A Topology of a Network is the geometric representation of the relationship of all the links & linking devices.
There are five basic LAN topologies which are: Mesh Topology, Star Topology, Bus Topology, Ring Topology, and Hybrid Topology.
1. Mesh Topology
In Mesh Topology each device has a dedicated link to every other device in the link.
Each link carries traffic only between the two devices i.e. connected by that link.
In this topology n(n+1)/2 cable required to connect ‘n’ devices i.e. in the above figures 9 cables are required to connect 6 devices.
- Each connection can carry its own data load thus eliminate the traffic problem.
- Fault identification & fault isolation becomes easy.
- Due to paint connection privacy & security.
- A large number of cables are required.
- A large number of parts are required.
- Installation & reconfiguration is difficult.
2. Star Topology
Each device has a dedicated point-to-point link only to a central controller usually called a hub.
The device is not directly linked to each other, the central device hub acts as an exchanger.
If the device wants to send data to another device it sends the data to the controller which then releases the data to another connected device.
- Less expensive than Mesh Topology.
- Easy installation.
- Easy fault identification & isolation.
- Extra Hardware is required.
- The number of devices of a Network is limited by the number of ports on the hub.
- Each device needs to be connected to a central hub
3. Tree Topology (Extended Star)
In this topology, nodes are linked to a central hub that controls the traffic to the network.
It is a modified star topology however not every device plugs directly into the control hub.
- It allows more devices to be attached to a single central hub & also increases the distance that signal can travel between devices.
4 . Bus Topology
It is a multi-point topology, one long cable acts as a backbone to link all the devices in a network.
Nodes are connected to the bus cable by drop lines & taps
In Bus topology number of taps & devices are limited & the distance between these taps is also limited.
- Easy to install.
- Less amount of Cable.
- Difficult in reconfiguration & fault isolation.
- Difficult to add new devices.
- Signal degradation at each tap.
- Break on the backbone cable stops all transmission.
5. Ring Topology
Each device has a dedicated point-to-point connection only with two devices on either side of it.
The signal is passed along in one direction from device to device units if reaches its destination.
Each device in a ring acts as a repeater.
- Easy to install & re-configure.
- Fault isolation is easy.
- Unidirectional Traffic.
- A break in a ring can disable the entire network.
- The number of devices limited by tiny length.
6. Hybrid Topology
In this topology, the network combines several topologies as Sub Network, Linked together in a large topology.
Different topologies can be connected to each other via a control controller in a star topology.