A network topology is the pattern in which nodes (i.e., computers, printers, routers or other devices) are connected to a local area network (LAN) or other network via links (e.g., twisted pair copper wire cable or optical fiber cable).
There are four principal topologies used in LANs: bus, ring, star and mesh. The most widely used of these is bus, because it is employed by Ethernet, which is the dominant LAN architecture. In a bus topology all devices are connected to a central cable, called the bus or backbone. This topology is relatively inexpensive and easy to install for small networks.
In a ring topology each device is connected directly to two other devices, one on either side of it, to form a closed loop. This topology is relatively expensive and difficult to install, but it offers high bandwidth and can span large distances. A variation is the token ring, in which signals travel in only one direction around the loop, carried by a so-called token from node to node.
In a star topology all devices are connected directly to a central computer or server. Such networks are relatively easy to install and manage, but bottlenecks can occur because all data must pass through the central device.
The mesh topology can be either a full mesh or a partial mesh. In the former, each computer is connected directly to each of the others. In the latter, some computers are connected to most of the others, and some are connected only to those other nodes with which they exchange the most data.
The several basic network topologies can be combined in various ways to form hybrid topologies, such as a ring-star network or a tree network. The latter consists of two or more star networks connected to a linear bus.
The word topology comes from the Greek words topos meaning place and logos meaning study. It is a description of any locality in terms of its layout. Topology is a branch of mathematics concerned with properties of geometric figures that are distorted without tearing or bonding together.
Created November 2, 2005.