Introduction to Network Topology
Network topology is the arrangement of the elements of a communication network.It is a schematic description of a network arrangement. Topology defines the way different nodes are placed and interconnected with each other.It is a layout of connecting devices. This shape does not necessarily correspond to the actual physical devices on the network.There are two types of network topology, physical topology and Logical topology.Both physical and logical topology can be categorized in to five basic models.
Physical Topology
When in the context of networking, refers to the physical layout of the devices
connected to the network, including the location and cable installation.
Logical Topology
Defines how the hosts access the media to send data. Shows the flow of data on a network.
1. Bus Topology
Bus Topology is generally used with Ethernet networks. A bus topology can be both physical and
logical.This topology is probable the cheapest network type of all to initially setup, as only one cable is used the installation is fairly simple and economical.All the devices/nodes are connected sequentially to the same backbone or transmission line. Every computer and network devices connects to the same cable,so if the cables fails, the whole network is down,but the cost setting up the network is reasonable. The connecting cable has a limited length.This is a simple, low-cost topology, but its single point of failure presents a risk.Bus network share a common connection that extends to all devices.This network topology is used in small network, and it is simple to understand. This type of networks transfers data by passing messages through the same cable, so a break in any part of
the cable will bring the whole network down.
2.Star Topology
Star topology is the most preferred and popular model. This topology connects the devices via a centralized unit, such as a hub or switch. Every device has its own connection to the hub. If the hub fails,the network is down for all connected devices.Any device/ cable affect the rest of the network. Physically adding new devices to a Star network is very simple compared to any of the other topology. But the star topology is easy to set up and easy to troubleshoot.And the failure of individual nodes or cables does not necessarily creates downtime in the network but the failure of a central device can. The cost of setup is higher than for bus and ring network topology. star topology are commonly mixed with one of the other topology to create a hybrid topology.
3.Ring Topology
All network devices are connected sequentially to backbone as in bus topology except that the backbone ends at the starting node, forming a ring. Each device in a ring network is attached to two other devices, and the last device connects to the first to form a circular network. Data is passed one way from device to device. Adding new device to an existing physical ring network can be complicated, as any new device needs to go in between the existing devices.
4.Tree topology
A root node is connected to two or more sub-level nodes, which themselves are connected hierarchically to sub-level nodes. It integrates the star and bus topology in a hybrid approach to improve network scalability. The network backbone may have a bus topology, while the low-level nodes connect using star topology.
5.Mesh Topology
The topology in each node is directly connected to some or all the other nodes present in the network. This redundancy makes the network highly fault tolerant but the escalated costs may limit this topology to highly critical networks. Robust and troubleshooting is relatively easy. Installation and configuration are more complicated than star, bus and ring topology. In a mesh topology, each PC is connected to every other PC in the network by its own cable.The amount of cables need for a mesh network can be calculated by:
CN=(D*(D-1))/2
CN:Cables Needed
D:Amount of devices on the Network.
6.Wireless Topology
Wireless network is a new type of network topology.Wireless networks are slower than wired networks.With the generation of laptops and mobile devices,the need for networks to accommodate wireless remote access has increased vastly.
Physical Topology
When in the context of networking, refers to the physical layout of the devices
connected to the network, including the location and cable installation.
Logical Topology
Defines how the hosts access the media to send data. Shows the flow of data on a network.
1. Bus Topology
Bus Topology is generally used with Ethernet networks. A bus topology can be both physical and
logical.This topology is probable the cheapest network type of all to initially setup, as only one cable is used the installation is fairly simple and economical.All the devices/nodes are connected sequentially to the same backbone or transmission line. Every computer and network devices connects to the same cable,so if the cables fails, the whole network is down,but the cost setting up the network is reasonable. The connecting cable has a limited length.This is a simple, low-cost topology, but its single point of failure presents a risk.Bus network share a common connection that extends to all devices.This network topology is used in small network, and it is simple to understand. This type of networks transfers data by passing messages through the same cable, so a break in any part of
the cable will bring the whole network down.
2.Star Topology
Star topology is the most preferred and popular model. This topology connects the devices via a centralized unit, such as a hub or switch. Every device has its own connection to the hub. If the hub fails,the network is down for all connected devices.Any device/ cable affect the rest of the network. Physically adding new devices to a Star network is very simple compared to any of the other topology. But the star topology is easy to set up and easy to troubleshoot.And the failure of individual nodes or cables does not necessarily creates downtime in the network but the failure of a central device can. The cost of setup is higher than for bus and ring network topology. star topology are commonly mixed with one of the other topology to create a hybrid topology.
3.Ring Topology
All network devices are connected sequentially to backbone as in bus topology except that the backbone ends at the starting node, forming a ring. Each device in a ring network is attached to two other devices, and the last device connects to the first to form a circular network. Data is passed one way from device to device. Adding new device to an existing physical ring network can be complicated, as any new device needs to go in between the existing devices.
4.Tree topology
A root node is connected to two or more sub-level nodes, which themselves are connected hierarchically to sub-level nodes. It integrates the star and bus topology in a hybrid approach to improve network scalability. The network backbone may have a bus topology, while the low-level nodes connect using star topology.
5.Mesh Topology
The topology in each node is directly connected to some or all the other nodes present in the network. This redundancy makes the network highly fault tolerant but the escalated costs may limit this topology to highly critical networks. Robust and troubleshooting is relatively easy. Installation and configuration are more complicated than star, bus and ring topology. In a mesh topology, each PC is connected to every other PC in the network by its own cable.The amount of cables need for a mesh network can be calculated by:
CN=(D*(D-1))/2
CN:Cables Needed
D:Amount of devices on the Network.
6.Wireless Topology
Wireless network is a new type of network topology.Wireless networks are slower than wired networks.With the generation of laptops and mobile devices,the need for networks to accommodate wireless remote access has increased vastly.
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