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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 · 6 marks

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1Explain2 marksPacket Switching Swap Remove

A router connects a home network to the internet.

Explain how a router uses the destination IP address in a packet header.

[2 marks]
Mark scheme

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

  • The router reads the destination IP address (1) so it knows which network/device the packet is for (1)
  • The router looks up the destination IP address in its routing table (1) to find the next router/route for the packet (1)
  • The router forwards the packet to the next router (1) that leads towards that IP address / is on the best route (1)

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

Do not accept MAC address - routers use the IP address to route packets between networks.

Do not accept 'it finds the exact device' without saying how the router uses the address, e.g. routing table/next router.

Example answers and how they were marked
Full marks2/2

The router looks up the destination IP address in its routing table to find the next router to send the packet to.

Why: Linked point (1) and reason (1): looks up the destination IP address in the routing table to find the next router.

Some marks1/2

It reads the destination IP address.

Why: Reads the destination IP address (1) but gives no linked reason about a routing table or next router.

No marks0/2

It reads the MAC address so it knows which computer sent the packet.

Why: Routers use the IP address to route packets, not the MAC address; no creditworthy point.

2Explain2 marksProtocols & Layers Swap Remove

The TCP/IP model has four layers.

Explain one function of the transport layer when a file is sent over a network.

[2 marks]
Mark scheme

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

  • Splits the data/file into packets (1) so each packet can be sent separately across the network (1)
  • Adds a packet/sequence number to each packet (1) so the packets can be put back into the correct order at the destination (1)
  • Detects lost/missing packets (1) so they can be requested/resent (1)
  • Creates a connection between the two computers/hosts (1) before the file is sent (1)

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

Allow 'segments' for 'packets' (TCP divides the data into segments, which become packets at the internet layer).

Do not accept 'sends the data/file' on its own without saying what the transport layer does to the data.

Do not accept naming TCP or a port number on its own without expansion.

Do not accept routing/addressing packets using IP addresses, which is the internet layer.

Example answers and how they were marked
Full marks2/2

The transport layer splits the data into packets so each packet can be sent separately across the network.

Why: Linked point (1) and reason (1): splitting into packets lets each one be sent separately.

Some marks1/2

It splits the data into packets.

Why: Point (1) identified, but no linked reason given, so only the first mark is awarded.

No marks0/2

It routes the packets using IP addresses so they reach the right destination.

Why: Routing using IP addresses is the internet layer, not the transport layer, so no credit is given.

3Explain2 marksAddressing Swap Remove

A laptop is used at home and is then taken on holiday, where it connects to a different network.

Explain why the laptop is given a different IP address when it is used on holiday.

[2 marks]
Mark scheme

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

  • The laptop is connecting to a different network (1) so it needs an address that belongs to/is unique on that network (1)
  • The router/ISP on the new network assigns the address (1) because addresses are given out by the network the device is connected to (1)
  • The home IP address is only valid on the home network (1) so it cannot be used to send data on another network (1)

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

Do not accept 'it has a dynamic IP address' on its own, as this repeats the question.

Do not accept answers that say the IP address is stored in the device's hardware/network card, as this describes the MAC address.

Example answers and how they were marked
Full marks2/2

It is connecting to a different network now, so the router there gives it an address that works on that network.

Why: Point that the laptop is on a different network (1) and linked reason that the new router assigns an address valid/unique on that network (1).

Some marks1/2

Because it is connecting to a different network.

Why: A valid point (1) but no linked reason about where the new address comes from or why the old one cannot be used.

No marks0/2

Because the IP address is built into the laptop's network card and it changes when it is plugged into a new network.

Why: Misconception: an address fixed in the hardware is the MAC address; the mark scheme says not to accept this, so no marks.

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