Specifications

Introduction 2-5
Ethernet Features
The most popular topologies used in Ethernet are the bus, star and tree.
Even though this discussion is about Ethernet, it is worth spending a few
moments on topologies not commonly used with Ethernet. A couple of
definitions at this point will assist with understanding the following
descriptions.
• Point-to-Point: A point-to-point connection is a connection between
two and only two network devices (computers, servers, printers, etc.).
No taps or daisy chains are allowed. The most common point-to-point
medias are twisted pair and fiber optics.
• Multi-point: A multi-point connection utilizes a single cable to connect
more than two network devices. A cable that has several devices
connected, one after another, (also known as daisy chaining) is an
example of a multi-point connection. The most common multi-point
media is coaxial cable.
Today’s networks employ various media topologies. The following
sections look at the general characteristics of the three most popular
topologies: bus, ring, and star.
Bus Topology
Employed in most older networks, the bus topology is a multi-point
network topology is which all devices are connected by a single common
cable or communications link. Taps are used to get the signal from the
coaxial cable to the device.
General Characteristics
Ethernet uses what is known as a contention bus topology. Any station on
the network can talk as long as no other station is talking. The more
stations that are on the network and want to talk, the worse the overall
performance. As a general rule, bus topologies are fairly straightforward
and easy to expand. Often, it is possible to expand the network without
affecting the network operation.
Vulnerability
Because all stations in the network share a common transmission media, a
failure of that media interrupts the exchange of signals between stations.
In a properly designed and constructed network however, such failures
are uncommon. Failure of a single workstation will not usually affect the
entire network.