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Optimizing UDP-based Protocol Implementations

Optimizing UDP-based Protocol Implementations. Yunhong Gu and Robert L. Grossman Presenter: Michal Sabala. National Center for Data Mining. Outline. UDP Performance Characteristics and Optimizations Composable UDT: A Framework for UDP-based Protocol Implementations.

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Optimizing UDP-based Protocol Implementations

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  1. Optimizing UDP-based Protocol Implementations Yunhong Gu and Robert L. Grossman Presenter: Michal Sabala National Center for Data Mining

  2. Outline • UDP Performance Characteristics and Optimizations • Composable UDT: A Framework for UDP-based Protocol Implementations

  3. Part I. UDP Performance Characteristics and Optimization Techniques

  4. Introduction • UDP-based Protocol is needed • As short-term solution to the lack of effective kernel space transport protocols for high bandwidth-delay product networks • As application specific data transfer library, e.g., Multimedia data transfer • It is not an easy task to impalement a new UDP-based protocol from scratch • And may be not necessary!

  5. UDP Performance • Sending and receiving buffer size • Packet size • IO mode • Scattering/gathering (writev/readv) • Memory copy avoidance (e.g., overlapped IO of Windows Socket2) • To reach same data transfer rate, UDP needs slightly less CPU time than TCP, and cause slightly less end system delay

  6. UDP Performance: Impact of Buffer Size

  7. UDP Performance: Impact of Packet Size Throughput CPU Util.

  8. UDP-based Protocol Performance • Additional overhead • Additional memory copy • Additional packet processing • Additional context switches

  9. Optimization Guidelines • Avoid additional memory copy • Reduce the number of packets • Control packets, esp. acknowledgements • Reduce overall processing time • Simpler mechanism is better • Avoid burst in processing time • CPU may be too busy to process incoming packets

  10. Optimization Guidelines • Memory copy avoidance • UDP IO • API semantics • Acknowledgements • Timer-based Acknowledging • Light ACK • Loss processing • Timing, rate control, and self-clocking

  11. Optimization Guidelines • Disk IO • sendfile/recvfile • Threading • Synchronization cost • Code Optimization • sending/receiving loop • Profiling

  12. Part II. Composable UDT: A Framework for UDP-based Protocol Implementations

  13. Composable UDT • Based on the UDT (UDP-based Data Transfer library) implementation • Integrated those optimization techniques described in this paper

  14. Objectives • Rapid development of UDP-based transport protocols and application specific data transfer libraries • Easy evaluation of new congestion control algorithms • Non-objectives • Replace kernel space protocol implementations • User-level TCP implementation

  15. Current Status • UDT/CCC: Configurable congestion control • In future • Data reliability configuration • Message boundary support

  16. Configurable Congestion Control • Packet sending control • Rate-based, window-based, hybrid • Redefinition of control event handlers • Loss, ACK, Time Out, etc. • Access to internal protocol parameters • RTT, RTO, Loss Rate, etc. • User customized packet formats

  17. Implementation • C++ class inheritance • CCC: base class for control event handing • Callbacks • Performance monitoring • Internal protocol parameters • Performance statistics

  18. Implementation

  19. Example: Simplified TCP

  20. Configurable Congestion Control

  21. Future Work • Continue to improve the UDT/CCC library • More experimental evaluation work of the UDT/CCC library • Compare k-TCP and u-TCP in more network environments • Implement more TCP variants • More pre-implemented congestion control algorithms

  22. Conclusion • UDP-based protocol is one of the solutions to bulk data transfer in high BDP networks • Some optimization principles and techniques are discussed in this paper • We further propose a composable framework in order to make it much easier to implement UDP-based protocols

  23. Thank you! For more information, please visit UDT Project: http://udt.sf.net NCDM: http://www.ncdm.uic.edu

  24. Backup Slides

  25. UDP Performance: Experiment Setup

  26. UDP Performance: CPU Utilization

  27. UDP Performance: End System Delay

  28. UDT Profiling: Modules

  29. UDT Profiling: Functionalities

  30. CPU Utilization: K-TCP vs U-TCP

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