1. Milano 25/2/20031 Bandwidth Estimation for TCP Sources and its Application Prepared for QoS IP 2003 R. G. Garroppo, S.Giordano, M. Pagano, G. Procissi, R. Secchi Department of Information Engineering University of Pisa

2. Milano 25/2/20032 Introduction TCP is the most used reliable and connection oriented transport service TCP is called to operate in different network environment TCP Westwood proposal enhances TCP performance and fairness, expecially in mixed wired/wireless environment

3. Milano 25/2/20033 Outline Bandwith Estimation –Algorithm –Numerical validation –Accuracy in estimation Application to TCP –Performance Evaluation –Fairness and Friendliness –Conclusion

4. Milano 25/2/20034 Bandwidth Estimation Technique BWE is computed at the sender side by processing ACK time series Estimators design assumes a simple network model (single bottleneck approximation) Available Bandwidth is computed by comparing packet inter-departure time of packet and from inter-arrival time of ACKs

5. Milano 25/2/20035 Bandwidth Estimator Scheme If queueing occurs at the bottleneck L packet size µ bottleneck capacity λ cross traffic rate

6. Milano 25/2/20036 Linear-Regression technique 1.Collect a sample of RTT and ACK inter-arrival time, only if: 2.Perform a linear over sample pairs: 3.Computes bandwidth estimation, by performing linear- regression:

7. Milano 25/2/20037 Numerical Validation Loss free channel Lossy channel Bandwidth Estimation UDP Source TCP Source 10Mbs, 10ms 2Mbs, 40ms NS-2 Simulation Topology Lossy link

8. Milano 25/2/20038 Numerical Validation (a) Lossfree channel Bandwidth Estimation (b) Lossy channel Disturb Traffic flowing in the opposite direction

9. Milano 25/2/20039 Bandwidth Estimation Accuracy BWE Accuracy (with concurrent CBR/UDP Traffic) Bandwidth Estimation

10. Milano 25/2/200310 Algorithm flow chart ssthresh := pipesize 3 DupACKs Received cwnd > ssthresh yes cwnd := ssthresh no Timeout expires cwnd := 1 ssthresh := pipesize ssthresh < 2 yes ssthresh := 2 no Application to TCP

11. Milano 25/2/200311 Topology of Simulation NS-2 topology Modified TCP Source Application to TCP

12. Milano 25/2/200312 GoodPut Comparison (a) UDP rate: 100Kbps (b) UDP rate: 500Kbps Application to TCP TCP Througput vs Loss Probability on lossy link

13. Milano 25/2/200313 Completion Time Comparison Average Completion Time ( 60 packets long flows ) Application to TCP

14. Milano 25/2/200314 Fairness and Friendliness concepts Fairness: identical connection sharing a common resource achieve the same performance Friedliness: A friendly protocol doesnt hurt standard protocol more than a homogeneous protocol

15. Milano 25/2/200315 Modified NewReno-Fairness (a) Lossfree channel (b) Lossy channel Goodput achieved by a couple of connections sharing a common link. Different CBR/UDP disturb traffic rate are considered. Application to TCP

16. Milano 25/2/200316 Modified NewReno Friendliness Modified NewReno Friendliness towards NewReno (a) Lossfree channel (b) Lossy channel Application to TCP

17. Milano 25/2/200317 Modified NewReno Friendliness NewReno vs. Mod. NewReno in lossy channel Application to TCP

18. Milano 25/2/200318 Conclusion We propose an end-to-end bandwidth estimation technique for TCP connection. Extensive simulation validate the effectiveness of the algorithm under various network conditions. The algorithm has been applied to TCP congestion control mechanism. The new protocol performance is assessed through simulations, showing clear improvement and compatibility towards NewReno.