Topologies used for large networks

Any device connected to a networkis referred to as a node. All nodes are connected to the network either by wire or wirelessly.

A network's topologyis the arrangement, or pattern, in which all nodes on a network are connected together. There are several common topologies that are in use, but today the most common topologies are:

• star topologies
• mesh topologies

Star topologies are used in many networks, large and small.

In a star topology all nodes indirectly connect to each other through one or more switches. The switch acts as a central point through which all communications are passed.

Large networks using a star topology are usually controlled by one or more servers. Hence, the client-servermodel usually uses a star topology. However, peer-to-peernetworks can also have a star topology. Even though no single computer controls the network, all communications still pass through the central switch.

Advantages and disadvantages of using a star topology

Having nodes arranged in a star topology brings some benefits:

• each node is separately connected, therefore a failure of one node or its link, (transmission media), does not affect any other nodes
• new nodes can be added to the network simply by connecting them to the switch
• star networks tend to have higher performance as a message is passed on to its intended recipient only

However, star topologies also have their disadvantages:

• the whole network fails if the switch fails as no node can communicate
• a wired star topology requires plenty of cable - in a large network this can be expensive

Star topologies in use

Star topologies tend to be found in large organisations, such as educational establishments and businesses, where high performance is a must.

They are also found in home networks, especially those that are wireless. In this case, a routerwith a wireless access point (WAP)provides the central connection for all nodes.