Page 71 - M. Abrahim Thesis

Computer Network 2021

Half-duplex transmission is an improvement over simplex transmission; the traffic can
travel in both directions. Half-duplex transmission enables signals to travel in either direction,
but not in both directions simultaneously, as illustrated in Figure 3-18. Half duplex Ethernet,
defined in the original 802.3 Ethernet, uses only one wire, with a digital signal running in both
directions on the wire. It allows data transmission in only on direction at a time between a
sending station and a receiving station. It also uses the CSMA/CD protocol to help prevent
collisions and retransmit if a collision does occur.

Figure 3-18 shown a Half-Duplex Transmission

Full-duplex transmission, as illustrated in Figure 3-19, operates like a two-way, two lane
street. Traffic can travel in both directions at the same time. Ethernet full-duplex operation is
made possible using switch technology. Full-duplex switched networking technology increases
performance because data can be sent and received at the same time. Full-duplex Ethernet uses
two pairs of wires, which allow simultaneous data transmission between a sending station and
a receiving station. Virtually no collisions occur in full-duplex Ethernet because switching
technology creates a two-station point-to-point virtual circuit, or “microsegments,” when two
devices need to communicate.

Full-duplex Ethernet is supposed to offer 100 percent efficiency in both directions. This
means that you can get 20 Mbps with a 10-Mbps Ethernet running in full-duplex operation.

A 100-Mbps switch potentially can offer 200 Mbps to a station in full-duplex mode.

Figure 3 - 19 shown a Full - Duplex Transmission

https://www.youtube.com/watch?v=TIiQiw7fpsU

3.7.6 Ethernet Timing

Ethernet was designed to operate on a bus structure, which is a technical way to say that
every station always hears all messages at almost the exact same time. The official designation
is CSMA/CD. CSMA/CD can be interpreted simplistically to mean that when two stations realize
that they are talking at the same time, they are supposed to stop and wait a polite amount of
time before trying again. The basic rules and specifications for proper operation of Ethernet are

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