The document describes the design and implementation of a new high performance data transport protocol called UDT. UDT is implemented at the application layer over UDP to provide reliable, high-speed data transfer capabilities. It includes a new congestion control algorithm based on AIMD with decreasing increases that aims for efficiency, fairness and friendliness. Experimental results show UDT achieves high throughput and good fairness compared to TCP. The document also introduces a configurable framework called Composable UDT that allows new congestion control algorithms to be easily implemented and evaluated.

1. BREAKING THE DATA TRANSFER BOTTLENECK Yunhong GU [email_address] Laboratory for Advanced Computing National Center for Data Mining University of Illinois at Chicago October 10, 2005 udt.sourceforge.net UDT: A High Performance Data Transport Protocol

2. Outline INTRODUCTION PROTOCOL DESIGN & IMPLEMENTATION CONGESTION CONTROL PERFORMANCE EVALUATION COMPOSABLE UDT CONCLUSIONS

3. >> INTRODUCTION PROTOCOL DESIGN & IMPLEMENTATION CONGESTION CONTROL PERFORMANCE EVALUATION COMPOSABLE UDT CONCLUSIONS

7. TCP Throughput (Mb/s) Throughput (Mb/s) Packet Loss Round Trip Time (ms) 0.01% 0.05% 0.1% 0.1% 0.5% 1000 800 600 400 200 1 10 100 200 400 1000 800 600 400 200 LAN US-EU US-ASIA US

10. A New Protocol Throughput (Mb/s) Throughput (Mb/s) Packet Loss Round Trip Time (ms) 0.01% 0.05% 0.1% 0.1% 0.5% 1000 800 600 400 200 1 10 100 200 400 1000 800 600 400 200 LAN US-EU US-ASIA US

14. >> PROTOCOL DESIGN & IMPLEMENTATION INTRODUCTION CONGESTION CONTROL PERFORMANCE EVALUATION COMPOSABLE UDT CONCLUSIONS

16. UDT Overview UDP Socket API Applications TCP Socket API Applications Applications UDT UDT Socket

18. Protocol Architecture UDP Channel Sender Sender Receiver  Sender Receiver  UDP Seq. No TS Payload ACK Seq. No NAK Loss List A B

19. Software Architecture CC API UDP Channel Sender Receiver Sender's Buffer Receiver's Buffer Sender's Loss List Receiver's Loss List Listener

22. >> CONGESTION CONTROL INTRODUCTION PROTOCOL DESIGN & IMPLEMENTATION PERFORMANCE EVALUATION COMPOSABLE UDT CONCLUSIONS

25. AIMD with Decreasing Increases  ( x ) x AIMD (TCP NewReno) UDT HighSpeed TCP Scalable TCP

27. The Increase Formula: an Example Bandwidth ( B ) = 10 Gbps, Packet size = 1500 bytes 0.00067 <0.1 9999.9+ 0.001 (0.1, 1] [9999, 9999.9) 0.01 (1, 10] [9990, 9999) 0.1 (10, 100] [9900, 9990) 1 (100, 1000] [9000, 9900) 10 (1000, 10000] [0, 9000) Increment (pkts/SYN) B - x (Mbps) x (Mbps)

30. >> PERFORMANCE EVALUATION INTRODUCTION PROTOCOL DESIGN & IMPLEMENTATION CONGESTION CONTROL COMPOSABLE UDT CONCLUSIONS

33. Efficiency, Fairness, & Stability Flow 1 Flow 2 Flow 3 Flow 4 0 100 200 300 400 500 600 700 Time (sec) 206.220.241.16 206.220.241.15 206.220.241.14 206.220.241.13 145.146.98.81 145.146.98.80 145.146.98.79 145.146.98.78 1Gb/s bandwidth, 106 ms RTT, StarLight, Chicago SARA, Amsterdam

34. Efficiency, Fairness, & Stability 0.04 0.02 0.04 0.16 0.08 0.11 0.11 Stability 1 1 0.999 0.998 0.999 0.999 1 Fairness 885 904 918 830 923 912 902 Efficiency 197 Flow 4 307 202 302 Flow 3 452 310 216 308 446 Flow 2 885 452 301 215 313 466 902 Flow 1

36. >> COMPOSABLE UDT INTRODUCTION PROTOCOL DESIGN & IMPLEMENTATION CONGESTION CONTROL PERFORMANCE EVALUATION CONCLUSIONS

41. Simplicity & Expressiveness CCC Base Congestion Control Class CTCP TCP NewReno CGTP Group Transport Protocol CUDPBlast Reliable UDP Blast CFAST FAST TCP CVegas TCP Vegas CScalable Scalable TCP CHS HighSpeed TCP CBiC BiC TCP CWestwood TCP Westwood 28 73 / +132-6 11 / +192-29 8 / +27-1 11 / +192-29 27 / +145-2 37 / +351-2

43. >> CONCLUSIONS INTRODUCTION PROTOCOL DESIGN & IMPLEMENTATION CONGESTION CONTROL PERFORMANCE EVALUATION COMPOSABLE UDT