What is the purpose of Network Topology ?
A network is a collection of computers and devices connected by communication channels that allow users to share the data, information, hardware and software with other users, as well as to facilitate communications. People connect computers to a network for a variety of reasons.
Computer network topology is the way various components of a network (like nodes, links, peripherals, etc.) are arranged. Network topologies define the layout, virtual shape or structure of network, not only physically but also logically. The way in which different systems and nodes are connected and communicate with each other is determined by topology of the network. Topology can be physical or logical. Physical Topology is the physical layout of nodes, workstations and cables in the network; while logical topology is the way information flows between different components.
In general, physical topology relates to a core network whereas logical topology relates to basic network.
SIZE OF A NETWORK
A network can be as small as a LAN (local area network) consisting of some computers, printers and other devices or it may consist of many small and large computers distributed over a vast geographical area, i.e ., wide area network. Internet is also an example of wide area network.
The computer networks are classified according to the network topology based on the network. Network topology is the link of the devices in the network that are related to each other without any physical arrangement. There are four types of network topologies, namely:
👉 Star Network Topology
👉 Ring Network Topology
👉Bus Network Topology
👉Mesh Network Topology
Let us learn about these topologies in detail :-
STAR NETWORK TOPOLOGY
In Star Network, Topology, all the components of the network are connected to the central device called ‘hub’ which may be a hub, a router or a switch. All the workstations are connected to central device with a point-to-point connection. So, it can be said that every computer is indirectly connected to every other node by the help of ‘hub’.
All the data on the star topology passes through the central device before reaching the intended destination. Hub acts as a junction to connect different nodes present in Star Network, and at the same time it manages and controls whole of the network. Depending on which central device is used, ‘hub’ can act as repeater or signal booster. Central device can also communicate with other hubs of different network. Unshielded Twisted Pair (UTP) Ethernet cable is used to connect the workstations to the central node.
Advantages of Star Topology :
👉 As compared to Bus topology it gives far much better performance, signals don’t necessarily get transmitted to all the workstations. A sent signal reaches the intended destination after passing through no more than 3-4 devices and 2-3 links. Performance of the network is dependent on the capacity of the central hub.
👉 Easy to connect new nodes or devices. In star topology new nodes can be added easily without affecting rest of the network. Similarly, components can also be removed easily.
👉 Centralized management. It helps in monitoring the network.
👉 Failure of one node or link doesn’t affect the rest of the network. At the same time it is easy to detect the failure and troubleshoot it.
Disadvantages of Star Topology
👉 Too much dependency on central device has its own drawbacks. If it fails, whole network goes down.
👉 The use of hub, a router or a switch as central device increases the overall cost of the network.
👉 Performance as well as the number of nodes which can be added in such topology is dependent on the capacity of the central device.
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RING NETWORK TOPOLOGY
A Ring Network Topology is a network topology in which each device is connected to exactly two other devices. This forms a ring pattern.
This topology provides only one pathway between two devices. If one of the devices fails, the whole network will fail. It does not require any network server to manage the connectivity between the devices. It is much more reliable than bus network topology. Its biggest disadvantage is that it is not easy to add or remove any device from the topology as the data transmission will be disturbed.
Advantages of Ring Topology
Transmitting network is not affected by high traffic or by adding more nodes, as only the nodes having tokens can transmit data. Cheap to install and expand.
Disadvantages of Ring Topology
Troubleshooting is difficult in ring topology.
Adding or deleting the computers disturbs the network activity. Failure of one computer disturbs the whole network.
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BUS NETWORK TOPOLOGY
Bus Topology is the simplest of network topologies. In this type of topology, all the nodes (computers as well as servers) are connected to the single cable (called bus), by the help of interface connectors. This central cable is the backbone of the network and is known as Bus (thus the name). Every workstation communicates with the other device through this Bus.
A signal from the source is broadcasted and it travels to all workstations connected to bus cable. Although the message is broadcasted but only the intended recipient, whose MAC address or IP address matches, accepts it. If the MAC / IP address of the machine doesn’t match with the intended address, machine discards the signal. A terminator is added at the ends of the central cable to prevent bouncing of signals. A barrel connector can be used to extend it.
Advantages of Bus Topology
👉 It is cost effective.
👉 Cable required is least compared to other network topologies. Used in small networks.
👉 It is easy to understand.
👉 Easy to expand joining two cables together.
Disadvantages of Bus Topology
👉 If cables fail, then the whole network fails.
👉 If network traffic is heavy or nodes are more, the performance of the network decreases.
👉 Cable has a limited length.
👉 It is slower than the Ring topology.
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MESH NETWORK TOPOLOGY
In a Mesh Network Topology, each of the network node, computer and other devices are interconnected with one another. Every node not only sends its own signals but also relays data from other nodes. In fact, a true mesh topology is the one where every node is connected to every other node in the network. This type of topology is Very expensive as there are many redundant connections, thus it is not mostly used in computer networks. It is commonly usedin Wireless networks. Flooding or routing technique is used in mesh topology. TherearetwotypesofMesh Topology.
These are :
👉 Partial Mesh Topology : In this topology, some of the systems are connected in the same fashion as mesh topology but some devices are only connected to two or three devices.
👉 Full Mesh Topology : Each and every nodes or devices are connected to each other.
Advantages of Mesh Topology
👉 Each connection can carry its own data load.
👉 It is robust.
👉 Fault is diagnosed easily.
👉 Provides security and privacy.
Disadvantages of Mesh Topology
👉 Installation and configuration is difficult.
👉 Cabling cost is more.
👉 Bulk wiring is required.
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