Network topology means the physical layout of a LAN. It includes geometrical arrangement of computer resources, remote devices and communication facilities. Each device or computer in the network is called a node. Following topologies are most common for local area networking
Star topology – In this topology host computer is the server of the network. This host can be mainframe or a smaller computer. The printer and the database are the parts of this host computer. It is located in center of the network and all other nodes are connected to it. All the messages are routed through the host. In case of its failure, the whole network fails.
Ring topology – In this arrangement, all the nodes are connected in a circle. The network has no host computer. The message travels along the ring connectivity in one direction or both the directions and reaches a particular computer to which it is addressed. In case of failure of ring connection, the entire network starting from the faulty device to the end of chain fails.
Bus topology – Bus topology does not consist of a host computer instead each node forms an independent part of the network. The messages are transmitted from one node to another without travelling through any other unaddressed node. In this case, the network does not fail even if more or more computers fail.
Tree topology – It consists of several computers linked in a hierarchical manner. The messages are transmitted from the main computer to the terminal computers, from where it is transmitted onward to other nodes. In this case if main computer fails, the entire network is rendered inoperative. However, it is easier to isolate a defective node or the entire branch from the main computer.
Mesh topology – In this topology, each workstation has to send message frequently to all other workstations. It has a few main sites and a large number of remote offices or sites. This topology is very infrastructure-extensive and needs periodic maintenance for all the multiple connection points, however it's the fastest operating topology.