Network topologies, what are they and what are the differences between them? These two questions form the basis for truly understanding the networking concepts and how data traverses a network. This paper is going to answer these questions to assist in better design and implementation of networks.
To start we must understand what a network topology is. In short a network topology is nothing more than a way of connecting devices to each other. Topology refers to the way that devices connect physically and logically. The standard topologies today are the bus, the ring, the star and the mesh topologies. These terms apply to both physical and logical topologies.
What is the difference between physical and logical topology? Think of a topology as the shape of the network. Physical topology refers to the way that devices physically connect to each other, the physical shape of the network; and the logical topology refers to the way that data and signals traverse the network, the virtual shape of the network. All networks have both a physical topology, or physical shape, and logical topology, or virtual shape; though the physical and virtual shapes may not be the same.
Some of the most common early topologies are the bus topology and the ring topology. Both of these topologies utilized the same topology for both the physical and logical topology. What this means is that if you implemented a bus topology for your network then both the physical and logical topology, or shape, would be that of a bus topology. They were fairly easy and inexpensive to set up.
A physical bus topology uses a common backbone to connect all devices. The backbone is a single cable that functions as a shared communication medium . All devices attach to the backbone and communications are broadcast to all devices at the same time. The intended recipient is the only device that can accept and process communications. In this way only one device can transmit at a time. When multiple devices try to transmit at the same time collisions occur on the bus, or backbone, and all communications come to a halt. This is compounded with more devices connected to the network. If a cable fails the entire network become unusable.
A physical ring topology is implemented with each device connected to exactly two of its neighbors. The last device on the network is connected to the first device on the network forming a loop or ring. All data is transmitted in the same direction, either clockwise or counter clockwise. For one device to communicate with another on the network, it must send the data forward through the network until the intended recipient receives the data. For any responses to come back they must continue to be sent forward around the network and come full circle back to the original device. The more devices on the network the longer this process takes. A failure of any cable or device on the network breaks the look and all communications cease to m...