How does Drop frame duration calculates in VIAVI? 

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How does Drop frame duration calculates in VIAVI? 
It depends on the the frame size , Stream rate and drop count filed in Advance sequencer tab. This is how that drop count calculates for 128 byte frame (148 Bytes since there are 20 Bytes of preamble/SFD): • Drop Count * 148 Bytes * 8 bits = Number of  bits lost • Number of bits lost / stream rate = Drop Duration