Networks & the Internet is a core part of A-Level Computer Science. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
LAN & WANLocal and wide area networks.
ProtocolsRules for communication, e.g. TCP/IP, HTTP.
TopologiesNetwork layouts such as star and mesh.
The internetA global network of interconnected networks.
PacketsData split into packets for transmission.
DNSTranslates domain names into IP addresses.
TCP/IP stackFour-layer model: Link, Internet, Transport, Application - underpinning the modern internet.
TCPConnection-oriented transport with handshake, sequence numbers, retransmission and flow control.
UDPConnectionless transport: low overhead, no retransmission; suits streaming and DNS lookups.
IPv432-bit address scheme yielding about 4.3 billion addresses (e.g., 192.168.0.1).
IPv6128-bit address scheme yielding 3.4x10^38 addresses (e.g., 2001:db8::1).
Three-way handshakeTCP connection setup: SYN, SYN-ACK, ACK between client and server.
BinaryBase-2 representation using only 0s and 1s.
HexadecimalBase-16, a shorthand for binary (0–9, A–F).
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
Are the internet and the World Wide Web the same?✗ Yes, they are the same thing. ✓ No — the internet is the global network; the web is one service on it.
What does a router do?✗ Stores all the websites you visit. ✓ Connects different networks and directs data between them.
How many layers are in the OSI model?✗ 4 (confusing with TCP/IP model). ✓ 7 (Physical, Data Link, Network, Transport, Session, Presentation, Application).
Why is UDP used for live video streaming despite being unreliable?✗ Because TCP cannot handle video data. ✓ Lower overhead and latency - retransmitting late packets would harm real-time quality.
Which item is removed first from a stack?✗ The first one added (FIFO). ✓ The most recently added (top) - LIFO.
Practise Networks & the Internet — free games
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