TCP improvements for Data Center Networks -- Tanmoy Das and Krishna M. Sivalingam

1. TCP improvements for Data Center Networks--Tanmoy Das and Krishna M. Sivalingam B99705021 李奕德

2. outline Abstract Intro ECN in DCTCP TDCTCP Performance evaluation conclusion

3. Abstract TCP does not fit in datacenter DCTCP may lower throughput due to small buffer size Improved version of DCTCP (called TDCTCP) Compare to existed algorithm (DCTCP, TCPNewReno) TDCTCP may have slightly higher delay but have much better throughput in general

4. outline Abstract Intro ECN in DCTCP TDCTCP Performance evaluation conclusion

5. introduction Data flow in datacenter: large data flowrequire high throughput small data flowrequire low latency Incastproblem

6. introduction TCP:provide : reliable, ordered byte streamdoes not provide: high throughput with “simultaneously low delay” Other similar solutions: DCTCP, TCPNewReno, TDCTCP Tested under OMNeT++ simulator

7. outline Abstract Intro ECN in DCTCP TDCTCP Performance evaluation conclusion

8. ECN in DCTCP ECN mechanism 2-bit used to describe current situation 00: Non ECN-Capable Transport — Non-ECT 10: ECN Capable Transport — ECT(0) 01: ECN Capable Transport — ECT(1) 11: Congestion Encountered — CE

9. outline Abstract Intro ECN in DCTCP TDCTCP Performance evaluation conclusion

10. TDCTCP A. Modification of Congestion Avoidance B. Resettingα after Delayed ACK timeout C. Dynamic Delayed ACK timeout calculation

11. TDCTCP-A part Modification of Congestion Avoidance α = fraction of marked packets in one congestion window Indicates current congestion level MSS = Maximum Segment Size Indicates the size of data that can be sent

12. TDCTCP-A part

13. TDCTCP-B part Resettingα after Delayed ACK timeout delayed ACK timeout: use in TCP to reduce ACKs send to the sender When ACK timeout occur: α is not updated Old α remain high and block increment of window size α is reset to 0 after every delayed ACK timeout

14. TDCTCP-B part Set α to 0 when this happen

15. TDCTCP-C part Dynamic Delayed ACK timeout calculation DCTCP: small buffer = small congestion window Congestion window reduce to 1, causing ACK timeouts

16. TDCTCP-C part Packet arrival follows an exponential distribution Packet loss probability in the network is small

17. TDCTCP Spend less time in ACK timeout Low variance in window size Use 10 flows to demonstrate

18. outline Abstract Intro ECN in DCTCP TDCTCP Performance evaluation conclusion

19. Performance evaluation Throughput Fairness Delay Queue length Variation in Delay Variation in Throughput

20. Performance evaluation Environment

21. Performance evaluation Throughput - single bottleneck, 1Gbps Better performance than DCTCP in general

22. Performance evaluation Throughput - single bottleneck, 10Gbps Better than DCTCP under smaller K Provide same throughput as TCPNewReno in early stages

23. Performance evaluation Throughput – multi-bottleneck, 10Gbps Better than DCTCP under smaller K Provide same throughput as TCPNewReno in early stages

24. Performance evaluation Fairness- single bottleneck, measure in JFI better fairness in every scenario

25. Performance evaluation Fairness- multi-bottleneck, measure in JFI

26. Performance evaluation Delay- single bottleneck , 10 Gbps TCPNewReno is good except high delay

27. Performance evaluation Delay- multi-bottleneck , 10 Gbps

28. Performance evaluation Queue length TDCTCP is slightly longer than DCTCP

29. Performance evaluation Variation in Delay

30. Performance evaluation Variation in throughput

31. outline Abstract Intro ECN in DCTCP TDCTCP Performance evaluation conclusion

32. conclusion Modified DCTCP => TDCTCP 15% higher throughput than DCTCP improved fairness compare to DCTCP provides more stable throughput queue length is slightly more than that of DCTCP at 10Gbps delay is slightly higher than that of DCTCP

33. The endthank you for your attention Any questions??