In simple terms
A friendly intro before the formal notes — no formulas yet.
The Digital Postal Service
Computers are like individual houses, and networks are the roads that connect them. The internet is the worldwide system of all roads, allowing messages (data) to be sent from any house to any other.
Imagine you want to send a multi-page letter to a friend across the country. Instead of one big envelope, you tear each page out, put it in a separate, smaller envelope, and write your friend's address and a page number (e.g., 'page 1 of 5') on each one. The postal service (the network) sends each envelope on the fastest route available, which might be different for each one. When they arrive, your friend uses the page numbers to reassemble the letter in the correct order. This is exactly how packet switching works on the internet.
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A computer, or 'client', requests information, like a webpage. This request is broken down into small pieces of data called packets.
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Each packet is labelled with the destination address (the server's IP address) and its own sequence number, like a numbered parcel.
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Network devices like routers act as digital sorting offices, reading the address on each packet and forwarding it along the most efficient path towards the destination server.
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The destination server receives the packets, which may arrive out of order. It uses the sequence numbers to reassemble them correctly and send the requested webpage back to the client, again as packets.
Explore the concept
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Full topic notes
Formal explanation with the rigour you need for the exam.
Building Blocks: Computers and Local Networks
At its core, a computer is a device that processes data. When we connect multiple computers and peripherals (like printers) in a confined area, such as an office or a school, we create a Local Area Network (LAN). This allows for shared resources and communication. Devices on a LAN are typically connected via Ethernet cables or wirelessly (Wi-Fi) to a central device called a switch, which intelligently forwards data only to the intended recipient device within the network.
Computer: A programmable electronic device for storing and processing data.
LAN (Local Area Network): Confined to a small geographical area (e.g., one building). High speed, low cost, and privately owned.
Switch: A device that connects multiple devices on a LAN and directs traffic between them efficiently.
Wi-Fi: A wireless technology standard used for creating LANs.
The Internet: A Global Network of Networks
The internet is not a single entity but a vast, global collection of interconnected public and private networks, from large corporate LANs to your small home network. It is a Wide Area Network (WAN). Your gateway to this global network is your Internet Service Provider (ISP). A device called a router is crucial here; it connects your entire LAN to the ISP's network, directing traffic between your local devices and the wider internet.
In exam questions, be precise with your terminology. Do not use 'internet' and 'World Wide Web' (WWW) interchangeably. The internet is the global network infrastructure (the hardware and protocols), while the WWW is one of the services that runs on the internet (the system of interlinked web pages and resources).
The Rules of the Road: Protocols and Data Transmission
For data to travel reliably across this complex system, it needs a set of rules, or protocols. The most important is the TCP/IP suite. When you request a webpage, TCP breaks your request into small packets. IP then addresses each packet with the destination server's IP address. These packets are sent independently via packet switching, with routers directing them across the internet. At the destination, TCP reassembles the packets in the correct order. To find the IP address in the first place, your computer uses the Domain Name System (DNS), which acts like the internet's address book, translating a website name like 'ibo.org' into a numerical IP address.
TCP/IP: The core protocol suite. TCP handles packet creation/reassembly and error checking. IP handles addressing and routing.
Packet Switching: Data is broken into packets, sent independently, and reassembled at the destination. This is efficient and robust.
Router: Connects different networks together (e.g., your LAN to the internet) and directs packets towards their final destination.
DNS (Domain Name System): Translates human-friendly domain names into computer-friendly IP addresses.
Worked examples
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A new secondary school is setting up its first IT suite with 30 desktop computers, a shared printer, and a central file storage system. Explain why a client-server LAN would be a suitable network architecture for this scenario, identifying two key hardware components required.
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Switch: A network switch is required to connect all 30 computers, the server, and the printer. It will manage the flow of data within the LAN, ensuring that a print job from one computer goes directly to the printer without congesting the rest of the network. [1 mark]
A user types 'www.example.com' into their web browser and presses Enter. The page loads successfully. Outline the key steps involving DNS and TCP/IP that occur to make this happen.
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DNS Lookup: The user's computer does not know the IP address for 'www.example.com'. It sends a request to a DNS server. [1 mark] The DNS server looks up 'www.example.com' in its database and returns the corresponding IP address (e.g., 93.184.216.34) to the user's computer. [1 mark]
How it all connects
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Glossary
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Quick check
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Revision flashcards
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What is a Local Area Network (LAN)?
A network that connects computers and devices in a limited geographical area such as a home, school, or office building. Typically owned and managed by a single organisation.
Key takeaways
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Computer: A programmable electronic device for storing and processing data.
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LAN (Local Area Network): Confined to a small geographical area (e.g., one building). High speed, low cost, and privately owned.
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Switch: A device that connects multiple devices on a LAN and directs traffic between them efficiently.
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Wi-Fi: A wireless technology standard used for creating LANs.
Practice — then mark it
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