Edexcel GCSE Computer Science (1CP2) Exam Questions

• C 32 (1)
• The only correct answer is C. The correct answer is 32.
• A is not correct because 4 is the number of groups of numbers in an IPv4 address
• B is not correct because 8 is the number of bits in each group of an IPv4 address
• D is not correct because 128 is the number of bits in an IPv6 address

• C To reassemble the packets in the correct order (1)
• The only correct answer is C. The correct answer is To reassemble the packets in the correct order.
• A is not correct because error checking uses the error checking data in the packet, not the packet number
• B is not correct because the destination IP address identifies the destination device, not the packet number
• D is not correct because routers use the destination IP address to choose the route, not the packet number; routers may briefly buffer packets but do not use the packet number to store them

• B 32 (1)
• The only correct answer is B. The correct answer is 32.
• A is not correct because 8 is the number of bits in one part of an IPv4 address, not the whole address
• C is not correct because 128 bits is the length of an IPv6 address
• D is not correct because 256 is the number of possible values in one 8-bit part of an IPv4 address

Award one mark for:

• A (time) delay between data/a signal being sent and being received (1)

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

Allow 'the time taken for data to arrive at its destination after it is sent'

Allow 'time lag/time delay'

Do not accept the amount of data that can be transferred per second (this is bandwidth)

Do not accept the speed of the connection/how fast data travels (this is speed, not latency)

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

• Each IP address is unique (1) so data is sent to the correct device and not to any other device (1)
• The IP address identifies the device on the network (1) so that routers can forward packets towards it (1)
• The IP address shows which network a device is on (1) so routers can direct packets towards that network (1)
• A device needs an IP address (1) to send and receive data across the internet (1)

Do not accept MAC addresses or 'physical address'.

Do not award credit for responses about how an IP address is assigned.

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

• Protocols are rules/standards for communication (1) so that devices can exchange data (1)
• Devices must use the same protocol (1) so that they can understand the format/order of the data (1)
• Protocols set how data is sent and received (1) so that the receiving device can interpret it correctly (1)

Do not accept a bare definition such as 'a protocol is a set of rules' without a link to communication/exchanging data.

Do not accept answers that only name a protocol (e.g. TCP/IP, HTTP) without describing why protocols are needed.

Do not accept responses that describe hardware such as routers or cables as protocols.

For both marks, the development must explain why the rules/standard are needed.

Do not award two marks for two statements that make the same point.

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

• IPv4 addresses are 32-bit (1) so there are only about 4 billion of them/not enough for every device (1)
• More devices are connecting to the internet than IPv4 can address (1) so a larger range of addresses is needed (1)
• IPv6 uses 128-bit addresses (1) so far more devices can be given an address (1)

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

Do not accept 'IPv6 is newer/better/faster/more secure' without a link to the number of addresses available.

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.

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

• The twisted pair/shielded cable resists interference from the cutting machines (1) so the signal is not disrupted/corrupted and data does not need to be resent, so the network speed/throughput stays high (1)
• The cable is less affected by the interference (1) so fewer data packets are corrupted/need resending, so effective throughput/speed is not reduced (1)
• A wired connection gives a consistent/stable speed (1) because the signal is not disrupted by the machines, so data is not resent and speed is not reduced (1)

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

Allow 'consistent/stable speed' as a point, but the linked reason must say that interference no longer disrupts the signal so data is not resent/throughput is not reduced.

Do not accept 'wired connections are faster' on its own without saying why the interference no longer affects the signal/speed.

Do not accept 'there is less interference' on its own without saying what this does to the signal/data (e.g. it is not disrupted/corrupted, so data is not resent).

Do not accept 'reliable' on its own without linking it to speed/throughput.

Do not accept answers about the length of the cable or the number of devices on the network.

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

• Wireless signals can be blocked or absorbed by walls (1) so the data must be re-sent, which adds delay (1)
• A device further from the access point has a weaker signal (1) so data must be re-sent/transmitted at a lower rate, adding delay (1)
• Devices on a wireless network share a channel (1) so a device must wait its turn to transmit, which adds delay (1)
• Interference from other devices affects the radio signal (1) so data must be re-sent, adding delay (1)

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

Allow 'waiting to send' or 'collisions' as the delay caused by devices sharing a channel.

Do not accept 'wireless is slower than wired' on its own, as this repeats the question.

Do not accept a reason that only affects download speed/bandwidth (e.g. 'files take longer to download') without a link to delay.