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What is the formula for calculating Interburst Gap (IBG)?”


If using the Spirent TestCenter Application set with Scheduling mode as Port based you can see the IBG in the Port Load window.

Formula comes from RFC 2889 based on a single frame size (see below).

A.1 Calculating the InterBurst Gap


   IBG is defined in RFC 2285 [2] as the interval between two bursts.

   To achieve a desired load, the following Input Parameter need to be



     LENGTH - Frame size in bytes including the CRC.


     LOAD   - The intended load in percent.  Range is 0 to 100.


     BURST  - The number of frames in the burst (integer value).


     SPEED  - media's speed in bits/sec

                 Ethernet is 10,000,000 bits/sec

                 Fast Ethernet is 100,000,000 bits/sec

                 Gigabit Ethernet is 1,000,000,000 bits/sec


     IFG    - A constant 96 bits for the minimum interframe gap.


   The IBG (in seconds) can be calculated:



          [(100/LOAD - 1) * BURST * (IFG + 64 + 8*LENGTH)] + IFG

   IBG = -----------------------------------------------------------


See also related article FAQ10741


Product : PGA