Data is split into packets before it is sent over the internet.
Explain why each device that receives packets over the internet needs a unique IP address.
Mark scheme
Award up to two marks for a linked explanation such as:
- Data/packets are delivered to the correct/intended device (1) because the destination IP address identifies that device, so a duplicate address would mean packets could be delivered to the wrong device (1)
- Replies are sent back to the device that requested the data (1) because the sender's IP address identifies that device, so a duplicate address would mean the reply could be sent to the wrong device (1)
- The device can be identified separately from other devices (1) so packets are not delivered to a different device that has the same address (1)
For both marks, the expansion must follow/associate with the statement.
Award one mark for a valid point and a second mark only for a linked reason explaining why a duplicate address would cause a problem.
Do not accept 'it is unique'/'it has its own address' as a point, as this repeats the question.
Do not accept 'so it can connect to the internet' or 'so it can be found' on its own without a link to data/packets being delivered to the correct device.
Allow 'data' for 'packets'.
Example answers and how they were marked
Packets are delivered to the correct device because the destination IP address identifies one device, so if two devices had the same address packets could be sent to the wrong one.
Why: Point that packets reach the correct device (1) and linked reason that a duplicate address would cause misdelivery (1).
Packets are sent to the correct device because it has its own IP address.
Why: Valid point that packets reach the correct device (1), but the reason only restates uniqueness and does not explain how a duplicate address would cause a problem, so no second mark.
So that it can connect to the internet.
Why: No link to packets/data being delivered to the correct device; the mark scheme rejects a connection statement on its own.