Local Area Networks

Network

A network is a group of interconnected devices that communicate and share resources with each other.

Network Topologies

Devices (or stations) can be connected in different ways to form a network. Each has its own advantages and disadvantages. The appropriate topology must be chosen based on the requirements such as:

• cost
• reliablity
• expandability
• performance

Bus Topology

All devices are connected to a single cable, known as bus. The bus acts as a shared communication channel. Supports full duplex communication. Simple and easy to implement. Can be difficult to troubleshoot and maintain.

Stations tap into the bus. Terminators absorb reflections and prevent signal degradation.

Tree Topology

An extension to the bus topology. Devices are connected to a bus. There will be multiple buses, each with its own terminator. All buses will connect to the headend.

Note

In bus and tree topologies, there are 2 problems:

• Indicating whom the communication is intended to
• When to access the shared medium

And they are solved by:

• Data sent as frames with control information in header – Media access control protocols

Ring Topology

A set of repeaters joined with point-to-point links in a closed loop. Unidirectional transmission by repeaters. Each station is attached to the network at a repeater.

Data transmitted as frames. Destination recognizes and reads data. Removed at source after full circulation.

Star Topology

One station is a logical communication center. Works as broadcast (hub) or frame-switching device (switch). All communication passes through the central station.