How is data transmitted across networks, and what do protocols and the TCP/IP stack do?
Data transmission: serial and parallel transmission, packet switching and the structure of a packet, network protocols and the layers of the TCP/IP stack, and the role of standards in communication.
An Eduqas Component 2 answer on data transmission: serial versus parallel transmission with their trade-offs, packet switching and packet structure, the role of network protocols, and the four layers of the TCP/IP stack.
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What this dot point is asking
Eduqas wants you to distinguish serial and parallel transmission, explain packet switching and packet structure, describe the role of network protocols and the layers of the TCP/IP stack, and understand why standards matter. This connects the network hardware of section 3.1 to how data actually moves.
The answer
Serial and parallel transmission
Packet switching and packet structure
Protocols and the TCP/IP stack
Examples in context
Every web page, email and video stream is delivered by packet switching over the TCP/IP stack, which is why a brief network glitch rarely loses your whole download, packets reroute and missing ones are resent. Serial transmission dominates external connections (Ethernet, USB, fibre) precisely for its long-distance reliability. The layered design is why the web (an application-layer protocol) could be invented without redesigning the lower layers. This builds on the network topologies and hardware of section 3.1 and connects to error checking in a later dot point.
Try this
Q1. Which transmission method is more suitable over a long distance, and why? [2 marks]
- Cue. Serial, because parallel transmission suffers from skew (bits arriving out of step) and crosstalk over long distances.
Q2. Name three fields typically found in a data packet. [3 marks]
- Cue. Any three of: source address, destination address, sequence/packet number, payload (data), error-checking data (checksum).
Q3. State the purpose of the internet (IP) layer in the TCP/IP stack. [1 mark]
- Cue. It addresses packets (with source and destination IP addresses) and routes them between networks.
Exam-style practice questions
Practice questions written in the style of WJEC Eduqas exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Eduqas 20205 marksExplain the difference between serial and parallel data transmission, giving one advantage of each, and state which is more suitable for transmission over a long distance.Show worked answer →
Serial (up to 2 marks): bits are sent one after another down a single wire. Advantage: cheaper (fewer wires) and reliable over long distances because there is no skew between wires.
Parallel (up to 2 marks): multiple bits are sent at once down several wires simultaneously. Advantage: can be faster over short distances because several bits travel together.
Long distance (up to 1 mark): serial is more suitable over long distances, because parallel transmission suffers from skew (bits arriving at slightly different times) and crosstalk as distance increases.
Markers reward the one-wire-at-a-time versus several-wires-at-once distinction, a valid advantage of each, and serial for long distances with a reason.
Eduqas 20226 marksDescribe what packet switching is and the typical contents of a data packet, and explain the purpose of dividing the TCP/IP model into layers.Show worked answer →
Packet switching (up to 2 marks): data is divided into small packets that are sent independently across the network, possibly by different routes, and reassembled in the correct order at the destination; this uses the network efficiently and routes around congestion or failures.
Packet contents (up to 2 marks): a packet typically contains the source address, the destination address, a sequence/packet number (for reassembly), the payload (the data itself), and error-checking information such as a checksum.
Layers (up to 2 marks): the TCP/IP model is divided into layers (application, transport, internet, link) so that each layer handles a specific function and can be developed or changed independently; this modularity simplifies design and lets different technologies interoperate.
Markers reward the divide-send-independently-reassemble idea, the packet fields (addresses, sequence number, payload, error check), and the modularity/independence purpose of layering.
Related dot points
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Sources & how we know this
- WJEC Eduqas GCE AS/A Level Computer Science specification (from 2015) — Eduqas (2015)