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One-way DelayMeasurement and Accuracy of the Network Time Synchronization

One-way DelayMeasurement and Accuracy of the Network Time Synchronization. Vladimir Smotlacha vs@cesnet.cz TF-NGN, April 2002. Measurement of the Accuracy. local clock of workstation is synchronized to (far) time server by a method, which is tested

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One-way DelayMeasurement and Accuracy of the Network Time Synchronization

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  1. One-way DelayMeasurement and Accuracy of the Network Time Synchronization Vladimir Smotlacha vs@cesnet.cz TF-NGN, April 2002

  2. Measurement of the Accuracy • local clock of workstation is synchronized to (far) time server by a method, which is tested • workstation is provided by PPS (Pulse Per Second) signal • timestamp of each PPS is evaluated • sub-second part of timestamp is actual offset of local clock

  3. Setup of the Measurement Time Synchronized server -------- network --------- box <--- PPS

  4. Current Results

  5. accuracy of NTP client client: Cesnet server: Heanet Current Results II

  6. OWD Measurement • two workstation: traffic generator and receiver • clock synchronization • time • frequency • clock synchronization accuracy - limiting factor for one-way measurement

  7. Organization of Measurement • boxes A and B synchronized to NTP server(s) • OWD = the difference between both timestamps • option: calculation of exact OWD if both A and B are supplied by PPS • option: comparison with RIPE TTM results, if RIPE box is available

  8. OWD Measurement Setup I + II NTP_ A NTP_B | | Box_A ----- network ----- Box_B NTP_A | Box_A ----- network ----- Box_B ( <-- PPS )

  9. OWD Measurement Setup III NTP_A ----- network ----- NTP_B | | institute A netw. institute B netw. | | NTP_A_sec NTP_B_sec | | (PPS --> ) Box_A Box_B ( <-- PPS)

  10. Box Specification • at least Pentium 120, Pentium II preferred • Linux kernel 2.4.16 with nanokernel patch • NTP package (4.1.71) • Rude/Crude 5.0 or 6.0 • PPS available at DCD pin of serial port

  11. Plans • setup boxes for OWD measurement • test commercial systems - NetIQ, IPANEMA • compare our method with others available (NetIQ, IPANEMA, RIPE TTM)

  12. Participants • HEAnet (Ireland) • GARR (Italy) • FOKUS (Gremany) • CESNET (Czech Republic) • cooperation with RIPE TTM

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