Convert the 96-bit Ethernet interframe gap into nanoseconds at any line rate and see the bandwidth it costs.
The gap is specified in bit times, not seconds, so it shrinks as the link gets faster — 9.6 µs at 10 Mbps, 96 ns at 1 Gbps and 0.96 ns at 100 Gbps. Combined with the 64-bit preamble and SFD it burns 20 byte times before every frame, which is bandwidth you can never recover. The gap is why a 10 Gbps port cannot forward 14.88 million 64-byte frames plus anything else, and it is the term people forget when their measured throughput lands a few percent below the theoretical figure.
Interframe Gap
The interframe gap is fixed at 96 bit times, so its duration is 96 ÷ line rate; one bit time at R Mbps is 1000/R nanoseconds.
Bandwidth cost of the gap
overhead = 20 ÷ (frame bytes + 20).
The interframe gap is fixed at 96 bit times, so its duration is 96 ÷ line rate; one bit time at R Mbps is 1000/R nanoseconds. The gap is specified in bit times, not seconds, so it shrinks as the link gets faster — 9.6 µs at 10 Mbps, 96 ns at 1 Gbps and 0.96 ns at 100 Gbps. Combined with the 64-bit preamble and SFD it burns 20 byte times before every frame, which is bandwidth you can never recover.
The gap is why a 10 Gbps port cannot forward 14.88 million 64-byte frames plus anything else, and it is the term people forget when their measured throughput lands a few percent below the theoretical figure.
This calculator takes 3 inputs: Line rate, Average frame size, Frame rate. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.