Networking Exam Practice

This final lesson brings together everything from the course in a series of exam-style concepts and worked examples. Use this as a revision checklist and a guide to the type of answers that earn full marks at A-Level.

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Key Definitions You Must Know

Term	Definition
Protocol	A set of rules that governs communication between devices on a network
Bandwidth	The maximum rate at which data can be transmitted over a network link, measured in bits per second (bps)
Latency	The delay between sending data and it arriving at its destination
Throughput	The actual rate of successful data transfer (may be lower than bandwidth due to congestion, errors, etc.)
Packet	A unit of data transmitted over a network, containing a header (source/destination addresses, sequence number) and a payload
MAC address	A 48-bit physical address permanently assigned to a network interface (e.g. A1:B2:C3:D4:E5:F6)
IP address	A logical address assigned to a device on a network (IPv4: 32-bit; IPv6: 128-bit)
Router	A device that forwards packets between different networks based on IP addresses
Switch	A device that forwards frames within a local network based on MAC addresses
Gateway	A device that connects two networks that use different protocols

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How Packet Switching Works

Most data on the Internet is transmitted using packet switching:

1. The data is divided into packets, each labelled with source address, destination address, and a sequence number.
2. Each packet is routed independently — different packets may take different routes.
3. Routers examine the destination address in each packet and forward it toward the destination using routing tables.
4. At the destination, packets are reassembled in the correct order using the sequence numbers.
5. If a packet is lost or corrupted, TCP requests retransmission.

Advantages of Packet Switching

Advantage	Explanation
Efficient	Network capacity is shared — no dedicated path is reserved
Robust	If a route fails, packets can be rerouted via alternative paths
Scalable	Works well for millions of simultaneous connections

vs Circuit Switching

In circuit switching (used by traditional telephone networks), a dedicated communication path is established for the duration of the call. The path is reserved even when no data is flowing, which wastes bandwidth. Packet switching is more efficient for bursty data traffic (web browsing, email).

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Exam Technique: Comparing Protocols

When comparing protocols (e.g. TCP vs UDP, HTTP vs HTTPS, IPv4 vs IPv6), use a structured approach:

1. State what each protocol does — one sentence each.
2. Identify key differences — use a table if possible.
3. Give appropriate use-cases for each.
4. Explain why one is preferred over the other in a given scenario.

Example: Compare TCP and UDP (6 marks)

TCP (Transmission Control Protocol) is a connection-oriented protocol that provides reliable, ordered delivery of data using acknowledgements and retransmission. UDP (User Datagram Protocol) is a connectionless protocol that provides fast, unreliable delivery with minimal overhead.

Feature	TCP	UDP
Connection	Established (3-way handshake)	None
Reliability	Guaranteed (ACKs + retransmission)	No guarantee
Ordering	Segments delivered in order	No ordering
Speed	Slower (overhead)	Faster
Use-case	Web browsing, email, file transfer	Video streaming, VoIP, online gaming