Which Fast Ethernet standard allows sending frames at 100 Mbps over Category 5E UTP or fiber optic cabling?

The standard that allows sending frames at 100 Mbps over Category 5E UTP or fiber optic cabling is IEEE 802.3u. This specification defines Fast Ethernet, which operates at the speed of 100 Mbps and is designed to be an upgrade to 10 Mbps Ethernet. It supports both twisted pair cabling (like Category 5E) and fiber optic connections, making it flexible for various networking environments.

The use of Category 5E cabling is particularly important, as it enhances data transmission capabilities while maintaining compatibility with existing Ethernet standards. IEEE 802.3u provides specifications that enable devices to communicate over these media efficiently, thus ensuring robust performance in local area network (LAN) setups.

In comparison, other standards listed focus on different aspects; for example, IEEE 802.3z is associated with Gigabit Ethernet, while IEEE 802.3ab specifies the use of 1000BASE-T, which extends Gigabit Ethernet speeds over twisted pair cabling. IEEE 802.3x deals with full-duplex operation and flow control, not the specific data rate of 100 Mbps.