1. Network and Protocol Mechanisms: How well do they collaborate? Ageliki Tsioliaridou

2. What we investigate Transport Protocols come at various versions - some aggressive some conservative Network mechanisms differ in sophistication regarding the scheduling, forwarding and dropping policy

3. We claim that Evaluation of a new mechanism cannot be investigated alone; that is, one has to study its impact on the different mechanisms. A protocol may lack the sophistication needed to exploit the potential of a new network mechanism, and vice versa the chicken or the egg

4. More specifically We select two widely used network mechanisms (DT and RED); we also introduce a new mechanism, namely Fr-RED; and we discuss the potential of another mechanism which we will develop soon We monitor the interaction of these mechanisms with the congestion control mechanisms of Tahoe, Reno, NewReno and Vegas

5. 1 st scenario Many flows compete for low bandwidth. The contention level is high. Congestion event is persistent 2 nd scenario A small number of flows occupy the transmission channel. The contention level is low. Congestion event is transient 3 rd scenario Some flows co-exist in the communication channel and suddenly some other flows enter the link 4 th scenario Some flows co-exist in the communication channel and suddenly some of them finish their task and leave the channel

6. Experiments Topology: dumbbell

7. 1 st scenario Topology:dumbbell bw_1=0.1Mbps, bw_2=1Mbps, bw_3=0.1Mbps Remarks that have to be highlighted: 1.If the protocol is Vegas or Tahoe, the combination with drop give us better results in throughput 2.If the protocol is Reno or Newreno, the combination with red give us better results not only in goodput but also in throughput 3.When the router’s algorithm is drop, the performance of Vegas in goodput is higher than the other three

8. TCP Tahoe goodput throughput

9. TCP Vegas goodput throughput

10. TCP Reno goodput throughput

11. TCP NewReno goodput throughput

12. DropTail

13. 2 nd scenario Topology:dumbbell bw_1=1Mbps, bw_2=50Mbps, bw_3=10Mbps Remarks that have to be highlighted: 1.If the protocol is Tahoe the combination with drop give us better results 2.If the transport protocol is Vegas the value of goodput doesn’t get influence from the router’s algorithm, and it is higher than the value of other three protocols.

14. TCP Tahoe goodput throughput

15. TCP Vegas goodput throughput

16. RED

17. 3 nd scenario Topology:dumbbell bw_1=1Mbps, bw_2=50Mbps, bw_3=10Mbps Remarks that have to be highlighted: The combination of Vegas and Drop Tail algorithm gives us the worst value in fairness When of the transport protocol is Tahoe, the Drop Tail algorithm performs better in goodput If the transport protocol is Vegas it gives the best value in goodput

18. Fairness

19. TCP Tahoe goodput

20. goodput throughput TCP Vegas

21. 4 th scenario Topology:dumbbell bw_1=1Mbps, bw_2=50Mbps, bw_3=10Mbps Remarks that have to be highlighted: When the transport protocol is Reno, the Drop algorithm results better in fairness When of the transport protocol is Tahoe, the drop algorithm perfumes better in goodput If the transport protocol is Vegas the value of goodput is higher than the value of other three protocols.

22. TCP Reno fairness

23. TCP Tahoe goodput

24. goodput throughput

25. Random Early Drop (RED) A router that implements RED uses two threshold values to mark positions in the queue: T min and T max AvgLen T min T max 2* T max

26. A drop event is characterize either as FORCED drop nor as UNFORCED drop DROP LOGIC 1.If avg > 2* maxthresh, this is a FORCED drop 2.If T min < avg < 2*maxthresh, this may be an UNFORCED drop. The drop probability changes from 0 to max_p as the avg varies from T min to T max and from max_p to 1 as the avg varies from T max to twice T max (max_p=1/linterm) 3.If (q+1) > hard q limit, this is a FORCED drop

27. RED drop principle: FORCED drop The victim is either the arriving packet (default) or the front packet of the queue or any packet of packet (random) UNFORCED drop The victim is the arriving packet fr-RED drop principle : FORCED drop The victim is the arriving packet UNFORCED drop The victim is the front packet of the queue

28. Our goal is: To indicate senders faster that the congestion is going to happen The TCP congestion mechanism of senders will be triggered faster

29. Experiments Topology: dumbbell scenario bw_1=bw_2=bw_3=1Mbps

30. TCP Tahoe Buffer_size (bs):100 Link_delay:7ms Tmax:3*bs/4=75 Tmin:Tmax/3=25

31. TCP Tahoe Buffer_size (bs):100 Buffer_size (bs):200

32. The concept of a new network mechanism: When congestion is going to happen rearrange the order of the packets at the queue The concept of a new congestion control mechanism: The sender should adjust its rate, depending on the reordering of the incoming packets at the receiver.

33. Future work Evaluation of fr-red at high-speed networks Implementation of the new concept of congestion avoidance mechanism