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What is meant by network topology? What are the common layouts of network topology?

Various elements of a computer network such as links, nodes and so on are arranged in a way that is called a network topology.

To say, “the network topology defines the topological structure of a network”.

There are two ways of depicting a network topology. It can be either depicted logically or physically.
1. Physical Topology:
– This way refers to the placing of the various components of the network such as cable installation and device location.
– This actually defines the shape of the layout of the cable that will be used for linking the devices in the network.
– This includes the layout of the cabling, nodes – their locations and interconnections between them and cabling.
– What defines the physical topology of a network? It is the capabilities of the network of accessing media and device, level of control, fault tolerance desired, associated cost and telecommunication circuits.

2. Logical Topology:
– This way refers to the representation of the data flow within the network.
– This is independent of the physical design of the topology.
– This defines the way the signals actually act up on the media of the network and the way of passage of data from device to device without concerning about the how the devices are physically interconnected.
– It is not necessary that both the physical and logical topology should be the same, they may differ.

Any two networks might differ in the terms of physical interconnections, signal types or distances between the nodes etc. but it is possible for them to have identical topologies. Distances between nodes, physical interconnections, transmission rates, and/or signal types may differ between two networks, yet their topologies may be identical topologies. The logical and the physical classification of the topologies is quite same with the only difference that the logical classification is based up on the path taken by data whereas the physical classification is based up on the actual physical path available between the devices. Network protocols determine the logical topologies as opposed to physical topologies being defined by the cabling layout, devices and so on. An association between the logical topologies and media access control methods and protocols is often made.

Basic Network Topologies

So far, 8 basic topologies have been defined:
1. Point–to–point:
– This represents the simplest permanent link between any two points.
– For e.g., switched point–to–point topology used in telephony.
– It follows Metcalfe’s law.
– It appears to users as a point – to – point communication channel.
– Using technologies such as packet switching and circuit switching, a point- to – point circuit can be created and destroyed when no longer needed.
– This topology represents the basic telephony mode.

2. Bus:
– Every node is given connection to a single cable and every system is given a single bus cable connection.
– Data from the source is transmitted to all the connected systems on the bus until the desired recipient is found.
– If no match is found between the intended address and the system address the data is simply ignored by the system.

3. Star:
– Each system on the network is given a connection to the main hub via a point – to – point connection.
– In this topology every node is connected to the central hub.

4. Ring:
– The systems are connected in a circular fashion and the data travels in one direction plus each device acts as a repeater.

5. Mesh:
This topology can be classified further into two types namely fully connected and partially connected.

6. Tree:
– This topology is formed by the combination of the star and bus topology for example, cable TV technology.
– This topology is often used in wireless networking for mobile applications, mining and military purposes.

7. Hybrid:
– This is the combination of two or more topologies in such a way that the resulting topology does not match any of the standard topologies.

8. Daisy chain:
– This is the easiest way for adding systems to a network.

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