1. An Introduction to UDT Internet2 Spring Meeting Yunhong Gu gu@lac.uic.edugu@lac.uic.edu Robert L. Grossman (Advisor) National Center for Data Mining University of Illinois at Chicago

2. What's UDT? UDT: UDP-based Data Transfer Protocol Application level, end-to-end, unicast, reliable, connection-oriented, streaming data transport protocol. Successor of SABUL Open source C++ Implementation

3. Layered Architecture UDP OS Socket Interface UDT UDT Socket API Applications User Space Kernel Memory Copy Avoidance

4. Flow/Congestion Control AIMD: Additive Increases Multiplicative Decreases Increase Parameter  Related to available bandwidth  Bandwidth estimation: automatic parameter tuning Decrease Factor  Randomized decrease factor: alleviate loss synchronization problem

5. Performance Characteristics Efficiency  Approximately constant time to probe 90% of available bandwidth Fairness  Intra-protocol fairness (max-min)  RTT independent  TCP friendly

6. Configurable Congestion Control UDP OS Socket Interface UDT UDT Socket API Applications User Space Kernel CC

7. How to Use UDT? Linux  Ported to Windows, UNIX, BSD, and OS X C++ API  socket-like API Transport Middleware  XIO UDT Driver C API  No changes for existing applications, just recompilation and link  Limitation: no "fork" Java and Python wrapper

8. Non-objectives and limitations Not a replacement to TCP  For bulk data transfer over high-speed wide area networks, where TCP does not work well  UDT is designed to co-exist with TCP Built-in control algorithm is not suitable for applications requires real-time, messaging, lossy, or smooth data traffic. Not suitable for high concurrency (a large number of flows sharing the network)

9. http://udt.sf.net UDT Source Code Stable release (v2.0) CVS (most recent update and bug fixes) Technical papers Online documentation

10. Questions? http://udt.sf.net http://www.ncdm.uic.edu gu@lac.uic.edu http://udt.sf.net http://www.ncdm.uic.edu gu@lac.uic.edu