term repeater comes from the early days of long distance communication.
The term describes the situation when a person on one hill would
repeat the signal that was just received from the person on
the previous hill. The process would repeat until the message
arrived at its destination. Telegraph, telephone, microwave,
and optical communications use repeaters to strengthen signals
sent over long distances.
A repeater receives a signal, regenerates it, and passes it
on. It can regenerate and retime network signals at the bit
level to allow them to travel a longer distance on the media.
One downside of repeaters, though, is that they reduce throughput
on the LAN. A repeater must receive and retransmit each frame
on the same RF channel, which effectively doubles the number
of frames that are sent. This problem compounds when using multiple
repeaters because each repeater will duplicate the number of
frames sent. Thus, be sure to plan the use of repeaters sparingly.
The Four Repeater Rule for 10-Mbps Ethernet should be used as
a standard when extending LAN segments. This rule states that
no more than four repeaters can be used between hosts on a LAN.
This rule is used to limit loss added to frame travel by each
As a result, repeaters are an effective solution to overcome
signal impairments such as RF attenuation. For example, repeaters
provide connectivity to remote areas that normally would not
have wireless network access. You may have one access point
in a home or small office that doesn't quite cover the entire
area where users need connectivity, such as a basement. The
placement of a repeater between the covered and uncovered areas,
however, will provide connectivity throughout the entire space.
The repeater fills holes in coverage, enabling seamless roaming.