IGCSE Computer Science Paper 1 Definitions Worksheet: 2.1 Data Transmission Types and Methods (Modules 121–130)
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Key terms
Write what each term means, in your own words.
1
different routes
2
packets arrive out of order
3
reordering packets
4
packet switching steps
5
serial transmission
6
parallel transmission
7
skew
8
serial vs parallel
Answer Key
IGCSE Computer Science Paper 1 · Modules 121–130 · Student wording will vary for definitions
1different routes — Packets from one message can take different routes because each router picks the best available path at that moment, avoiding busy or broken links. Routes may take different lengths of time.
2packets arrive out of order — Packets take different routes, so they may reach the destination in a different order from the one sent, e.g. packet 5 before packet 4. Order is not guaranteed.
3reordering packets — After the last packet arrives, the receiving device uses the packet numbers in the headers to put the packets in the right order and joins the payloads to rebuild the message.
4packet switching steps — Data is split into numbered packets, routers pick each packet's route, packets may arrive out of order, then they are reordered to rebuild the data once the last packet arrives.
5serial transmission — Sending data one bit at a time, one after another, down a single wire or channel. The bits arrive in the same order they were sent.
6parallel transmission — Sends several bits at the same time, each down its own wire in the same cable, e.g. 8 bits down 8 wires at once.
7skew — Bits sent together down parallel wires arrive at slightly different times, so data can be received incorrectly. It gets worse as the cable gets longer.
8serial vs parallel — Serial sends 1 bit at a time down one wire: cheaper, reliable, better over long distance. Parallel sends many bits at once down several wires: faster over short distances only.