# Define computer network. Discuss the types of network topologies with their pros and cons.

A computer network is a group of computers linked to each other that enables the computer to communicate with another computer and share its resources, data, and applications.

Network Topology is the schematic description of a network arrangement, connecting various nodes(sender and receiver) through lines of connection.

Types of Network Topology:

1. Bus Topology
2. Ring Topology
3. Star Topology
4. Mesh Topology
5. Tree Topology
6. Hybrid Topology

### 1. Bus Topology:

Bus topology is a network type in which every computer and network device is connected to a single cable. When it has exactly two endpoints, then it is called Linear Bus topology.

1. It is cost-effective.
2. The cable required is the least compared to other network topologies.
3. Used in small networks.
4. It is easy to understand.
5. Easy to expand joining two cables together.

1. Cables fail then the whole network fails.
2. If network traffic is heavy or nodes are more the performance of the network decreases.
3. The cable has a limited length.
4. It is slower than the ring topology.

### 2. Ring Topology:

It is called ring topology because it forms a ring as each computer is connected to another computer, with the last one connected to the first. Exactly two neighbors for each device.

1. The transmitting network is not affected by high traffic or by adding more nodes, as only the nodes having tokens can transmit data.
2. Cheap to install and expand

1. Troubleshooting is difficult in a ring topology.
2. Adding or deleting the computers disturbs the network activity.
3. Failure of one computer disturbs the whole network.

### 3. Star Topology:

In this type of topology, all the computers are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node.

1. Fast performance with few nodes and low network traffic.
2. Hub can be upgraded easily.
3. Easy to troubleshoot.
4. Easy to set up and modify.
5. Only the node affected which has failed, the rest of the nodes can work smoothly.

1. The cost of installation is high.
2. Expensive to use.
3. If the hub fails then the whole network is stopped because all the nodes depend on the hub.
4. Performance is based on the hub that is it depends on its capacity.

### 4. Mesh Topology:

It is a point-to-point connection to other nodes or devices. All the network nodes are connected to each other. Mesh has n(n-1)/2 physical channels to link n devices.

There are two techniques to transmit data over the Mesh topology, they are :

1. Routing
2. Flooding

1. Each connection can carry its own data load.
2. It is robust.
3. The fault is diagnosed easily.
4. Provides security and privacy.

1. Installation and configuration are difficult.
2. The cabling cost is more.
3. Bulk wiring is required.

### 5. Tree Topology:

It has a root node and all other nodes are connected to it forming a hierarchy. It is also called hierarchical topology. It should at least have three levels to the hierarchy.

1. Extension of bus and star topologies.
2. The expansion of nodes is possible and easy.
3. Easily managed and maintained.
4. Error detection is easily done.

1. Heavily cabled.
2. Costly.
3. If more nodes are added maintenance is difficult.
4. The central hub fails, and the network fails.

### 6. Hybrid Topology:

It is two different types of topologies which is a mixture of two or more topologies. For example, if in an office in one department ring topology is used and in another star topology is used, connecting these topologies will result in Hybrid Topology (ring topology and star topology).

1. Reliable as Error detecting and troubleshooting is easy.
2. Effective.
3. Scalable as size can be increased easily.
4. Flexible.