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Network Available Bandwidth Measurements

Network Available Bandwidth Measurements. XiaoLong HE. Outline of the Talk. Problems Related Work Traffic Design Our Approach (SimProbe) Analysis of Simulation Results SMRT Implementation Lessons Learned Future Work. Why measurement?. Measurement is critical to network control.

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Network Available Bandwidth Measurements

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  1. Network Available Bandwidth Measurements XiaoLong HE

  2. Outline of the Talk • Problems • Related Work • Traffic Design • Our Approach (SimProbe) • Analysis of Simulation Results • SMRT Implementation • Lessons Learned • Future Work XiaoLong He Network Available Bandwidth Measurements

  3. Why measurement? • Measurement is critical to network control. • Measurement for selecting server/ISP • Measurement for verifying network configuration • Measurement for designing real-time applications • Measurement for load balancing in WAN • Measurement for accounting XiaoLong He Network Available Bandwidth Measurements

  4. Taxonomy of Internet Network Measurement Approaches • Sender-based vs. Receiver-based • Passive Watch vs. Active Probe • Layer of Protocol used XiaoLong He Network Available Bandwidth Measurements

  5. Measurement Problems • Route Fluttering • Packet Loss • Out of Order packet delivery • Clocks Synchronization • Routers reject ICMP due to denial of series attacks. XiaoLong He Network Available Bandwidth Measurements

  6. Bottleneck Bandwidth • Bottleneck bandwidth:the maximal rate at which data can be sent along a connection, determined by the slowest element in the entire chain. XiaoLong He Network Available Bandwidth Measurements

  7. Available Bandwidth • Available Bandwidth:how fast can the data in fact be transmitted over the connection. • [PacketSize/(PacketSize+CompetitorPacketSize)] * Bottleneck Bandwidth XiaoLong He Network Available Bandwidth Measurements

  8. Related Works • Bprobe/Cprobe - Robert L. Carter and Mark E. Crovella, Boston University, 1996 • Ping - M. Muuss, U.S.Army Ballistic Research Laboratory, 1983 • Traceroute - Van Jacobson, Berkeley, Univeristy of California, 1997 • Treno - M. Mathis and J. Mahdavi, Proceedings of INET’96, Montreal, 1996 XiaoLong He Network Available Bandwidth Measurements

  9. Bprobe/Cprobe • Bottleneck Bandwidth = (PacketSize/Time) • Available Bandwidth = (S2+…+Sn)/(Tn-T1) XiaoLong He Network Available Bandwidth Measurements

  10. SimProbe Simulator • To carry the thesis out, we build a Java-based discrete event simulator. • Swing, Java2D and AWT packets for GUI design • Thread for comparing different probing methods • Port it to Unix (without GUI) for long time simulation XiaoLong He Network Available Bandwidth Measurements

  11. How traffic is generated in SimProbe Simulator XiaoLong He Network Available Bandwidth Measurements

  12. Traffic Patterns supported by SimProbe • Flat/Static • Slope • Web (modifed code by Arthur Blais) • Time between requests: Pareto Distribution • Number of embedded references: Pareto Distribution • Time between references: Weibull Distribution • File Size: Body (Lognormal Distribution) Tail (Pareto Distribution) XiaoLong He Network Available Bandwidth Measurements

  13. Network Topology Used in This Simulation Study XiaoLong He Network Available Bandwidth Measurements

  14. Our Approaches • Sending as few packets as possible. Using round trip time measurements for network available bandwidth. • Trip Time Measurement Formula:TripTime*MeasuredAvailableBandwidth = MinimalTripTime*MaximalAvailableBandwidth • Round Trip Time Measurement • SMRT • MMRT • Unidirectional Trip Time Measurement • SMUT • MMUT • Time Gap between packets • ACB (Adaptive Cprobe) XiaoLong He Network Available Bandwidth Measurements

  15. SMRT(Single Msg Round Trip Time Measurement) • Using multiple packets to find minimum of the round trip time of a connection • Using Bprobe to get the maximal available bandwidth of a connection • Sending single probing packet • Using round trip time to estimate the available bandwidth of the connection XiaoLong He Network Available Bandwidth Measurements

  16. MMRT • Use Bprobe to get the maximal available bandwidth of a connection • Using multiple packets to find minimum of the round trip time of a connection • Sending multiple packets • Round trip time for estimating ABW XiaoLong He Network Available Bandwidth Measurements

  17. SMUT • Use Bprobe to get the maximal available bandwidth of a connection • Using multiple packets to find minimum of the unidirectional trip time of a connection • Sending single probing packet • Using unidirectional trip time for estimating available bandwidth XiaoLong He Network Available Bandwidth Measurements

  18. MMUT • Use Bprobe to get the maximal available bandwidth of a connection • Using multiple packets to find minimum of the unidirectional trip time of a connection • Sending multiple probing packets • Using unidirectional trip time for estimating available bandwidth XiaoLong He Network Available Bandwidth Measurements

  19. Simulation result analysis • Difference Metric:|AvailableBandwidth - MeasuredAvailableBandwidth| AvailableBandwidth • AvailableBandwidth = [PacketSize/(PacketSize+QueuingSize)]* Bottleneck Bandwidth • MeasuredAvailableBandwidth = (MinimalTripTime*MaximalAvailableBandwidth)/ TripTime • DelayTime:TripTime - MinimalTripTime XiaoLong He Network Available Bandwidth Measurements

  20. XiaoLong He Network Available Bandwidth Measurements

  21. XiaoLong He Network Available Bandwidth Measurements

  22. SMRT Random Characteristics • Problem: Dependent on the arrival time of probing packet on bottleneck link • Three Scenarios: 1) no queuing time, yields bottleneck available bandwidth. 2) yields the lower bound of bottleneck available bandwidth 3) yields average bottleneck available bandwidth XiaoLong He Network Available Bandwidth Measurements

  23. Impact of Packet Size on SMRT • DelayTime rises when probing packets size increases. • Smaller packet size gets worse results • RoundTripTime = MinimalRoundTripTime + DelayTime • Examples: • T1 / (T1+T) • T2 / (T2+T) XiaoLong He Network Available Bandwidth Measurements

  24. Impact of Link Length on SMRT • The result accuracy is worse with the length increasing • Delay Time dominates RoundTrip Time at shorter link length • Propagation time dominates RoundTrip Time at longer link length XiaoLong He Network Available Bandwidth Measurements

  25. Impact of Router Speed on SMRT • No apparent difference for 1GBps or 10GBps • Router Speed affects the time gap between packets • Slow router speed enlarges the time gap between packets • Router Speed must be faster than link speed XiaoLong He Network Available Bandwidth Measurements

  26. Impact of Bottleneck Link Bandwidth on SMRT • SMRT results follow the available bandwidth trend • SMRT performance is similar to the performance trend by SMRT performance with 10MBps bottleneck link bandwidth XiaoLong He Network Available Bandwidth Measurements

  27. MMRT • Try to alleviate the random characteristic of SMRT • Small time gap between probing packets may experience big traffic difference in Slope traffic pattern • Obvious improvement on SMRT performance in web traffic XiaoLong He Network Available Bandwidth Measurements

  28. SMUT • Measure the available bandwidth on unidirectional route. • SMUT has the same random characteristics as SMRT. XiaoLong He Network Available Bandwidth Measurements

  29. MMUT • Try to alleviate the random characteristic of SMUT • Small time gap between probing packets may experience big traffic difference with slope traffic pattern • MMUT has Better performance than SMUT with web traffic pattern XiaoLong He Network Available Bandwidth Measurements

  30. ACB • Using the last measured available bandwidth • Send two packets once a time • Reprobing in Cprobe if time gap between packets is inside of a range • Not better than Cprobe XiaoLong He Network Available Bandwidth Measurements

  31. Summary of Simulation Analysis XiaoLong He Network Available Bandwidth Measurements

  32. Implementation of SMRT • SMRT is implemented in C • Maintain a host file, which specifies the list of sites to be probed • Bprobe is used to measure the largest bottleneck available bandwidth • Ping is used to measure the smallest round trip time of a connection • Using Bprobe and Ping to collect the history information for each host in the file, at offpeak and over a long period • Probed host must be contained in the host file • Round trip time of the probing message is used to measure the instant available bandwidth XiaoLong He Network Available Bandwidth Measurements

  33. Implementation results of SMRT • We probed a list of mirror sites for popular software packages such as perl, linux and netscape XiaoLong He Network Available Bandwidth Measurements

  34. Implementation results of SMRT • Orst is good choice for us to download software XiaoLong He Network Available Bandwidth Measurements

  35. Implementation results of SMRT • Orst gives us relative short round trip time XiaoLong He Network Available Bandwidth Measurements

  36. Lessons Learned • Impact of router speed on traffic generation • Problem: When router speed is lower than the bottleneck link speed, we can not get expected traffic? • Solution: Make sure the router speed in our connection is greater than the bottleneck link speed, especially for the large bottleneck link bandwidth XiaoLong He Network Available Bandwidth Measurements

  37. Lessons Learned (Cont) • Cprobe Limitations • Probing returned packets interfere with later probing packets • Queuing time is not the only results from connection competition • Examined factors: • Router Speed • Hop Number • Message Size • Message Number XiaoLong He Network Available Bandwidth Measurements

  38. XiaoLong He Network Available Bandwidth Measurements

  39. XiaoLong He Network Available Bandwidth Measurements

  40. Lessons Learned (Cont) • OOP design in Java • Problem: Chart can not be updated when we call the chart in a thread directly. • Solution: Using SwingUtilities.invokeLater Class • Double data type precision problem • Problem: The round trip time with traffic pattern is even shorter than the time without any traffic • Reason: machine double type data has a precision problem in representing a value exactly • Solution: Because difference is small, so ignore it XiaoLong He Network Available Bandwidth Measurements

  41. Future Works • How to measure available bandwidth of a host whose history information is not available. • How to find a better available bandwidth estimation formula to improve the accuracy of SMRT • Convert MMRT, SMUT and MMUT simulation code from Java to C • More traffic route to test the reliability of SMRT and other methods XiaoLong He Network Available Bandwidth Measurements

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