Physical Topology means the physical design of a network including the devices, location and cable installation.
Logical Topology refers to the fact that how data actually transfers in a network as opposed to its design.
Topology can be considered as a virtual shape or structure of a network. This shape actually does not correspond to the actual physical design of the devices on the computer network. The computers on the home network can be arranged in a circle shape but it does not necessarily mean that it presents a ring topology.
Computer network topologies can be categorized in the following categories.
Hybrid networks are the complex networks, which can be built of two or more above mentioned topologies.
Bus topology uses a common backbone to connect all the network devices in a network in a linear shape. A single cable functions as the shared communication medium for all the devices attached with this cable with an interface connector. The device, which wants to communicate send the broadcast message to all the devices attached with the shared cable but only the intended recipient actually accepts and process that message.
Ethernet bus topologies are easy to install and don’t require much cabling and only a main shared cable is used for network communication. 10Base-2 and 10BaseT are two popular types of the Ethernet cables used in the Bus topology. Also, Bus network works with very limited devices. Performance issues are likely to occur in the Bus topology if more than 12-15 computers are added in a Bus Network. Additionally, if the Backbone cable fails then all network becomes useless and no communication fails among all the computers. Unlike in the Star topology in which if one computer is detached from a network then there is not effect on the other computers in a network.
In ring Network, every computer or devices has two adjacent neighbors for communication. In a ring network, all the communication messages travel in the same directory whether clockwise or anti clockwise. Any damage of the cable of any cable or device can result in the breakdown of the whole network. Ring topology now has become almost obsolete.
FDDI, SONET or Token Ring Technology can be used to implement Ring Technology. Ring topologies can be found in office, school or small buildings.
In the computer networking world the most commonly used topology in LAN is the star topology. Star topologies can be implemented in home, offices or even in a building. All the computers in the star topologies are connected to central devices like hub, switch or router. The functionality of all these devices is different. I have covered the detail of each networking devices in the separate portion of my website. Computers in a network are usually connected with the hub, switch or router with the Unshielded Twisted Pair (UTP) or Shielded Twisted Pair Cables.
As compared to the bus topology, a star network requires more devices & cables to complete anetwork. The failure of each node or cable in a star network, won’t take down the entire network
as compared to the Bus topology.
However if the central connecting devices such as hub, switch or router fails due to any reason,then ultimately all the network can come down or collapse.
Tree topologies are comprised of the multiple star topologies on a bus. Tree topologies integrate multiple star topologies together onto a bus. Only the hub devices can connect directly with the tree bus and each Hub functions as a root of a tree of the network devices. This bus/star/hybrid combination supports future expandability of the computer networks, much better than a bus or star.
Mesh topology work on the concept of routes. In Mesh topology, message sent to the destination can take any possible shortest, easiest route to reach its destination. In the previous topologies star and bus, messages are usually broadcasted to every computer, especially in bus topology. Similarly in the Ring topology message can travel in only one direction i.e clockwise or anticlockwise. Internet employs the Mesh topology and the message finds its route for its destination. Router works in find the routes for the messages and in reaching them to their destinations.The topology in which every devices connects to every other device is called a full Mesh topology unlike in the partial mesh in which every device is indirectly connected to the other devices.
Topologies are the important part of the network design theory. A better network can be built if you have the knowledge of these topologies and if you know the difference between each topology. Similarly you should have the knowledge of each network device so that you can properly use them according to your network needs. A misconfigured network can result in a waste of time and energy as well as a lots of troubleshooting methods to resolve the issue. So thebasic understanding of the network topologies and network devices is a must to build a good network.