Award up to two marks for a linked explanation such as:
- Devices (can) understand/interpret the data they receive (1) because they follow the same set of rules for communication (1)
- Data is sent in an agreed format/structure (1) so the receiving device can interpret/understand it correctly (1)
- Devices (can) connect/communicate successfully (1) because they agree how the data is transmitted, such as the type of signal used (1)
- Errors (can) be detected/handled (1) because both devices follow the same rules for checking the data (1)
For both marks, the expansion must follow/associate with the statement.
Do not accept 'so devices can talk/communicate with each other' or 'so they can understand each other' without saying they follow the same rules/agreed format.
Do not accept an answer that only states protocols are a set of rules, without saying what this allows (e.g. the data can be understood/interpreted).
Do not accept a faster connection/speed as a reason why protocols are needed.
Do not accept naming a protocol (e.g. TCP/IP, HTTP, Wi-Fi) without an explanation of why it is needed.
Do not accept a description of what a protocol does (e.g. 'TCP splits data into packets') without saying why this is needed.