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Spirent TestCenter: Why some frame sizes cannot match offered load with intended load?

Environment/Versions
  • Spirent TestCenter
    • RFC-2544
Answer
  • Easiest way to explain is by example.
  • Lets take a 9216 byte frame size with Intended load to be 99.98%
  • RFC-2544 will indicate the offered load to be 99.979% and the reason is shown below:
    • Theoretically 99.98% on a 10G port is 9.998Gbps.
    • Convert the frame size to bits (9216+20)*8 = 73888 bits
    • 9.998Gbps / 73888 bits = 135312.906 fps
    • Since the offered load should not go over the intended load rounding down gives 135312 fps.
    • Theoretical max of 10G for 9216 byte frame is 10G / 73888 = 135339.974 fps
    • Divide the maximum frames we can send at 99.98% which is 135312 by the Theoretical max of 135339.974 then we have:
      • 135312 / 135339.974 = 0.99979 = 99.979%

Product : Spirent TestCenter,RFC 2544