Fundamentals of Computer Networks — AQA GCSE Computer Science
A network is two or more devices connected to share data and resources. This unit covers network types, topologies, protocols and the layered model.
Types of network
- LAN (Local Area Network) — covers a small geographic area (e.g. a school or home); the infrastructure is usually owned by the organisation.
- WAN (Wide Area Network) — covers a large geographic area (e.g. the internet); often uses third-party infrastructure.
Networks can be wired (e.g. ethernet, faster and more secure) or wireless (Wi-Fi, more convenient but can be slower/less secure). Factors affecting performance include bandwidth, number of users, transmission media and interference.
Network topologies
- Star topology — all devices connect to a central switch. Reliable (one cable failing affects only one device) but needs lots of cable.
- Bus/mesh — alternative arrangements; in a mesh, devices connect to many others, giving multiple paths and high reliability.
The internet
The internet is a global WAN of interconnected networks. Key ideas: DNS (translates domain names into IP addresses), hosting, the cloud (remote storage/processing), and web servers and clients.
Protocols and layers
A protocol is a set of rules for communication. Important ones: TCP/IP, HTTP/HTTPS, FTP, SMTP, IMAP. Devices have IP and MAC addresses.
The TCP/IP 4-layer model organises communication: Application, Transport, Internet (Network) and Link (Data Link) layers. Layering keeps each part self-contained and easier to develop and maintain.
Network security
Networks are protected by encryption, firewalls, MAC address filtering and authentication (covered more in Cyber Security).
Exam tips
- Distinguish LAN (small, owned) from WAN (large, e.g. the internet).
- Describe the star topology and its advantages.
- Know the roles of DNS, IP and MAC addresses and key protocols.
- Learn the four TCP/IP layers and why layering is used.