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Edexcel GCSE Computer Science (1CP2) Exam Questions

Build a practice paper from 693 exam-style questions, each with its mark scheme and example answers. Print it, or answer it on paper and then open the mark schemes. Or browse the questions by topic.

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3 questions · 5 marks

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1Multiple choice1 markAddressing Swap Remove

A packet of data is sent across the internet to a web server. The packet has a header that stores information about the packet.

Identify the information in the packet header that a router uses to forward the packet towards its destination.

[1 mark]
  • AThe destination domain name
  • BThe destination IP address
  • CThe MAC address of the sender
  • DThe name of the file being sent
Mark scheme
  • B The destination IP address (1)
  • The only correct answer is B. The correct answer is the destination IP address.
  • A is not correct because a domain name is converted to an IP address by a DNS server before routing begins
  • C is not correct because the sender's MAC address is only used to deliver the packet on the local network
  • D is not correct because the file name is not used to route packets
Example answers and how they were marked
Full marks1/1

B The destination IP address

Why: Correct option (1): a router reads the destination IP address in the header to forward the packet towards its destination.

No marks0/1

A The destination domain name

Why: A domain name is converted to an IP address by a DNS server before routing begins, so it is not the routing information in the header (mark scheme line A); no mark.

No marks0/1

C The MAC address of the sender

Why: The sender's MAC address is only used to deliver the packet on the local network, so it is not used by the router to forward the packet (mark scheme line C); no mark.

2Explain2 marksPacket Switching Swap Remove

Data is split into packets before it is sent across the internet.

Explain why each packet has a packet number in its header.

[2 marks]
Mark scheme

Award up to two marks for a linked explanation such as:

  • The receiver can put the packets back into the correct order (1) because packets may arrive out of order/take different routes (1)
  • The receiver can see if a packet is missing (1) because the sequence of numbers shows a gap (1)
  • The receiver knows when the whole file has arrived (1) because the total number of packets/last packet number is known (1)

For both marks, the expansion must follow/associate with the statement.

Allow 'so the packets can be put back in the correct order/reassembled' for the first mark, but the second mark needs the reason, i.e. packets may arrive out of order/take different routes.

Do not accept 'so the packets can be identified' without stating what the number is used for, e.g. reordering or spotting a missing packet.

Do not accept 'so the router knows where to send it' - the router uses the destination IP address, not the packet number.

Example answers and how they were marked
Full marks2/2

The receiver can put the packets back in the correct order because they may arrive out of order.

Why: Linked point (1) and reason (1): the packet number allows reordering because packets can arrive out of order.

Some marks1/2

It shows the receiver the order of the packets.

Why: The point is given (1) but there is no linked reason, such as packets arriving out of order.

No marks0/2

So the router knows which route to use.

Why: Routers use the destination IP address, not the packet number, so this earns nothing; it is named in the mark scheme as a 'Do not accept'.

3Explain2 marksTopologies Swap Remove

A bus topology has a terminator at each end of its cable.

Explain why terminators are needed in a bus topology.

[2 marks]
Mark scheme

Award up to two marks for a linked explanation such as:

  • Terminators absorb the signal at the ends of the cable (1) so it is not reflected back along the bus (1)
  • Terminators prevent signals reflecting/bouncing back (1) so the reflected signal does not corrupt data on the cable (1)
  • Terminators absorb the signal (1) so it does not collide/interfere with data being sent by other devices (1)
  • Terminators stop the signal reflecting back down the cable (1) so data can be transmitted and received without errors (1)

For both marks, the expansion must follow/associate with the statement.

Allow 'interfere'/'corrupt' only where the answer says the reflected signal mixes with/collides with data on the cable.

Do not accept 'to stop the signal' on its own, as stopping the signal is not the same as stopping it reflecting back along the cable.

Do not accept 'to terminate the cable/network', 'to end the cable' or 'to stop the cable breaking'.

Do not award responses that only repeat the stem, e.g. 'because there is a terminator at each end'.

Example answers and how they were marked
Full marks2/2

Terminators absorb the signal at each end of the cable so that it does not reflect back along the bus.

Why: Linked point (1) and reason (1): absorbing the signal is linked to it not being reflected back along the bus.

Some marks1/2

Terminators absorb the signal at the ends of the cable.

Why: Awarded 1 mark for the point that the signal is absorbed, but no linked consequence is given.

No marks0/2

They terminate the network so the cable does not break.

Why: No credit: it does not say the signal is absorbed or that reflections are prevented, and the mark scheme rejects 'to terminate the network' and 'to stop the cable breaking'.

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