LANs and WANs
What is a network?
A network is two or more computers connected together so they can share data and resources: files, printers, and an internet connection.
| LAN (local area network) | WAN (wide area network) | |
|---|---|---|
| Area | A small area on one site, such as a home, school or office | A large geographical area: across towns, countries or the world |
| Hardware | Usually owned by the organisation that uses it | Often uses cables, phone lines and satellites owned by telecoms companies and rented |
| Examples | A school's network; a home Wi-Fi network | A bank connecting its branches' LANs; the internet, the biggest WAN of all |
A WAN usually connects LANs together.
Key terms
What affects network performance?
A network's performance is how quickly and reliably it moves data. It depends on:
- Bandwidth: the amount of data that can be sent each second, measured in bits per second, such as megabits per second (Mbps). More bandwidth means faster transfers.
- The number of devices: devices share the bandwidth, so the more that are sending data at once, the slower it gets for each.
- The amount of traffic: streaming video or downloading big files uses much more bandwidth than sending emails.
- The transmission media: a wired connection is usually faster than a wireless one, and fibre-optic cable faster than copper.
- Wireless signal strength: walls, distance and interference from other devices weaken Wi-Fi signals, so data has to be sent again.
Key terms
Client–server networks
In a client–server network, one or more servers provide services, and the other computers, the clients, request them. A server might store files, send web pages, handle email or manage printing.
Advantages:
- Files, user accounts, security and backups are all managed in one place, by a network manager.
- Users can log in and get their files from any client.
Disadvantages:
- Servers are expensive, and need specialist staff to run them.
- If a server fails, its clients lose its services.
- A server can slow down when too many clients make requests at once.
Key terms
Peer-to-peer networks
In a peer-to-peer network, there's no central server: every computer is equal, and each one shares its own files and resources directly with the others. A small home network often works like this.
| Client–server | Peer-to-peer | |
|---|---|---|
| Cost | Expensive: servers and staff | Cheap, and easy to set up |
| Management | Central: one place for backups, security and accounts | Each user looks after their own computer and backups |
| If one computer fails | If the server fails, everyone is affected | Only that computer's files are lost to the others |
| Speed | Can slow if the server is busy | A peer slows down while others use its files |
Exam tip
In a scenario question, recommend one and give reasons linked to the scenario: a small family needs cheap and simple; a school needs central backups and security.