An Introduction To Network Topology

An Introduction To Network Topology In the context of a communication network, the term topology refers to that way in which the end points, or stations, attached to the network are interconnected or it is the arrangements of systems in a computer network. It can be either physical or logical. The physical topology refers that, a way in which a network is laid out physically and it will include the devices, installation and location. Logical topology refers that how a data transfers in a network as opposed to its design. The network topology can be categorized into bus, ring, star, tree and mesh. Hybrid networks (They are the complex networks, which can be built of two or more topologies). Bus Topology A Bus topology is characterized by the use of a multi point medium. A long and single cable acts as a backbone to connect all the devices in a network. In a bus topology, all computers or stations attach through the appropriate hardware interfacing known as a tap, directly to a bus network. Full duplex operation between the station and tap allows data to transmit onto the bus and received from the bus. A transmission from any station propagates the length of the medium in both directions and can be received by all other stations. At each end of the bus is a terminator, which absorbs any signal, removing it from the bus. Nodes are connected to the bus cable by drop lines and taps. A drop line is a connection running between the device and the main cable. A tap is a connector that either splices into the main cable or punctures the sheathing of a cable to create a contact with the metallic core. A bus network work best with a limited number of computers. Advantages Bus topology can install very easily on a network. Cabling will be less compare to other topologies because of the main backbone cable laid efficiently in the network path. Bus topology suited for a small network. If one computer fails in the network, the other computers are not affected they will continue to work. It is also less expensi ve than star topology. Disadvantages The cable length will limited and there by limits the number of stations. If the backbone cable fails, the entire network will goes down. It is very difficult to trouble shoot. Maintenance cost is very high in a long run. Terminators are required for both the ends of the cable. Ring topology The ring topology the network consists of dedicated point to point connection and a set of repeaters in a closed loop. A signal is passed along the ring in one direction, from device to device, until it reaches its destination. It may be clock wise or anti clock wise. When a device receives a signal intend for another device, its repeater generates the bits and passes them along. As with the bus and tree, data are transmitted in frames. As a frame circulates past all the other stations, the destination station recognize its address and copies the frame into a local buffer as it goes by. The frame continues to circulate until it returns to the source station, where it is removed. These topologies are used in school campuses and some office buildings.