC_Experiments.htm

5. Advanced Channel Reservation Emergence of new protocol stack complements TCP/IP Properties: 1 - Users request resources for connection in advance (bandwidth/duration, file size) 2 – Dedicated resources allocated by a scheduler (centralized or replicated) 3 – Implemented directly on top of layer 2

6. UltraScience Net http://www.csm.ornl.gov/ultranet/

7. ACR Challenges Scheduling Routing Goal: maximum utilization of resources EarliestShortest A B

8. Graded Channel Reservation (GCR) Contributions:  path grading multi-criteria path optimization (shortest, earliest)  path switching connection can switch between paths  Complexity analysis (small polynomial)  Performance evaluation

9. Model Model: G (V,E) V: {A, B, C} E: {AB, AC, BC} requests: response: (time,path) Objective: Highest grade path A B C Source Destination Bandwidth Duration

10. Grading Example Primary grading criterion: earliest path Secondary grading criterion: Shortest Widest

11. Example (Cont.) Thm: GCR always returns the earliest time at which a path satisfying requested bandwidth B and duration T can be established between nodes s and d. Return path with highest grade (e.g., earliest-shortest)

12. GCR Algorithm:  Time slots: connection set up/ tear down  Steady state residual graph  Graph intersection  yes - highest grade path no – start from next slot  Reserve bandwidths BFS path search

13. Related Work Most closely related: Guerin & Orda, INFOCOM, 2000 Rao, Wing, Carter & Wu, IEEE ComSoc Mag., 2005 Focus on single criterion optimization No path switching Limited performance evaluation

14. Advantage of path switching A C Slot 1: [1,1:30] Slot 3: [4,8] Slot 2: [1:30,4] Request: (A,C) at time 2:00 pm, duration = 4 hours B A C B A C B A C B Slot 3: [2,4]Slot 2: [1:30,2] A C B Slot 5: [6,8]Slot 4: [4,6]

15. Variants to GCR GCR switch Switch to best grade path available at each slot

16. Reducing Path Switches GCR minimum Thm: GCR minimum returns the earliest path and minimizes number of path switches. GCR limitx Heuristic: limits up to x switches

17. Simulation measures & parameters Performance measures: 1- average delay 2- saturation throughput Requests: (s,d,B,T) Parameters:  uniform source  uniform or hot-spot destination  uniform or 80/20 bandwidth  exponential or heavy-tailed connection length

18. Topologies

19. Performance Evaluations

21. Conclusion Framework: grading & switching 1 st and 2 nd path optimization important Path switching widely improves performance

22. Future Work Time window: simulating blocking probability Cost of switching