## Definition of network topology

Network topology refers to the way in which the nodes of a network are linked together. It determines the data paths which, used between any pair of nodes in the network. Some of the network topologies are as follows:

### Types of network topology:

• Star topology
• Ring topology
• Bus topology
• Tree topology
• Mesh topology

### 1. Star topology

In the star topology, each device connected to point-to-point only to central controller usually called HUB. In this topology, if a device wants to send data to another, at first it sends the data to the central controller then it relays the data to other connected devices.

#### Some advantages (merits) and disadvantages (demerits) of star network topology as follows:

• Less cabling required.
• Less expensive.
• Easy to install and re-configuration.
• If one node fails due to some reason it does not affect the entire network.

• If the central HUB fails then the whole network fails to operate.

### 2. Ring topology

In-ring topology there is no central controller or HUB. In this topology, a signal is passed along the ring in one direction from device to device (or node to node) until it reaches its destination.

• No central controller is necessary.
• Required cable is less.
• Inexpensive.

• The data travels in only one direction from node to node around the ring.
• If a link is a failure the entire networks are also failing.

### 3. Bus network topology

A bus topology is a multi-point topology. One long cable act as a backbone to link all the devices in the network. Computers are connected to the bus by drop lines and taps. A drop line is a connection running between the devices and the main cable. A tap is a connector to connect devices to the main cable. At both ends of the cable, terminators are used. In this topology, the message travels in both direction of cable.

• Easy to set up.
• Required cable is less.
• One node failure does not affect the entire network.
• Inexpensive.

• Data traffic is high. Hence, the collision rate is also high.
• A break in the bus cable stops all transmission.

### 4. Tree topology

The tree topology a widely used approach in data communication. It is similar to bus topology except that the transmission lines are divided into several wires. Advantages and disadvantages are the same as bus topology. or it also written below,

• Easy to set up.
• Required cable is less.
• One node failure does not affect the entire network.

• Data traffic is high.
• A break in the bus cable stops all transmission.

### 5. Mesh topology

In a mesh topology, each station is connected to every station in the network. It is used in a network, that does not have a large number of nodes involved.

• Very fast data communication due to full connectivity.
• If one link becomes unavailable, it does not affect the entire network.

• Installation and re-configuration are difficult.
• The required huge amount of cabling. Hence, it is expensive.
• Fault isolation is difficult.