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Things You Can Do in Budapest During Summer Time

Things You Can Do in Budapest During Summer Time. Aleksandar Kuzmanovic Rice University & Ericsson Traffic Lab October 2001. Budapest. Buda-Pest History Architecture Decadency … Ericsson Traffic Lab Unix Young people Security. People. Ericsson Traffic Lab, Budapest Andras Veres

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Things You Can Do in Budapest During Summer Time

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  1. Things You Can Do in Budapest During Summer Time Aleksandar Kuzmanovic Rice University & Ericsson Traffic Lab October 2001

  2. Budapest • Buda-Pest • History • Architecture • Decadency… • Ericsson Traffic Lab • Unix • Young people • Security Rice University & Ericsson Traffic Lab

  3. People • Ericsson Traffic Lab, Budapest • Andras Veres • EMULab, The University of Melbourne • Attila Pasztor, Darryl Veitch • Budapest University, Department of Physics • Gabor Simon, Gabor Vattay Rice University & Ericsson Traffic Lab

  4. My Goals • Modeling and reality? Rice University & Ericsson Traffic Lab

  5. Active Probing • Internal network inaccessible • Poor understanding of origins of complex network dynamics • Statistics is like the bikini… Goal: Estimate the sample path of cross-traffic Rice University & Ericsson Traffic Lab

  6. Background • Precise measurement infrastructure One way delay (sec) -> Packet departure time (sec) -> Rice University & Ericsson Traffic Lab

  7. Probing Uncertainty Principle • Should not allow queue to empty between probe packets • Small T for accurate measurements • but probe traffic would disturb cross-traffic (and overflow bottleneck buffer!) • Larger T leads to measurement uncertainties • queue could empty between probes Rice University & Ericsson Traffic Lab

  8. Theory • Lindley’s equation • CT information imbedded in delay • Ideal case: minimally backlogging condition [QK99] Rice University & Ericsson Traffic Lab

  9. Design Space • No time synchronization between end points $ 2.000.000.000 • Delay difference • Non-intrusiveness • Stability One way delay (sec) -> Time (sec) -> Rice University & Ericsson Traffic Lab

  10. Probing scheme Rice University & Ericsson Traffic Lab

  11. Aside… • Experiments on LAN • Time-sharing in Linux Inter-arrival time (sec) -> Time (sec) -> Rice University & Ericsson Traffic Lab

  12. Traffic Lab – Experiment Setup • Tcpdump, iperf (HTTP, TCP), sender, receiver… Rice University & Ericsson Traffic Lab

  13. Routes • Tech. University Budapest 6 nec2.ttt.bme.hu (152.66.247.2) 14.980 ms 14.212 ms 14.252 ms • Columbia University, NY 16 bongo.comet.columbia.edu (128.59. 64.210) 150.725 ms * 127.967 ms • University of Melbourne 23 potoroo.ee.mu.OZ.AU (128.250.76.186) 384.271 ms 383.408 ms 382.977 ms • Houston, we have a problem… -> One way delay (sec) -> Time (sec) -> Rice University & Ericsson Traffic Lab

  14. Wide Area vs. Metropolitan Area Network Rice University & Ericsson Traffic Lab

  15. Cross Traffic EstimationSample Path • Differentiate delay, know C • Cross traffic: from: Budapest to: NY iperf - 1 TCP • Probing traffic from: Budapest to: Melbourne Rice University & Ericsson Traffic Lab

  16. Cross Traffic EstimationMoving Average Rice University & Ericsson Traffic Lab

  17. Signs • Delay difference • => two queues • => two cases Rice University & Ericsson Traffic Lab

  18. Wide Area Network revisited • Differentiation btw. primary (256K) & secondary (transatlantic) bottlenecks • Secondary traffic underestimated for Csec./256K Rice University & Ericsson Traffic Lab

  19. Primary & Secondary Bottlenecks • LAN traffic controllable • Separation between primary (256K) & secondary (LAN) cross traffic Rice University & Ericsson Traffic Lab

  20. TCP Cross Traffic • Iperf (number of TCP connections >=3) • => delay decreases yet we see clusters of packet losses (queue size ~ delay~pck. loss?) Rice University & Ericsson Traffic Lab

  21. Role of packet sizes • => change packet size Rice University & Ericsson Traffic Lab

  22. Bit/sec. vs. Packet/sec. • Up: 540 Bytes • Down: 60 Bytes • 540/60 = 9 • 256Kbps*9= 2.3Mbps • UDP: 1500/30=50 • 256K*50= 12.8Mbps - 1.5M*50= 75Mbps Rice University & Ericsson Traffic Lab

  23. Secondary Bottleneck • Difference of CT estimate and tcpdump CT followed by clusters of packet losses Rice University & Ericsson Traffic Lab

  24. Role of TCP • Secondary CT (necessary for losses*) picks up the periodicity of probe traffic! • Through losses • Through delay • When phases match • Long burst of small packets causes losses on secondary bottleneck Rice University & Ericsson Traffic Lab

  25. Ongoing work • Short and long lived TCP connections • Heterogeneous TCP traffic… Rice University & Ericsson Traffic Lab

  26. Conclusions • Scalable,edge-based tool for on-line network analysis, modeling, and measurement • Scheme for estimating sample path of adaptive cross-traffic • Differentiation between primary and secondary bottlenecks: two queue model • Role of TCP (delay variation) and variable packet sizes • Low bit rate denial of service attack? • QoS in access networks (xDSL…) Rice University & Ericsson Traffic Lab

  27. The End Rice University & Ericsson Traffic Lab

  28. One more picture Rice University & Ericsson Traffic Lab

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