Modeling The Performance of FAST TCP over High-Speed and Wireless Networks by

1. Modeling The Performance of FAST TCP over High-Speed and Wireless Networks by Dasari, Ramesh Chandra Parameswaran, Subramanian

2. CONTENTS • Introduction • What’s Wrong with TCP? • Fast TCP – The Promise • Delay-based Congestion Control • Fast TCP over High-Speed Networks • Implementation • Fast TCP over Wireless • Implementation • Results • Conclusion • References

3. INTRODUCTION • Internet growing in size everyday • Applications demand transfer of huge files • Congestion control algorithm needs improvisation • FAST TCP gives a much better throughput and utilization when compared to TCP

4. What’s Wrong with TCP? • TCP has performed remarkably well till now • Problem with TCP over large bandwidth-delay product networks • Packet Level: Linear increase of 1pkt/RTT is too slow. • Packet Level: Oscillations are unavoidable • Flow Level: hard to achieve small equilibrium loss probability • Flow Level: Unstable dynamics • Oscillations at packet and flow level overcome by equation-based control • Wireless links have high BER  data is easily corrupted. This causes retransmission timer to expire • In both cases TCP enters slow-start phase and transmission window drops to one segment

5. FASTTCP – ThePROMISE • High-Speed, High Link Utilization and Throughput • Download rates in the order of 100 – 500 Mbps • All this using current infrastructure • Equation-based, hence avoids oscillations • Stable flow dynamics • Uses queuing delay rather than loss probability

7. TCP Source TCP Destination DELAY-BASEDCONGESTIONCONTROL Forward Buffer ACK DELAY ACK Buffer • Loss probability 1 bit congestion information • Queuing Delay RTT provides multibit information • Hence estimation is easier • Basic idea of Fast TCP is to delay the ACKs being transferred from the TCP destination towards the TCP source.

8. Fast TCP over High-Speed Networks • Delay ACKS from destination to source • Fast TCP controls ACK output rate • Instead of discarding packets, the congested node delays ACKS • Hence output rate decreases • Delay in ACKS slows down transmission rate

9. Implementation Transmission Rate = 15Mbps ;Window Size = 50000; Maximum Segment Size = 512 bytes; Queue Buffer Capacity = 400000; Delays of 1ms each for the blocks Delay #5 and Delay #7. Delay #8 (Ack Delay) has a delay of 0.13s; Ack Timer – 0.01s Application Delay = 0.01s; Forward Buffer for Fast TCP node = 200000; Ack Buffer for Fast TCP = 200000

10. Fast TCP over Wireless • Current TCP attributes all losses to buffer overflows Packet Losses in Wireless Networks Buffer Overflows Wireless Environment like handoffs, interference, fading • When TCP encounters losses due to the wireless environment it gets confused

11. IMPLEMENTATION The forwarding rate of the TCP source and destination is 106 pkts/s, buffers for both directions are 2Mbit, TCP initial RTO is 1s and TCP maximum segment size is 512 bytes. The routers have IP forwarding rate 15000 pkts/s, buffers of 2Mbits and a congestion notification threshold of 400000 bits. The links between routers and TCP hosts is 150Mbps while the wireless link between the routers is 30Mbits/s. There is a propagation delay of from the TCP source to router 1 and from router 2 to the TCP destination, which is 1 ms while the propagation delay over the wireless link from Router 1 to Router 2 is 150 ms.

12. RESULTS FAST TCP’s link utilization exceeds TCP’s by 25%

13. FAST TCP vs TCP: 21% better throughput

14. CONCLUSION • Fast TCP achieves a better link utilization and throughput than TCP with negligible change to infrastructure • Due to Software limitations, we could not implement the Fast TCP node into the router in a wireless network • In due time users can have High-speed Internet access with almost no congestion

15. REFERENCES [1]Wang Qian, Wu Jing, Cheng Shiduan, Ma Jian, Differentiated service Fast-TCP Policy for Flow Control and Resource Management. Communication Technology Proceedings, 2000. WCC - ICCT 2000. International Conference on, Volume: 2, 21-25 Aug. 2000. [2] Cheng Jin, Wei, D.X., Low, S.H, Fast TCP: Motivation, Architecture, Algorithms, Performance; INFOCOM 2004. Twenty-third AnnualJoint Conference of the IEEE Computer and Communications Societies, Volume: 4, 7-11 March 2004. [3] Fei Peng, Shiduan Cheng, Jian Ma, Performance Analysis Of Fast-TCP Mechanism For Networks With High Bandwidth-Delay Products; Communication Technology Proceedings, 2000. WCC - ICCT 2000. International Conference on, Volume: 1, 21-25 Aug. 2000. [4] Jing Wu, Peng Zhang, Tao Du, Jian Ma, Shiduan Cheng, Improving TCP Performance In ATM Network By The Fast TCP Flow Control. Communication Technology Proceedings, 1998. ICCT '98. 1998 International Conference on, Volume: vol.2, 22-24 Oct. 1998. [5] Qian Wang, Jing Wu, Shiduan Cheng, Jian Ma, Fast TCP Flow Control With Differentiated Services. Communications, 1999. APCC/OECC '99. Fifth Asia-Pacific Conference on ... and Fourth Optoelectronics and Communications Conference, Volume: 1, 18-22 Oct. 1999. [6] www.mldesigner.com/