Lesson 1.3: What is a computer network?
What a computer network is and why security people must understand it: nodes and links, local and wide area networks, the internet as a network of networks, clients and servers, and data travelling in packets. In the lab you look at your own laptop on the office network: its name, its address, its network interfaces, a printer that answers on the same network, and a web server that answers from across the internet.
15 min
You will learn to
- Define a computer network, a node and a link
- Tell a LAN from a WAN and explain what the internet is
- Explain the client-server model
- Explain why data travels in packets
- Find your machine's name, address and interfaces
Key terms
- Computer network
- Two or more devices connected so they can exchange data.
- Node (host)
- Any device on a network that sends or receives data. A host is a node with an address that runs programs, like a computer or a server.
- Link
- The connection between two nodes: a cable, a radio signal (Wi-Fi), a fibre.
- LAN and WAN
- A LAN (local area network) covers one place: a home, an office, a floor. A WAN (wide area network) connects places far apart, like a company's offices in different cities.
- Internet
- The worldwide network of networks: millions of separate networks connected to each other and speaking the same protocols.
- Client and server
- A client asks for something; a server provides it. The same computer can be both.
- Packet
- A small piece of data with the sender's and receiver's addresses on it. Large data is split into many packets.
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