1. WebTP Meeting (10/18/1999) Link Sharing Principles Class Based Queueing (CBQ) S. Floyd and V. Jacobson - ToN 1995

2. Goals Link Sharing: –Distribute bandwidth according to some hierarchy

3. Goals Link Sharing: –Distribute bandwidth according to some hierarchy CBQ: A unified framework for supporting – Link Sharing – Real-time (delay sensitive) services

4. Link Sharing between Traffic Classes

5. Link Sharing Leaf Class Interior Class

6. Link Sharing Level 1 Level 2 Level 3

7. Link Sharing between Users

9. Link Weights Allocation Static Dynamic –network condition –user preferences –adding/removing connections

10. Link Sharing Goal Over appropriate time-intervals, each interior or leaf class should receive its allocated bandwidth (given sufficient demand)

11. Link Sharing between Users

12. Link Sharing between Traffic Classes

13. CBQ Fundamentals Scheduling –General scheduler –Link sharing scheduler

14. CBQ Fundamentals Scheduling –General scheduler –Link sharing scheduler Classes –Unregulated –Regulated

15. CBQ Fundamentals Scheduling –General scheduler –Link sharing scheduler Classes –Unregulated –Regulated Bandwidth Estimator –Exponential weighted moving average

16. Classes - Definitions Bandwidth Utilization –Overlimit –Underlimit –At-limit

17. Classes - Definitions Bandwidth Utilization –Overlimit –Underlimit –At-limit Satisfaction –Unsatisfied: Underlimit + persistent backlog –Satisfied

18. Link Sharing - Guidelines A class stays unregulated if 1. It is not overlimit

19. Link Sharing - Guidelines A class stays unregulated if 1. It is not overlimit, OR 2. It has a not-overlimit ancestor at level j, and there are no unsatisfied classes in the link- sharing structure at levels lower than j.

20. Link Sharing - Guidelines A class stays unregulated if 1. It is not overlimit, OR 2. It has a not-overlimit ancestor at level j, and there are no unsatisfied classes in the link- sharing structure at levels lower than j. Otherwise it should be regulated

21. Link Sharing - Guidelines A class stays unregulated if 1. It is not overlimit, OR 2. It has a not-overlimit ancestor at level j, and there are no unsatisfied classes in the link- sharing structure at levels lower than j. Otherwise it should be regulated Remark: The root is always not-overlimit

22. Examples

23. Example 1 Under Over

24. Example 2 Under Over

25. Example 2 Backlog

26. Example 2 Unsatisfied

27. Example 2 Regulated Unsatisfied

28. Example 3 Unsatisfied Overlimit + Backlog Regulated

29. CBQ - Pros Bandwidth protection Hierarchy Support of priorities for delay-sensitive services flexibility

30. CBQ - Cons No deterministic/statistical guarantees on performance measure (delay, throughput) Many tunable parameters with unknown effects

31. CBQ and WebTP Allow sharing of multiple connections with different requirements within a pipe Allow sharing between multiple users or protocols (FAT pipes) Open questions: –Traffic classification, admission control –Variable-rate server –interaction with the ADU scheduler