# Fast Ethernet Definitions

HALF DUPLEX: This refers to the familiar Ethernet collision domain in which multiple hosts communicate over a single physical segment by detecting collisions and randomly taking turns using the medium. In the subnet, successful packets can flow in both directions between the hosts but may only flow in one direction at a time. A half-duplex Fast Ethernet segment uses an unshielded twisted pair (UTP) of copper wires to interconnect hosts.

FULL DUPLEX: This term refers to the communication between two devices when packets flow in both directions simultaneously. Full-duplex Fast Ethernet connections are intended to support the high speed, unblocked interchange of massive amounts of data. To accomplish this, two separate paths are used for data flowing in each direction. With a data clock rate of 100 MB, this means that full-duplex Fast Ethernet connections may interchange data at rates up to 200 MB. This method of communication is point-to-point and dedicated. That is, full-duplex only connects two devices so there is no sharing of the medium. Full-duplex Fast Ethernet connections may use either copper or fiber-optic cables.

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