Ethernet is a networking technology. It is CSMA/CD, or
Carrier Sense, Multiple Access,
Collision Detect. All
hosts on an ethernet segment can hear all
communication going on. When a
host wants to
transmit, it checks to see if other transmissions are going on. Hence, the carrier sense part. If none are going on, it transmits. If all goes well, the transmission will be heard by all hosts on the segment, including the host the transmission was intended for. This is the Multiple Access part. If two hosts happen to transmit
at the same time, a
collision will ocurr, and both hosts will wait a
random amount of time before transmitting
again. This is the
collision detect part.
Ethernet hardware addresses are 48
bits long, or six bytes. They are usually written in
hex as follows: 2A:3F:00:11:55:2F. All ethernet interface manufacturers turn to a central registry to get addresses, to
ensure that no two devices ever have the same
hardware address. It is the
ethernet controller's job to only pass along two types of
frames to the host: Those with its destination address, and broadcast frames. All others should be ignored. This job can be extended to pass all frames along to the host, which is known as promiscuous mode, and is used to debug network problems and spy on people.
Ethernet can travel over many different
media, at different
signalling rates. The most common ethernet signalling rate is 10 megabits per second, which can travel over
10base-2,
10base-5,
10base-T, and so on. Then you have
fast ethernet and
gigabit ethernet, which have higher signalling rates, and hence, different media.
Ethernet is a
layer 2 protocol in the OSI network model.