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Advanced Network Diagnostic Tools

Advanced Network Diagnostic Tools. Richard Carlson Tier3 LHC workshops. Basic Premise. Application’s performance should meet your expectations! If they don’t you should complain!. Underlying Assumption. When problems exist, it’s the networks fault!. Simple Network Picture. Bob’s Host.

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Advanced Network Diagnostic Tools

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  1. Advanced Network Diagnostic Tools Richard Carlson Tier3 LHC workshops

  2. Basic Premise • Application’s performance should meet your expectations! • If they don’t you should complain!

  3. Underlying Assumption • When problems exist, it’s the networks fault!

  4. Simple Network Picture Bob’s Host Network Infrastructure Carol’s Host

  5. Switch 2 Switch 3 R5 R4 R8 R1 R3 R6 Switch 1 R9 R2 R7 Switch 4 Network Infrastructure

  6. Advanced user tools • Existing NDT tool • Allows users to test network path for a limited number of common problems • Existing NPAD tool • Allows users to test local network infrastructure while simulating a long path • NPToolKit Live-CD Knoppix disk • Bootable CD that contains all the tools described in this talk http://e2epi.internet2.edu/network-performance-toolkit.html

  7. Network Diagnostic Tool (NDT) • Measure performance to users desktop • Identify real problems for real users • Network infrastructure is the problem • Host tuning issues are the problem • Make tool simple to use and understand • Make tool useful for users and network administrators

  8. NDT sample Results

  9. NPAD/pathdiag • A new tool from researchers at Pittsburgh Supercomputer Center • Finds problems that affect long network paths • Uses Web100-enhanced Linux based server • Web based Java client

  10. Long Path Problem • E2E application performance is dependant on distance between hosts • Full size frame time at 100 Mbps • Frame = 1500 Bytes • Time = 0.12 msec • In flight for 1 msec RTT = 8 packets • In flight for 70 msec RTT = 583 packets

  11. Switch 2 Switch 3 R5 R4 R8 R1 R3 R6 Switch 1 R9 R2 R7 Switch 4 Long Path Problem H2 70 msec H1 – H3 1 msec H1 – H2 X H3 H1

  12. TCP Congestion Avoidance • Cut number of packets by ½ • Increase by 1 per RTT • LAN (RTT=1msec) • In flight changes to 4 packets • Time to increase back to 8 is 4msec • WAN (RTT = 70 msec) • In flight changes to 292 packets • Time to increase back to 583 is 20.4 seconds

  13. NPAD Server main page

  14. NPAD Sample results

  15. Network Admin Tools • BWCTL – Bandwidth Control • Allows single person operation over wide area testing environment • Runs NLANR ‘iperf’ program • OWAMP – One way Delay Measurement • Advanced ‘ping’ command • Allows single person operation over wide area testing environment

  16. PerfSonar – Next Steps in Performance Monitoring • New Initiative involving multiple partners • ESnet (DOE labs) • GEANT (European Research and Education network) • Internet2 (Abilene and connectors)

  17. Google it! • Enter “tuning tcp” into the google search engine. • Top 2 hits are: http://www.psc.edu/networking/perf_tune.html http://www-didc.lbl.gov/TCP-tuning/TCP-tuning.html

  18. PSC Tuning Page

  19. LBNL Tuning Page

  20. Conclusions • Primary tools still useful • Advanced tools are being developed • Developing tools will make things even easier • Demand 10 MB/s as the minimum acceptable throughput rate

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