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Edexcel GCSE Computer Science (1CP2) Exam Questions

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4 questions · 8 marks

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1Describe2 marksWired Connections Swap Remove

A hospital connects the computers on a ward using wired connections.

Describe how using wired connections can reduce latency on this network.

[2 marks]
Mark scheme

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

  • Data travels along the cable directly to the switch on a single continuous path (1) so the time between sending and receiving the data is short (1)
  • A cable is not affected by interference from other devices/wireless traffic nearby (1) so packets are not lost and resent, which would add to the delay (1)
  • The switch sends the data only to the port of the correct device, not to every device (1) so the data spends less time travelling and the delay is lower (1)
  • Fewer devices share a cable than share a wireless channel (1) so packets do not queue/wait before they are sent (1)

The first mark is for the way the wired connection carries the data; the second mark is for how this reduces the delay between sending and receiving.

Do not accept responses about bandwidth or the amount of data a cable can carry, as latency is the delay between sending and receiving.

Do not accept responses that confuse latency with speed/bandwidth, e.g. 'a wired connection is faster so there is less latency', unless they describe how the delay is reduced.

Do not accept answers that only say a wired connection is faster, with no link to the delay.

Example answers and how they were marked
Full marks2/2

The cable is not affected by interference from other devices so packets do not need to be resent and the delay stays low.

Why: First mark for the cable being free of interference (1); linked development that no packets are resent and so the delay is lower (1).

Some marks1/2

There is no interference from other devices on a cable.

Why: Gives the first point of a linked pair (1) but does not say how this reduces the delay between sending and receiving.

No marks0/2

Wired connections have a higher bandwidth so there is less latency.

Why: Confuses bandwidth with latency, which the 'Do not accept' lines rule out (0).

2Explain2 marksPacket Switching Swap Remove

A file is sent across the internet in packets.

Explain why packets from the same file may take different routes.

[2 marks]
Mark scheme

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

  • Each router chooses the best route at the time (1) so when a route becomes busy/congested or fails, later packets are forwarded along a different path (1)
  • Routers forward each packet separately (1) so the path a packet takes depends on the traffic conditions when that packet arrives (1)
  • A router may send a packet to a different next router (1) if its routing table shows a better/less congested route for that packet (1)
  • Traffic on the internet changes (1) so no single path is kept for the file and each packet can use whichever route is best when it is sent (1)

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

Allow reference to a routing table, or to how a router decides the route, as part of the linked reason.

Do not accept 'the packets have different IP addresses' because all packets from the same file have the same destination IP address, even though their routes can differ.

Do not accept 'the internet is busy' or 'there is a lot of traffic' on its own without linking this to the router choosing a different route.

Do not accept 'different routers send the packets' on its own without a reason why a different router/route is chosen.

Do not accept an answer that only says the packets take different routes without explaining why.

Example answers and how they were marked
Full marks2/2

Each router chooses the best route at the time, so if one route becomes busy or fails, later packets are sent a different way.

Why: Linked point (1) that each router chooses the best route at the time and reason (1) that a busy or failed route means later packets take a different path.

Some marks1/2

Routers send packets along the least congested route.

Why: States that a router chooses the least congested route (1) but gives no linked reason why this makes the packets from the file take different routes.

No marks0/2

Because each packet is given a different IP address so they go to different places.

Why: Misconception named in the mark scheme: all packets from the same file share the same destination IP address, even though their routes can differ.

3Explain2 marksThe Internet Swap Remove

Each data packet has a header that contains the destination IP address.

Explain one reason why a data packet contains the destination IP address.

[2 marks]
Mark scheme

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

  • Routers can forward the packet towards its destination (1) because they read the destination IP address in the packet header (1)
  • The packet is delivered to the correct device (1) because the receiving device compares the destination IP address with its own IP address (1)
  • Each packet can take a different route (1) because routers use the destination IP address to choose the next router (1)
  • The packet can be passed on by each router in turn (1) because the destination IP address shows which network the packet is for (1)

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

Statements such as 'so it reaches the right destination' or 'so routers know where to send it' earn the first mark only; do not award the second mark unless the reason says that the address is read from the packet header and used to forward the packet.

Do not accept 'so it knows where it came from' as this describes the source address, not the destination address.

Do not accept 'so it gets there faster' without a linked reason.

Example answers and how they were marked
Full marks2/2

Routers know where to send it because they use the address in the packet header to choose the next network.

Why: Linked point (1) and reason (1): routers read the destination IP address in the header to forward the packet.

Some marks1/2

So that it reaches the right destination because every packet has an address.

Why: First mark (1) for reaching the right destination, but the reason is circular and does not say the address is read and used to forward the packet.

No marks0/2

So the packet knows where it came from.

Why: Describes the source address, not the destination address; do not accept.

4Explain2 marksWired Connections Swap Remove

Latency is the delay between data being sent and received. A player of online games uses a wired Ethernet connection instead of a wireless connection.

Explain one reason why the wired connection can have a lower latency.

[2 marks]
Mark scheme

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

  • The cable provides a direct physical path to the switch/router (1) so data does not have to travel through the air where it can be delayed by obstacles such as walls (1)
  • The cable is not shared with other wireless devices (1) so data does not have to wait for a free channel before it is sent (1)
  • The data travels straight along the cable to the switch (1) so the time taken for it to reach its destination is short (1)

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

Do not accept 'the wired connection is faster' on its own without saying why the delay between sending and receiving is shorter.

Do not accept a definition of latency without a reason.

Example answers and how they were marked
Full marks2/2

The cable gives the computer a direct physical path to the switch, so the data does not have to travel through the air where it could be delayed by obstacles.

Why: Gives the point of a direct physical path (1) and links it to data not being delayed by obstacles in the air (1).

Some marks1/2

The wired connection gives a direct path, so it is quicker.

Why: Gives the point about the direct path (1) but 'quicker' only restates lower latency and does not explain why the delay is shorter.

No marks0/2

Wired connections have lower latency because the internet speed is faster.

Why: Confuses speed with latency; no reason is given for a shorter delay, and 'faster' on its own is not accepted.

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5.3 Cybersecurity

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