Computer Networks: Types, Topologies, and Devices

Posted on Sep 12, 2024 in Computers

Computer Networks

A network is a set of interconnected computers that can communicate by sharing data and resources regardless of the physical location of the various devices. Through a network, processes can be run on another computer, files can be accessed, messages can be sent, and programs can be shared. The computers are usually connected by cables. However, if the company covers a large area, the connections can be made through telephone lines, microwaves, fiber optic lines, and even satellites.

Every active device connected to the network is called a node. An active device is one that intervenes in communication independently, without being controlled by another device. For example, certain printers are autonomous and can provide service on a network without a computer connected to handle them; these printers are network nodes.

Types of Networks

Depending on the territory covered by a network, they are classified as:

  • LAN: Local Area Network. It consists of a set of interconnected stand-alone computers that can communicate and share resources. They cover a relatively small area, such as a building or campus.
  • WAN: Wide Area Network. These networks include larger regions and can even span multiple countries. LANs can be connected to form a WAN.

Characteristics of a Local Area Network (LAN)

There are many types of local networks, but they have common characteristics:

  1. Common Communication Means: All devices can share information, software, and hardware through a common communication medium, regardless of the physical location of the user or device. Local loops are contained in a small physical area, such as a building or campus.
  2. High Transmission Speed: LANs offer a very high transmission speed to adapt to the needs of users and equipment. The equipment on the local network can transmit data at the maximum speed at which stations can communicate with the network, usually one Mb per second.
  3. Short Distance: The distance between stations is relatively short, ranging from a few meters to several kilometers.
  4. Standard Cables: LANs allow the use of standard connection cables.
  5. Device Communication: All devices can communicate with the rest, and some of them can function independently.
  6. Reliable System: LANs are reliable systems with a very low error rate. They normally have their own system for detecting and correcting transmission errors.

Network Topologies

Bus Network

The bus topology is a simple design where a single cable, known as the “bus,” is shared by all devices on the network. The cable goes through each computer and has an end at each of the two extremes. The devices are typically connected to the bus using a T-connector.

Advantages:

  • Simplicity
  • Economy

Drawbacks:

  • If the cable fails at any point, the whole network stops working.
  • Troubleshooting can be difficult in large networks.

Star Network

In a star network, nodes are connected by dedicated cables to a central point called a hub or switch. Each workstation has its own dedicated cable, making it suitable for longer cable lengths.

Advantages:

  • Easy detection of wiring problems
  • High fault resistance (a cable problem only affects the connected user)

Ring Network

In a ring network, nodes are connected in a closed circle. The ring is unidirectional, meaning data packets circulate in one direction only. In a simple ring LAN, a cable cut affects all stations. Therefore, systems have been developed with double rings or combinations of ring and star topologies.

Example:

Ethernet networks using coaxial cable follow a linear bus topology, both physically and logically. However, when using two-wire cable, the logical topology remains a bus, but the physical topology becomes a star or distributed star.

Network Devices

Router or Gateway

A router is a device connected to the network that links different networks. Its functions include:

  • Adapting the structure of information from one network to another (datagrams with different sizes and structures)
  • Passing information from one hardware to another (different speeds and hardware)
  • Routing information through the optimal route
  • Bringing together information coming from different routes

Bridge

A bridge merges two different logical segments of the same physical network. In other words, it divides a network into two logical subnets. The use of a bridge isolates unnecessary data traffic between segments, reducing collisions.

Repeater

A repeater amplifies the signal, allowing the use of longer cable lengths.