Pchar: Child of Pathchar Bruce A. Mah bmah@ca.sandia.gov Security - - PowerPoint PPT Presentation

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Pchar: Child of Pathchar Bruce A. Mah bmah@ca.sandia.gov Security - - PowerPoint PPT Presentation

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Pchar: Child of Pathchar Bruce A. Mah bmah@ca.sandia.gov Security and Networking Research Department (8910) Sandia National Laboratories / California 21 July 1999 What can we learn about the network? Measure network characteristics

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Pchar: Child of Pathchar

Bruce A. Mah bmah@ca.sandia.gov Security and Networking Research Department (8910) Sandia National Laboratories / California 21 July 1999

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What can we learn about the network?

  • Measure network characteristics

– Bandwidth – Delay – Loss Rate – End-to-end or hop-by-hop

  • Constraints

– Algorithms execute on endhosts only – Avoid disrupting existing network traffic – Avoid depending on specific network protocols

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Existing Work

  • Ping (Mike Muuss, ARL)

– Round-trip times only

  • SNMP

– Detailed information at intermediate network nodes – Requires administrative access on routers

  • ttcp, netperf, et al.

– TCP-specific – Large TCP bulk transfers can disrupt network

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Existing Work, Continued

  • Traceroute (Van Jacobson)

– Like ping, but uses IP TTL to discover routing information, round- trip times

  • Pathchar (Van Jacobson)

– Try to characterize individual network hops

  • Delay
  • Available bandwidth
  • Queuing
  • Loss
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pchar: Child of Pathchar

  • An independent implementation of pathchar
  • Based on pathchar algorithms

– ftp://ftp.ee.lbl.gov/pathchar/msri-talk.ps.gz

  • Designed as a framework for examining different

measurement and analysis algorithms

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pchar/pathchar measurements

  • Send UDP packets along path, wait for ICMP responses
  • Vary IP TTL to control how far into network packets can

travel: gives links traversed

  • Varying packet sizes gives bandwidth and latency
  • Multiple repetitions give queuing and loss information
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pchar Output

Path to cs.berkeley.edu (169.229.60.56) Packet size increments by 32 to 1500 46 test(s) per repetition 32 repetition(s) per hop 0: Partial loss: 0 / 1472 (0%) Partial char: rtt = 0.653832 ms, r2 = 0.992239 Hop char: rtt = 0.653832 ms, bw = 21678 Kbps, r2 = 0.992239 Partial queueing: avg = 0.000194 ms (526 bytes) 1: 146.246.243.254 (con243.ca.sandia.gov) Partial loss: 0 / 1472 (0%) Partial char: rtt = 0.871580 ms, r2 = 0.992828 Hop char: rtt = 0.217748 ms, bw = 89483 Kbps, r2 = 0.787175 Partial queueing: avg = 0.000257 ms (560 bytes) 2: 146.246.250.254 (snl-outnet.ca.sandia.gov) Partial loss: 0 / 1472 (0%) Partial char: rtt = 0.783626 ms, r2 = 0.982747 Hop char: rtt = -0.087954 ms, bw = 172435 Kbps, r2 = 0.296921 Partial queueing: avg = 0.019788 ms (39197 bytes)

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pchar Output, Continued

. . 10: 128.32.120.181 (f1-0.inr-181-soda.Berkeley.EDU) Partial loss: 0 / 1472 (0%) Partial char: rtt = 5.956725 ms, r2 = 0.949262 Hop char: rtt = -0.071023 ms, bw = 108351 Kbps, r2 = 0.044718 Partial queueing: avg = 0.001376 ms (1112 bytes) 11: 128.32.40.202 (128.32.40.202) Partial loss: 0 / 1472 (0%) Partial char: rtt = 6.673852 ms, r2 = 0.986403 Hop char: rtt = 0.717128 ms, bw = 7960 Kbps, r2 = 0.892486 Partial queueing: avg = 0.001291 ms (575 bytes) 12: 169.229.60.56 (cs2.CS.Berkeley.EDU) Path length: 12 hops Path char: rtt = 6.673852 ms, r2 = 0.986403 Path bottleneck: 7960.846285 Kbps Path pipe: 6641 bytes Path queueing: average = 0.001291 ms (575 bytes)

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One-hop Packet Response Times

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Two-Hop Packet Response Times

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Partial Path and Per-Hop Characteristics

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Future Work

  • New or improved measurement algorithms

– Reduce impact on the network – Reduce measurement time – Produce useful results over switched networks

  • New or improved analysis algorithms

– Reduce the effects of experimental errors – Adaptive analysis and measurement

  • Programming interface (API) for applications
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Where to get it?

  • Web:

– http://www.ca.sandia.gov/~bmah/Software/pchar/

  • Email:

– bmah@ca.sandia.gov

  • Platforms currently supported:

– FreeBSD, Solaris, Linux, IRIX

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Finis

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Diversity in Networks is Increasing

The Internet is becoming increasingly heterogeneous.

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Who Cares?

  • Applications

– Network video: set coding parameters – Collaboration applications: set data resolution – Distributed resource managers: Find network resources

  • Network managers, architects, and researchers

– How well is the network working under current load?