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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 markPacket Switching Swap Remove

A computer sends an email to a server on another network.

Identify the information in a packet header that a router uses to decide where to send the packet.

[1 mark]
  • ADestination IP address
  • BMAC address
  • CPacket number
  • DSource IP address
Mark scheme
  • A Destination IP address (1)
  • The only correct answer is A. A router reads the destination IP address in a packet header to forward the packet towards its destination.
  • B is not correct because a MAC address identifies a device on a local network and is not used to route packets across the internet
  • C is not correct because the packet number is used at the destination to put the packets back into the correct order
  • D is not correct because the source IP address shows where the packet came from, not where it is going
Example answers and how they were marked
Full marks1/1

A Destination IP address

Why: Selected the destination IP address, the header information a router reads to forward the packet (1).

No marks0/1

D Source IP address

Why: A near miss: the source address is in the header, but it shows where the packet came from, so it is not used to decide where the packet is sent.

No marks0/1

B MAC address

Why: Typical misconception reported by examiners: a MAC address identifies a device on a local network and is not used to route packets across the internet.

2Short recall2 marksWireless Connections Swap Remove

Latency affects the performance of a network.

Define the term latency.

[2 marks]
Mark scheme

Award one mark for any of the following up to a maximum of two marks:

  • A delay/time/lag (1)
  • Between a signal/request being sent and a response/data being received (1)

Allow 'the time taken for data to travel from source to destination' for both marks.

Do not accept 'the speed at which data travels' / 'bandwidth' / 'the amount of data sent per second'.

Example answers and how they were marked
Full marks2/2

The delay between a signal being sent and a response being received.

Why: Gives the delay (1) and the time between sending and receiving (1).

Some marks1/2

The time taken for data to travel.

Why: Gives the idea of time taken (1) but does not say between sending and receiving (1).

No marks0/2

The speed at which data is sent over the network.

Why: Describes speed, not latency; no creditworthy point.

3Explain2 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'.

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