What is topology?

What is topology?

Simply, the way in which connections are made is called as topology of network.

Topology is predefined protocol for managing computers in the network.

Types of topologies

1.Mesh Topology

fig. Mesh Topology

In mesh topology each device has dedicated connection to each computer in network. Mesh topology is fastest topology.because it has dedicated connection to devices.The number of cables required to implement mesh topology can be obtained by following formula.In case , if any device fails that doesn’t affect on entire network.

Practical example of Mesh : Each regional telephone office connected to another by dedicated links.

Number of cables=n(n-1)
Where n=number of devices.

Advantages of Mesh topology

  1. This is Fastest topology.
  2. It is robust. if any cable/ device fails , that will not affect on entire network
  3. Security. When we have dedicated line the message travels only in between sender and receiver.
  4. fault identification and isolation is easy.
  5. traffic can be routed in case of cable failure

Disadvantages of Mesh Topology

  1. High amount cabling is required.
  2. costly, as we required high amount of cabling.
  3. Installation and re-connection is very difficult.

2.Star Topology

fig. Star Topology

In star topology each device has dedicated connection to only central hub. Each data transfer completed using central hub. No device is connected to each other directly. The hub acts as exchange. If device want to send data to another , it sends data to hub and hub sends it to destination. star doesn’t allow traffic between devices

Advantages of star topology

  1. Less expensive than Mesh topology.
  2. Unlike mesh, only one I/O port required in device.
  3. if link fails, this only affect respective device and not on others

disadvantages of star topology

  1. Whole network is dependent on hub. In case of hub failure it results in whole network failure
  2. although , it requires less cabling than mesh but as we require each device with dedicated link to hub , it requires more cabling than other topologies.

3. Ring Topology

fig. Ring topology

in ring topology device has only connection with only devices either of sides. Rings can be unidirectional, with all traffic travelling either clockwise or anticlockwise around the ring, or bidirectional.

Advantages of Ring topology

  1. Easy to install and re-configure.
  2. To add new device or to remove a device we just need to change two connections.
  3. Fault isolation in simplified.

Disadvantages of Ring topology

  1. Unidirectional traffic can be disadvantages sometimes.
  2. break in the ring disables whole network.

4.Bus topology

fig. bus topology

In bus topology the nodes are connected to the bus cable by drop lines and taps. the backbone cable is main cable where each device is connected.A tap is connector between the devices and main cable.In case of backbone cable failure the whole network fails.  traffic generated by each station has equal transmission priority

Advantages of bus topology

  1. Works well in small networks.
  2. easiest topology configuration.
  3. less cabling than star topology.
  4. Linear in fashion.

Disadvantages of bus topology

  1. Difficult identify problems
  2. in case of backbone cable failure will result in whole network failure or splits into two.
  3. terminators are required at both ends.
  4. Not good for big networks.

5.Tree topology

fig. Tree topology

Tree topology has hierarchy of devices as tree. thats why its known as tree topology

In computer networks, a tree topology is also known as a star bus topology. It incorporates elements of both a bus topology and a star topology. Below is an example network diagram of a tree topology, in which the central nodes of two star networks are connected to one another.

Advantages of tree topology

  1. Node expansion is fast and easy.
  2. Detection of error is an easy process
  3. Failure of one node never affects the rest of the network.
  4. It is easy to manage and maintain

Disadvantages of tree topology

  1. If more nodes are added, then its maintenance is difficult
  2. If the hub or concentrator fails, attached nodes are also disabled.
  3. It is heavily cabled topology

6.Hybrid Topology

fig. hybrid topology.

Hybrid topology is an integration of two or more different topologies to form
a resultant topology which has many advantages (as well as disadvantages) of all the constituent basic topologies rather than having characteristics of
one specific topology. This combination of topologies is done according to the
requirements of the organization.

Advantages of hybrid topology

  1. Reliable: Unlike other networks, fault detection and troubleshooting is easy in this type of topology.
  2. Scalable: It is easy to increase the size of network by adding new components, without disturbing existing architecture.
  3. Hybrid Network can be designed according to the requirements of the organization and by optimizing the available resources.

Disadvantages of Hybrid topology

  1. Main problem with this topology is its design. because it’s very complex to design this topology.
  2. Hubs used to connect networks are expensive
  3. Costly and complex on big network.

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