Network Topologies

Network Topologies

Network topologies are an important part of the network. Without the proper topology, the network may not meet the needs of the organization. The layout of a network is referred to as the topology. How nodes in a network are connected to each other and communicate is determined by the topology. There are three basic topologies with several typical variations, or combinations. A description of four topologies follows.

Mesh Topology

Mesh topology is the first topology discussed. In a mesh topology, the devices are connected with many redundant interconnections between nodes. Each device in the mesh topology is connected to every other device in the network. The mesh topology is the most expensive to implement but is also the most fault tolerant (Johnson, Tittel, and Tomsho, 2004). If any one cable or device within the mesh topology network fails, performance is not affected because of the multiple connections to other devices.

Bus Topology

When every workstation is connected to a main cable (bus), this is referred to as the bus topology. The bus topology has one common cable connection, also called the "backbone", to connect all the devices of the network. The single "backbone" acts as a shared communication medium that have other devices attached to it or tapped into it with a connector. The bus topology is the most commonly used topology and offers many benefits, but is a little outdated. Using the bus topology, any computer can be accessed directly and messages sent in a simple and fast way. The bus topology is simple and reliable, and the cabling is inexpensive and easy to work with. Disadvantages to the bus topology include; heavy traffic slows down the network, a scheduler is needed to assign frequencies and priorities to control the traffic, and any broken cable can bring down the entire network.

Ring Topology

With a ring topology, each node is connected to two other nodes to create a "ring". Data travels around the ring until it reaches its final destination. Ring networks are not as efficient as other networks because data has to pass through many points before reaching the destination. Data is transferred quickly without congestion. All computers have the same amount of access to the rest of the network. Disadvantages to the ring topology are, failure of the network if one computer fails, isolating problems with the network is difficult, and the addition or subtraction of computers to or from the network causes disruption in the network.

Star Topology

The star topology consists of one central switch, hub, or router to transmit messages. The computer will send a signal to the hub, which receives and then retransmits the message to all the other computers or devices attached to the hub. Good performance is an advantage to using the star topology. Centralization of resources, ease of set up and expansion, and the network still performs properly when one computer fails are all advantages to the star topology. The expense of installation, extra hardware required, and if the central hub fails the entire system fails, are disadvantages to the star topology.

Ethernet

Ethernet is a network technology for local area networks (LAN). "Ethernet uses a bus or star topology and supports data transfer rates of 10Mbps."(Webopedia, 2007). Ethernet is the most popular architecture used today. One advantage to Ethernet is the ease of installation. Ethernet costs less than other network architectures and is easy to use. Ethernet supports many different kinds of networking media, which makes it more popular than other architectures. Disadvantages to Ethernet networks are that they are not as efficient or as fast as other networks.

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