Ethernet devices must allow a minimum idle period between transmission of Ethernet frames known as the interframe gap (IFG), interframe spacing, or interpacket gap (IPG). A brief recovery time between frames allows devices to prepare for reception of the next frame. The minimum interframe gap is 96 bit times (the time it takes to transmit 96 bits of raw data on the medium), which is 9.6 µs for 10 Mbit/s Ethernet, 0.96 µs for 100 Mbit/s (fast) Ethernet, 0.096 µs for 1 Gbit/s (gigabit) Ethernet, and 0.0096 µs for 10 Gbit/s (10 gigabit) Ethernet.
Several adapter manufacturers design their adapters with a smaller interframe gap for higher data transfer rates, which can lead to a high rate of collisions. An example is Intel EtherExpress 100B.
IFG Shrinking is allowed on repeaters towards the DTE (Data terminal equipment) and MII (Media Independent Interface) into the MAC (Media Access Control). This is to account for variable network delays, added preamble bits, and clock tolerances.
On reception, some interframe gaps may be smaller due to variable network delays, clock tolerances, and the presence of repeaters.
- For 10 Gigabit Ethernet received IFG can be reduced to a period of 40 bit times (5 bytes).
- For Gigabit Ethernet received IFG can be reduced to a period of 64 bit times (8 bytes).
- For Fast Ethernet received IFG is not specified.
- For Ethernet received IFG can be reduced to a period of 47 bit times.
Famous quotes containing the word gap:
“Here is the place; right over the hill
Runs the path I took;
You can see the gap in the old wall still,
And the stepping-stones in the shallow brook.”
—John Greenleaf Whittier (1807–1892)