Basic Concepts of Computer Networks : Network Topology

In networking terms, the structure you are planning to connect the computers to, is called network topology.

Network topology is also referred to as the configuration of a network.

It usually refers to the physical arrangement of the computers and other networking devices that are linked together.

It defines how nodes are connected to one another in a communication network. A network topology must show the nodes and the links between them. The nodes must be an active device connected to the network, such as a computer, printer, hub or a router.

There are three main types of network topology. They are :

1. bus topology,
2. star topology and 
3. ring topology.

BUS TOPOLOGY 

Bus networks are very common in Local Area Networks (LAN). A bus network must have a common backbone (the central cable) to connect all devices.

All nodes share the backbone to communicate with each other on the network. Sometimes, a bus network has more than one server. Sometimes, a server is not needed on the network.

ADVANTAGES OF BUS TOPOLOGY

• Easy implementation. New devices can be added to the backbone or to the existing nodes.
• Failure of a node doesn't affect the entire LAN.
• No disruptions to the network when connecting or removing devices.
• Network can easily be extended, by adding new devices to the backbone or existing nodes.

DISADVANTAGES OF BUS TOPOLOGY

• If the backbone fails, the entire bus network will be affected.
• Network speed decreases when the number of nodes increases.
• Troubleshooting is difficult when one of the nodes fails.

RING TOPOLOGY

 A ring topology consists of all computers and other devices that are connected in a loop. Ring topology is also known as a ring network.

A ring network can be found in Local Area Networks. In a ring network each node 

directly connect to two neighbouring nodes.

A server may exist in a ring network, but it will not connect to all the nodes in the network.

The server, like other nodes, will only communicate to its two neighbouring nodes.

ADVANTAGES OF A RING TOPOLOGY

• Troubleshooting is easy when one of the nodes fails.
• Repair or remove the failing nodes and the network will continue to function.

DISADVANTAGES OF A RING TOPOLOGY

• Implementation is difficult. Network administrator has to terminate the entire network to install a new node between existing nodes.
• A failing node will affect the entire LAN.
• Connecting or removing devices is difficult because network administrator needs to terminate the network in order to do it.
• Network speed decreases when the number of nodes increases.

STAR TOPOLOGY

In the early days of computer networking, all computers were connected to a centralised mainframe computer.

All resources and management of information were centred in this main computer.

The idea of a centralised mainframe computer is where the basic concept of a star topology comes from.

A star topology consists of a central host which acts as the centre, and all nodes connect to the host. A star topology is also known as star network.

• A star network is found in a Local Area Network setting.
• A star network must have a host which acts as the centre.
• The host can be a server, hub or router.
• In a star network, every node will not connect to the neighbouring nodes.
• Every node must connect to the host in order to communicate.
• The host will control the flow of communication in the network.

ADVANTAGES AND DISADVANTAGES OF STAR TOPOLOGY

Advantages

• It is easy to implement. You only add nodes to the host.
• The failure of a node does not affect the entire LAN.
• There are no disruptions to the network when connecting or removing devices.
• The network can be extended by adding new devices to the host or nodes.
• Troubleshooting is easy when the host fails. Simply repair or replace the host and the network will continue to function.

Disadvantages

• If the host fails, the entire LAN will be affected.
• Network speed decreases when the number of nodes increases.
• Troubleshooting is difficult when one of the nodes fails.
• A host must be installed to control the network.

DIFFERENCES OF NETWORK TOPOLOGIES

	Bus Topology	Ring Topology	Star Topology
Structure	there is a single central cable (backbone) and all computers and other devices connect to it	all computers and other devices are connected in a circle	there is a central host and all nodes connect to it
Host existence	depends on network needs	depends on network needs	yes
Connection between nodes	It has no connection between the nodes.	yes	no
Host failure	network can still run	network will fail	network will fail
Node failure	network can still run	network will fail	network can still run
Ease of troubleshooting	Difficult. Need to search for the problematic node one by one	Depends on backbone. If there is a backbone, troubleshooting is difficult. If there is no backbone, the focus is on the two nodes not communicating	Depends on the host. Itis easier to repair the problematic host. However, if the nodes fail, then each node has to be searched
Ease of adding or removing nodes	easy	difficult	average
Number of nodes when extending network	many	limited	limited

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Others Lesson : | click lesson to view |

• Definition
• Types of Networks
• Network Architecture
• Network Topology
• Protocol
• Internet, Intranet, Extranet