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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 marksWireless Connections Swap Remove

An office wireless network is near a microwave oven and several other wireless networks.

Explain how interference can affect the speed of a wireless network.

[2 marks]
Mark scheme

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

  • The speed of data transfer is reduced/is slower (1) because interference corrupts the radio signal, so data/packets are lost and have to be resent/retransmitted (1)
  • The network speed is lower (1) because there is more noise on the wireless signal, so data is sent at a lower transmission rate (1)
  • The throughput of the wireless network is reduced (1) because time is used resending corrupted data/packets instead of sending new data (1)

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

Award 1 mark for a statement that the speed/transfer rate is reduced (e.g. slower, takes longer), even if no reason is given.

Do not accept 'interference damages/corrupts the radio signal' or 'the signal is weaker' on its own without a link to the speed.

Do not accept 'data is lost' on its own without saying how this reduces the speed.

Do not accept 'interference increases the bandwidth' or 'interference makes the signal stronger'.

Example answers and how they were marked
Full marks2/2

Interference corrupts the radio signal, so packets are lost and resent, which makes the data transfer slower.

Why: Linked point (1): data transfer is slower; reason (1): interference corrupts the signal so packets are lost and resent.

Some marks1/2

The speed of the wireless network will be lower.

Why: Point only (1): states the effect on speed. No linked reason why interference causes this.

No marks0/2

Interference increases the bandwidth, so the data travels faster.

Why: Misconception that interference increases bandwidth; the mark scheme says not to accept this.

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