1. A Two-Phase TCP Congestion Control for Reducing Bias over Heterogeneous Networks Jongmin Lee, Hojung Cha, Rhan Ha Yonsei University, Korea Information Networking, Convergence in Broadband and Mobile Networking, International Conference, ICOIN 2005, Jeju Island, Korea, Jan 31- Feb 2, 2005

2. Outline a sender side TCP congestion control scheme reduce bias for different round trip time in wired and wireless networks

3. Outline Introduction Algorithms –Bandwidth measurement –Determining transfer rate –congestion control Experimental results Conclusion

4. Introduction Problem of Reno TCP –slow increase of transfer rate after congestion –significant in high speed networks with long delays, and wireless networks

5. TCP-TP Two phase –fair convergence phase –congestion avoidance phase non-bulk data transfer –AIMD bulk data transfer –adjust transfer rate adaptively considering both current transfer rate and estimated bandwidth

6. Bandwidth measurement

7. Determining Transfer Rate

8. regardless RTT new flow has large diff

9. Determining Transfer Rate = number of ACK in one RTT: number of packets to send after receiving ACK:

10. Congestion Control

11. Experiments Linux kernel 2.6.7 NIST

12. Experiments

15. Conclusions TCP-TP –fair convergence phase: based on BDP and cwnd –congestion avoidance phase: similar to traditional TCP in order to share fairly Advantages: –reduce bias to different RTT –faster transfer rate increase, good to high speed networks, new flow, wireless –TCP-friendly

16. Appendix