12 hours Beginners
Network topology is the structural layout of a network, which consists of various elements of a computer network. Network topology is two types physical and logical. Physical topology is the physical design of the network including various device,cable installation and their location. Logical topology show how data is actually transferred in a network. Topology show only the virtual shape or structure of a network. It doesnot actual physical design of the devices on the network.Factors to be considered while selecting a network topology.
• Cost : For a network to be cost effective, one would try to minimize installation cost. This may be achieved by using well understood media and also, to a lesser extent, by minimizing the distances involved.
• Flexibility : Because the arrangement of furniture, internal walls etc. in office is often subject to change, the topology should allow for easy recognition of the network . This involves moving existing nodes and adding new ones.
• Reliability : Failure in a network can take two forms. Firstly, an individual node can malfunction. This is not nearly as serious as the second type of fault where the network itself fails to operate. The topology chosen for the network can help by allowing the location of the fault to be detected and to provide some means of isolating it.There are different types of topologies.
In bus topology all nodes are connected to the central cable or called backbone cable.Each computer or server is connected to the single bus cable through some kind of connector. A terminator is required at each end of the bus cable to prevent the signal from bouncing back and forth on the bus cable. In this topology if any node goes faulty then all nodes may be stop work.
In ring topology all nodes are connected to one another in the shape of a closed loop,so that each node is connected directly to two other nodes, one on either side of it. Data is transmitted around the ring in one direction only;each node passing on the data to the next station till it reaches its destination.
Information travels around the ring from one node to the next. Each packet of data sent on the ring is prefixed by the address of the station to which it is being sent. When a packet of data arrives, the node checks to see if the packet address is the same as its own, if it is, it graps the data. If the packet does not belong to it, it sends the packet to the next node int the ring. Example is token ring.Advantages of ring topology
In start topology all nodes are connected to a central device it may be hub or switch. A star topology take more cable since Every node has its own dedicated connection to the central device.
Tree topology combine features of Star and Bus Topology. It has a central node(Hub/Switch) and all other nodes are connected with this central node to form a hierarchy. It is also called hierarchical topology. Star Topology ensures that if one node goes down, all the rest are operational because it is direct linking with central node. A cable TV network has such a topology, with the main feed cable getting divided into smaller branches, which ultimately reach homes.
In mesh topology each computer and network device is interconnected with one another, allowing for most transmissions to be distributed, even if one of the connections go down. The number of connections in this network can be calculated using the following formula (n is the number of computers in the network): n(n-1)/2. It is not widely used in computer network.
If two or more network topology combine to one topology then it's called Hybrid topology. In this topology good feature of one topology is combine with good feature of other topology. This combination of topologies is done according to the requirements of the organization.
For example if one department ring topology is used and in another department star topology is used, connecting these topologies will result in Hybrid Topology (ring topology and star topology).
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