Network Topology

Network Topology

A network topology is the arrangement of nodes in a computer network that enables them to communicate. It can be considered in two ways:

• Physical topology: The physical placement of devices and cables.
• Logical topology: How data flows between devices, regardless of their physical locations.

The lesson covers five common topologies: bus, ring, star, mesh, and hybrid.

1. Bus Topology

All nodes connect to a shared transmission medium. When a node sends data, the signal travels along the medium and is received by all nodes. The intended recipient accepts it; the others reject it. Data can flow in both directions along the medium.

Advantages

• Inexpensive because it uses a single main cable.
• Suitable for temporary networks.
• Failure of an individual node does not necessarily affect other nodes.

Disadvantages

• Failure of the shared cable can bring down the network.
• A break can prevent communication between devices on opposite sides of it.
• Cable length is limited.
• All nodes receive the transmitted signal, which the lesson identifies as a security drawback.

2. Ring Topology

Nodes form a closed loop, with each node connected to its two nearest neighbors. Nodes are peers with equal access. Data moves in one direction around the ring, passing through intermediate nodes before reaching its destination.

A token controls access to transmit: the node holding the token gets a turn to send data, then passes the token around the ring.

Advantages

• The lesson describes its performance as better than bus topology.
• Nodes have equal access to the opportunity to transmit.

Disadvantages

• Communication is unidirectional, so data may need to pass through several nodes.
• A node or link failure can disrupt the ring.
• A weak link can become a bottleneck.
• Heavy traffic can degrade performance.
• Data passes through intermediary nodes, which the lesson presents as a security concern.

3. Star Topology

Each node connects to a central device, such as a hub or switch. All traffic passes through this device, which forwards data toward its destination.

Advantages

• Easy to design and implement.
• Provides centralized administration.
• Can be expanded by adding devices or connecting additional star networks, for example, through another switch or a repeater.

Disadvantages

• Failure of the central hub or switch stops communication across the network.
• An overloaded central device can become a bottleneck.
• The central device adds cost.

4. Mesh Topology

In the fully connected mesh described, each node has a direct link to every other node. Multiple paths can allow data to reach its destination even if a link fails.

Advantages

• Offers strong fault tolerance and reliability because alternative paths may be available.

Disadvantages

• Requires many links and is expensive.
• Broadcasting can create complications as messages are forwarded through the network.
• It may suit smaller networks, but the lesson describes it as impractical for very large networks, such as those with thousands of computers.

5. Hybrid Topology

A hybrid topology combines two or more different topologies. The example in the video combines bus, star, and mesh arrangements in one network.

Speaker

The sole speaker in the subtitles is a Neso Academy instructor, presenting the lesson.