Primary Network Topologies

Network Topologies describe the physical or logical arrangement of nodes (devices) and their connections within a network. They define how devices are interconnected and communicate with each other.

Factors affecting Network Topologies:

• Scalability:

The ability to expand the network easily influences the choice of topology. For example, star and tree topologies are more scalable because additional devices can be added without disrupting the existing network. In contrast, bus topologies can become problematic as the number of devices increases, potentially leading to congestion and performance issues.

• Performance:

The efficiency and speed of data transmission can vary with topology. Star topologies typically offer better performance because each device has a dedicated connection to the central hub, reducing the risk of data collisions. In contrast, bus and ring topologies can suffer from performance degradation as the number of devices increases, due to increased traffic or potential bottlenecks.

• Fault Tolerance:

The network’s ability to withstand and recover from failures is critical. Mesh topologies provide high fault tolerance as they offer multiple paths for data transmission, ensuring that if one path fails, others can take over. Conversely, bus topologies are less fault-tolerant because a failure in the central cable can disrupt the entire network.

• Cost:

The cost of implementing and maintaining the network is a significant factor. Bus topologies are generally less expensive due to fewer cables and simpler setup. Star topologies may have higher costs due to the need for a central hub or switch, and mesh topologies are often the most costly due to the extensive cabling and hardware required for full connectivity.

• Ease of Installation and Maintenance:

Some topologies are easier to install and maintain than others. Star topologies are straightforward to set up and manage because issues can be isolated to individual connections without affecting the entire network. In contrast, ring and mesh topologies can be more complex, with maintenance requiring careful attention to avoid network-wide disruptions.

• Network Traffic:

The amount and type of network traffic influence topology selection. Star and mesh topologies handle high traffic volumes better due to their multiple connections and paths. Bus and ring topologies can struggle with high traffic as they rely on fewer pathways for data transfer, leading to potential congestion.

• Security:

The level of network security required can affect the choice of topology. Mesh topologies offer higher security as they provide multiple pathways and reduce the risk of single points of failure. Star topologies also offer reasonable security by centralizing network management, while bus topologies may have vulnerabilities due to the single central cable that can be a target for attacks.

Bus Topology

Data network with bus topology has a linear transmission cable, usually coaxial, to which many network devices and workstations are attached along the length. Server is at one end of the bus. When a workstation has to send data, it transmits packets with destination address in its header along the bus.

The data travels in both the directions along the bus. When the destination terminal sees the data, it copies it to the local disk.

Advantages of Bus Topology

• Easy to install and maintain

• Can be extended easily

• Very reliable because of single transmission line

Disadvantages of Bus Topology

• Troubleshooting is difficult as there is no single point of control

• One faulty node can bring the whole network down

• Dumb terminals cannot be connected to the bus

Ring Topology

In ring topology each terminal is connected to exactly two nodes, giving the network a circular shape. Data travels in only one pre-determined direction.

When a terminal has to send data, it transmits it to the neighboring node which transmits it to the next one. Before further transmission data may be amplified. In this way, data raverses the network and reaches the destination node, which removes it from the network. If the data reaches the sender, it removes the data and resends it later.

Advantages of Ring Topology

• Small cable segments are needed to connect two nodes

• Ideal for optical fibres as data travels in only one direction

• Very high transmission speeds possible

Disadvantages of Ring Topology

• Failure of single node brings down the whole network

• Troubleshooting is difficult as many nodes may have to be inspected before faulty one is identified

• Difficult to remove one or more nodes while keeping the rest of the network intact

Star Topology

In star topology, server is connected to each node individually. Server is also called the central node. Any exchange of data between two nodes must take place through the server. It is the most popular topology for information and voice networks as central node can process data received from source node before sending it to the destination node.

Advantages of Star Topology

• Failure of one node does not affect the network

• Troubleshooting is easy as faulty node can be detected from central node immediately

• Simple access protocols required as one of the communicating nodes is always the central node

Disadvantages of Star Topology

• Long cables may be required to connect each node to the server

• Failure of central node brings down the whole network

Tree Topology

Tree topology has a group of star networks connected to a linear bus backbone cable. It incorporates features of both star and bus topologies. Tree topology is also called hierarchical topology.

Advantages of Tree Topology

• Existing network can be easily expanded

• Point-to-point wiring for individual segments means easier installation and maintenance

• Well suited for temporary networks

Disadvantages of Tree Topology

• Technical expertise required to configure and wire tree topology

• Failure of backbone cable brings down entire network

• Insecure network

• Maintenance difficult for large networks