Network Emulation

Paul Schopis
Senior Network Engineer
ITEC Ohio


September 5, 2001

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  1. Network Emulation
    Nistnet and it’s application to the ADEC satellite project

  2. Simulation
    • Advantages of simulation
      • (Can be) cheap and quick to assemble
      • Given sufficient computing resources, can do large-scale tests
      • tests are controlled, reproducible
    • Problems with simulation
      • Need to redo code for simulation environment
      • Simulation implementation may differ considerably from real one
      • Synthetic environment may also poorly represent real one.

  3. Emulator Architure (See Diagram)

  4. Used to test H.323
    • Tested platform with SmartBits.
    • All parameters were met with in a +/- 1 msec
      (Actual resolution ~.5msec)
    • With SmartBits we could verify switches etc. to further validate our findings.
    • Worst case is total accuracy within +/- 3msec.

  5. Our System Specs
    • Operating System: Linux Mandrake 7.2 Kernel recompiled and optimized for the device to be a router.
    • CPU: Pentium III 733Mhz
    • Memory: 256 MB
    • Motherboard: Asus CUSLC2-C AGP4X
    • NICS: Intel Etherpro 10/100
    • Emulator Software: Nistnet 2.1.0

  6. Findings
    • Latency does not matter
    • Drop is important but can tolerate up to 1%.
    • H.323 is very jitter intolerant.

  7. Drop Errored Seconds (See Diagram)
    Drop Errored Seconds
    Appliance NIC
    Percentage of Dropped Packets Errored Seconds per One Minute Sample Percentage of Dropped Packets Errored Seconds per One Minute Sample
    .05% 0 .05% 0
    .10% 0 .10% 0
    .25% 17 .25% 2
    .50% 0 .50% 6
    .75% 42 .75% 11
    1.00% 48 1.00% 25
    1.25% 58 1.25% 30
    1.50% 60 1.50% 35
    1.75% 60 1.75% 60
    2.00% 60 2.00% 60
    2.25% 60 2.25% 60
    2.50% 60 2.50% 60

  8. Recevery Times (See Diagram)

    Recevery Times
    Appliance NIC
    Percentage of Dropped Packets Seconds for Recovery Percentage of Dropped Packets Seconds for Recovery
    .01% 0 .01% 0
    .10% .5 .10% .5
    .25% .5 .25% .5
    .50% 3 .50% 1
    .75% 15 .75% 2
    1.00% 32 1.00% 2
    1.25% 60 1.25% 2
    1.50% 60 1.50% 7
    1.75% 60 1.75% 60
    2.00% 60 2.00% 60
    2.25%1 60 2.25%1 60

  9. Jitter Errored Seconds (See Diagram)

    Jitter Errored Seconds
    Appliance NIC
    IP Delay Variation in Milliseconds Errored Seconds Per Minute IP Delay Variation in Milliseconds Errored Seconds Per Minute
    10 ms 0 10 ms 5
    20 ms 0 20 ms 0
    30 ms 0 30 ms 25
    40 ms 4 40 ms 35
    50 ms 25 50 ms 20
    60 ms 53 60 ms 57

  10. Jitter Recovery Time (See Diagram)

    Jitter Recovery Time
    Appliance NIC
    IP Delay Variation in Milliseconds Recovery time in seconds IP Delay Variation in Milliseconds Recovery time in seconds
    10 ms 0 10 ms 0
    20 ms 0 20 ms .5
    30 ms .5 30 ms 1
    40 ms 1 40 ms 1
    50 ms 1 50 ms 9
    60 ms 2 60 ms 5

  11. MCU to Client Jitter Errored Seconds (See Diagram)

    MCU to Client Jitter Errored Seconds
    Appliance NIC
    IP Delay Variation in Milliseconds Errored Seconds per One Minute Sampling IP Delay Variation in Milliseconds Errored Seconds per One Minute Sampling
    10 ms 60 10 ms 21
    20 ms 60 20 ms 34
    30 ms 60 30 ms 24
    40 ms 60 40 ms 28
    50 ms 60 50 ms 60
    60 ms 60 60 ms 60

  12. MCU to Client Recovery Time for Jitter (See Diagram)

    MCU to Client Recovery Time for Jitter
    Appliance NIC
    IP Delay Variation in Milliseconds Recovery Times with 60 Second Maximum IP Delay Variation in Milliseconds Recovery Times with 60 Second Maximum
    10 ms 38 10 ms 18
    20 ms 27 20 ms 27
    30 ms 50 30 ms 60
    40 ms 60 40 ms 60
    50 ms 60 50 ms 60
    60 ms 60 60 ms 60