Interframe Gap and Throughput

Ethernet devices must allow a minimum idle period between transmission of frames known as the interframe gap (IFG) or interpacket gap (IPG). It provides a brief recovery time between frames to allow devices to prepare for reception of the next frame. The minimum interframe gap is 96 bit times, which is 9.6 microseconds for 10 Mb/s Ethernet, 960 nanoseconds for 100 Mb/s Ethernet, and 96 nanoseconds for 1 Gb/s Ethernet.

Let's assume a Gigabit port that can transfer raw data up to 125,000,000 bytes per second with minimum frame size of 64 bytes. The minimum inter frame gap period is 96 bits or 12 bytes which amounts to 96 nano seconds + 7 byte of preamble and 1 byte of delimiter consequence 84 bytes. 

Maximum Frame Rate and Throughput Calculations For a 1-Gb/s Ethernet Link

Frame Part	Minimum Frame Size	Maximum Frame Size
Inter Frame Gap (9.6 ms)	12 bytes	12 bytes
MAC Preamble (+ SFD)	8 bytes	8 bytes
MAC Destination Address	6 bytes	6 bytes
MAC Source Address	6 bytes	6 bytes
MAC Type (or length)	2 bytes	2 bytes
Payload (Network PDU)	46 bytes	1,500 bytes
Check Sequence (CRC)	4 bytes	4 bytes
Total Frame Physical Size	84 bytes	1, 538 bytes

[1,000,000,000 b/s / (84 B * 8 b/B)] == 1,488,096 f/s (maximum rate)

[1,000,000,000 b/s / (1,538 B * 8 b/B)] == 81,274 f/s (minimum rate)

Example Formula for Ixia  or other Test Device to find the exact linerate in bps-

=((Bytes Received Rate * 8) + (Frames Received Rate * 160))
where 160 bits (20 bytes) is the inter frame gap