What is topology? explain types of topology with diagram and advantages and disadvantages.

 Solution:-

Topology

Geometric representation of how the computers are connected to each other is known as topology. 

There are five types of topology – Bus, Star, Mesh, Ring and Hybrid.

• Bus Topology 

•  Bus topology is a network setup in which each computer and network device are connected to a single cable or backbone by the help of interface connectors. This central  cable is the backbone of the network and is known as Bus. 

•  Every workstation  communicates with the other device through this Bus. A signal from the source is  broadcasted and it travels to all workstations connected to bus cable. 

•  Although the  message is broadcasted but only the intended recipient, whose MAC address or IP  address matches, accepts it. If the MAC /IP address of machine doesn’t match with the  intended address, machine discards the signal. 

•  A terminator is added at ends of the  central cable, to prevent bouncing of signals. A barrel connector can be used to extend it.

Advantages of Bus topology

1. It is easy to set-up and extend bus network.

2. Cable length required for this topology is the least compared to other networks.

3. Bus topology costs very less.

4. Linear Bus network is mostly used in small networks which are good for LAN.

Disadvantages of Bus Topology

1. Difficult to identify the problems if the whole network goes down.

2. It can be hard to troubleshoot individual device issues.

3. Not great for large networks. 

4. Terminators are required for both ends of the main cable.

5. Additional devices slow the network down.

6. If a main cable is damaged, the network fails or splits into two.

• Star Topology

•  In a star topology, each device has a dedicated point-to-point link only to a central controller, usually called a hub.  

•  The devices are not directly linked to one another.

•  A star topology does not allow direct traffic between devices.

•  The controller acts as an exchange.

•   If one device wants to send data to another, it sends the data to the controller, which then relays the data to the other connected device. 

•  A star topology is less expensive than a mesh topology.

•  In a star, each device needs only one link and one I/O port to connect it to any number of others. This factor also makes it easy to install and Reconfigure.

•  As long as the hub is working, it can be used to monitor link problems and bypass defective links. 

•  The star topology is used in local-area networks (LANs). High-speed LANs often use a star topology with a central hub.

Advantages of star topology:

1. Centralized management allows better monitoring the network  

2. Easy to manage as connection of nodes and removing can be done easily, without  affecting the network. 

3. Failure of one link doesn’t affect the rest of the network.

4. Easy to detect the failure and troubleshoot.

5. Better performance as the signal sent by the node doesn’t necessarily get transmitted to all workstations.

6. Easier to install

7. Less amount of cables required because each device needs to be connected with the hub only.

Disadvantages of Star Topology

1. a star topology is the dependency of the whole topology on one single point, the hub. If the hub goes down, the whole system is dead.  

2. If hub goes down everything goes down, none of the devices can work without hub.

3. Hub requires more resources and regular maintenance because it is the central system of star topology.

• Mesh Topology

•  In mesh topology each device is connected to every other device on the network through a dedicated point-to-point link.

•  When we say dedicated it means that the link only carries data for the two connected devices only. Lets say we have n devices in the network then each device must be connected with (n-1) devices of the network. Number of links in a mesh topology of n devices would be n(n-1)/2.

Advantages of Mesh Topology:

1. Avoids traffic problem

2. Robust topology since if one node fails, it does not affect the other nodes. 

3. Point to point connection makes it easier to detect errors.

4. More security and Privacy in connections.

Disadvantages of Mesh Topology:

1. More cables are required than other topologies.

2. Cost of the network is high since more number of cables are used.

3. Installation and re-configuration is difficult.

4. Setup and maintenance of the topology is difficult.

5. Through put and transmission quantity depends on media and capacity of switching nodes. 

• Ring Topology

•  In ring topology each device is connected with the two devices on either side of it. 

•  There are two dedicated point to point links a device has with the devices on the either side of it. This structure forms a ring thus it is known as ring topology.

•  If a device wants to send data to another device then it sends the data in one direction, each device in ring topology has a repeater, if the received data is intended for other device then repeater forwards this data until the intended device receives it.

Advantages of Ring Topology

1. Easy to install.

2. Managing is easier as to add or remove a device from the topology only two links are required to be changed.

Disadvantages of Ring Topology

1. A link failure can fail the entire network as the signal will not travel forward due to failure.

2. Data traffic issues, since all the data is circulating in a ring.

• Hybrid Topology

•  A combination of two or more topology is known as hybrid topology. For example a combination of star and mesh topology is known as hybrid topology.

Advantages of Hybrid topology

1. We can choose the topology based on the requirement for example, scalability is our concern then we can use star topology instead of bus technology.

2. Scalable as we can further connect other computer networks with the existing networks with different topologies.

3.It is also reliable, flexible, Effective

Disadvantages of Hybrid topology

1. Fault detection is difficult.

2. Installation is difficult.

3. Design is complex so maintenance is high thus expensive.