Thank you for that useless copy-and-paste from Wikipedia's article on interframe gaps, Fred.I would very much like to know the answer to the question posted. "What is the Inter-frame Gap in case of [...] FAST Ethernet and GIGABIT Ethernet?" with the emphasis clearly being on not what the 1970 recommendation was, but what is actually relevant to 21st century technology like Fast/Gigabit Ethernet and beyond.
Ethernet devices allow a minimum idle period between transmission of Ethernet frames known as the interframe gap (IFG). Providing 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, the time it takes to transmit 96 bits of raw data on the medium, which is 9.6 µs for 10 Mbit/s Ethernet, 960 ns for 100 Mbit/s (fast) Ethernet, and 96 ns for 1 Gbit/s (gigabit) Ethernet.