# What is a network?

A network refers to a collection of devices. These include computers, servers, printers, and smartphones. The devices link together to allow communication. 

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<mark style="color:blue;">**Types of networks**</mark>

There are different types of networks, each with different characteristics and areas of use. The main types of networks are:

1. **LAN** (Local Area Network)

   A LAN is a network that connects devices within a limited area, such as a home, office, or building. It is fast and usually private.
2. **WLAN** (Wireless Local Area Network)

   A WLAN is a wireless LAN, where devices join through Wi-Fi or similar wireless methods. Flexibility increases notably here. No need arises for running physical wires everywhere.
3. **WAN** (Wide Area Network)

   A WAN covers a large geographical area, such as cities, countries, or continents. It often uses public infrastructure such as the Internet.
4. **MAN** (Metropolitan Area Network)

   A MAN covers an entire city or metropolitan area, larger than a LAN but smaller than a WAN.
5. **PAN** (Personal Area Network)

   A PAN is a network for personal devices, usually within a few meters of each other. For example, connecting a smartphone to a laptop via Bluetooth.

<mark style="color:blue;">**Network Topologies**</mark>

The topology of a network describes how the devices are connected to each other. The most common layouts are:

* **Star Topology:** All devices are connected to a central hub, such as a switch. Its popularity makes it the preferred choice nowadays. Its reliability is evident. The failure of a single cable only affects the connected device.

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* **Bus Topology:** All devices rely on a single main cable for all connections. Simplicity defines it. However, a break in that central line shuts everything down.

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* **Ring Topology:** Each device hooks to two neighbors. Data flows in a single direction around the circle. One faulty link disrupts the entire flow.

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* **Mesh Topology:** Each device connects directly to all the others. Reliability is high. However, costs increase significantly. Configuration also becomes more complicated.

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* **Tree Topology:**&#x54;he tree topology combines elements of the star and bus models. Star groups are connected to a backbone bus cable. Scalability is high. It is particularly suitable for large environments, such as university campuses or corporate headquarters.

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* **Hybrid Topology:** Hybrid topology combines multiple styles. For example, a ring backbone can connect several star sections. Tailor-made solutions are developed for large, complex systems.

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<mark style="color:blue;">**Network devices**</mark>

Devices play a fundamental role in the creation and management of networks. Each one has a specific role:

* **Router** → Routers play a central role in connecting separate networks. For example, a home setup connects to the internet via a router. Data packets are routed through optimal paths. Decisions depend on IP addresses. Many models now include extra features. Built-in firewalls ensure security. Wireless points enable Wi-Fi. Small switches manage wired connections.
* **Switch** → Switches connect devices within a single LAN. More intelligent than hubs, they direct data to the right place. This keeps traffic flowing smoothly. Efficiency increases in both home and business use. MAC addresses guide the process.
* **Hub** → Hubs are an outdated option. They connect devices but transmit data to everyone. Unnecessary traffic accumulates. As a result, speed decreases. Switches have taken over in current configurations.
* **Access Point (AP)** → Access points extend wired networks wirelessly. Laptops and phones connect without cables. Coverage extends into homes, offices, schools and open areas.
* **Firewall** → Firewalls monitor incoming and outgoing traffic. Rules filter out threats. Unauthorised access is blocked. Basic versions are integrated into routers. Dedicated hardware offers more in-depth protection, particularly for businesses.
* **Modem** → Modems act as a bridge to the internet. They convert digital signals into analogue signals and vice versa. Telephone lines, DSL, cable or fibre optic lines carry the load. Modems are often combined with routers in domestic units. A single device then supervises the connection and local traffic.
* **Gateway** → Gateways translate between incompatible protocols. Networks with different ‘languages’ communicate seamlessly. Enterprise configurations, IoT groups, and technology combinations rely on them.
* **Bridge** → Bridges connect separate LANs into a single, larger unit. They forward traffic only when necessary. Layer two operations define how they work. Their functions are now mainly integrated into switches and routers.
* **Repeater** → Repeaters amplify weak signals. The range extends to difficult spots. They are useful in large buildings or areas full of obstacles. They are often used to improve Wi-Fi.

| Device       | Main function                                                           |
| ------------ | ----------------------------------------------------------------------- |
| Router       | Connects different networks and directs data traffic                    |
| Switch       | Connects devices in a LAN, sending data only to the correct destination |
| Hub          | Connects devices but sends data to all, creating unnecessary traffic    |
| Access Point | Provides wireless connectivity to a wired network                       |
| Firewall     | Filters and protects network traffic from unauthorized access           |
| Modem        | Converts signals to connect a network to the Internet                   |
| Gateway      | Translates between networks using different protocols                   |
| Bridge       | Connects two LANs, extending communication                              |
| Repeater     | Amplifies and extends network signals                                   |