Network Topology

              Is the study of the arrangement or mapping of the elements (links, nodes, etc.) of a network, especially the physical; the real, and logical; the virtual interconnections between nodes.

            A local area network (LAN) is one example of a network that exhibits both a physical topology and a logical topology. Any given node in the LAN will have one or more links to one or more other nodes in the network and the mapping of these links and nodes onto a graph results in a geometrical shape that determines the physical topology of the network. Likewise, the mapping of the flow of data between the nodes in the network determines the logical topology of the network. It is important to note that the physical and logical topologies might be identical in any particular network but they also may be different.

            The arrangement or mapping of the elements of a network gives rise to certain basic topologies which may then be combined to form more complex topologies (hybrid topologies). The most common of these basic types of topologies are;

• Star: The type of network topology in which each of the nodes of the network is connected to a central node with a point-to-point link in a 'hub' and 'spoke' fashion.
• Bus: (Linear, Linear Bus) the type of network topology in which all of the nodes of the network are connected to a common transmission medium which has exactly two endpoints.
• Ring: The type of network topology in which each of the nodes of the network is connected to two other nodes in the network and with the first and last nodes being connected to each other, forming a ring.

 

    I.                The Bus Topology

                  This type of network topology is generally used with Ethernet networks. Bus topology can be both Physical and Logical. The Bus topology is one of the simplest of the four network topologies to use, in its most basic form it is simply a case of running one cable (referred to as the backbone) from the first device/PC in the network to the last device/PC, and then add any further devices/PCs to the existing cable (backbone) between the first and last machines. This topology is probably the cheapest network type of all too initially setup, as only one cable is used the installation is fairly simple and economical.

 

 II.              The Ring Topology

       The physical ring topology is rarely used these days, a Ring topology networks the devices by connecting each device to its two neighboring devices Data is passed one way from device to device, fault tolerance in a physical ring topology is nonexistent, if one device/cable fails then the whole network goes down. Adding a new device to an existing physical Ring network can be complicated as any new device needs to go in between the existing devices.

 

 III.                The Star Topology

                      A physical Star topology connects the devices via a centralized unit such as a Hub or Switch. All data that is transmitted between nodes in the network is transmitted to this central node, which is usually some type of device that then retransmits the data to some or all of the other nodes in the network, although the central node may also be a simple common connection point (such as a 'punch-down' block) without any active device to repeat the signals. Star topologies are very common, especially in Ethernet networks; also, they are commonly mixed with one of the other topologies to create a hybrid topology.

 

 Resources:

 Resource: Information Systems Technology text