Network topologies are classified as physical, logical and signal topologies. A physical topology describes the mapping of the network nodes and the physical connections between them. Signal topology describes the paths, which the signals take while they pass over the network. The mapping of the paths taken by data as they travel over the network is known as a logical topology. The terms, signal topology and logical topology are closely related. Let us see the different types of network topologies in detail.
Bus Topology: In this type of network topology, all the nodes of a network are connected to a common transmission medium having two endpoints. All the data that travels over the network is transmitted through a common transmission medium known as the bus or the backbone of the network. When the transmission medium has exactly two endpoints, the network topology is known by the name, 'linear bus topology'. In case the transmission medium, also called the network backbone, has more than two endpoints, the network is said to have a distributed bus topology. Bus topology is easy to handle and implement and is best suited for small networks. But the downside of this topology is that the limited cable length limits the number of stations, thus limiting the performance to a less number of nodes.
Ring Topology: In a ring topology, every node in the network is connected to two other nodes and the first and the last nodes are connected to each other. The data that are transmitted over the network pass through each of the nodes in the ring until they reach the destination node. In a ring network, the data and the signals that pass over the network travel in a single direction. The dual ring topology varies in having two connections between each of the network nodes. The data flow along two directions in the two rings formed thereby. The ring topology does not require a central server to manage connectivity between the nodes and facilitates an orderly network operation. But, the failure of a single station in the network can render the entire network inoperable. Changes and moves in the stations forming the network affect the network operation.
Mesh Topology: In a full mesh network, each network node is connected to every other node in the network. Due to this arrangement of nodes, it becomes possible for a simultaneous transmission of signals from one node to several other nodes. In a partially connected mesh network, only some of the network nodes are connected to more than one node. This is beneficial over a fully connected mesh in terms of redundancy caused by the point-to-point links between all the nodes. The nodes of a mesh network require possessing some kind of routing logic so that the signals and the data traveling over the network take the shortest path during each of the transmissions.
Star Topology: In this type of network topology, each node of the network is connected to a central node, which is known as a hub. The data that is transmitted between the network nodes passes across the central hub. A distributed star is formed by the interconnection of two or more individual star networks. The centralized nature of a star network provides a certain amount of simplicity while also achieving isolation of each device in the network. However, the disadvantage of a star topology is that the network transmission is largely dependent on the central hub. The failure of the central hub results renders the entire network inoperable.
Tree Topology: It is also known as a hierarchical topology and has a central root node that is connected to one or more nodes of a lower hierarchy. In a symmetrical hierarchy, each node in the network has a specific fixed number of nodes connected to those at a lower level.
Apart from these basic types of network topologies, there are hybrid network topologies, which are composed of a combination of two or more basic topologies. These network mappings aim at harnessing the advantages of each of the basic topologies used in them. Network topologies are the physical arrangements of network nodes and wires. What is interesting is that the inanimate nodes and wires turn 'live' for the transmission of information!
