A restaurant has an electronic ordering system. The system allows customers to select the food they want to order. The data for the order is transmitted across their network to a computer in the restaurant kitchen.

Mark scheme

Marking points from the official mark scheme (May/June 2025). The mark or mark type is shown in brackets.

1. [2] Two from (one mark for serial, one mark for full-duplex): serial • Serial is suitable as data may be travelling a long distance (over 5 metres). • Serial is suitable to make sure that bits don't arrive skewed/arrives in order. • Serial is suitable as there is less chance of error. • Serial has sufficient transmission speed as not much data being sent. full-duplex • Full-duplex is suitable as data needs to go between customer and kitchen computer // data needs to go in both directions // so notification of errors can be sent back to customer.
2. [1] The data may be transmitted faster.
3. [5] Any five from: • The checksum is calculated from/using the data. • using an algorithm // by example. • The (checksum) value is transmitted with the data. • The (checksum) value is recalculated after transmission/by recipient. • If the checksum values do not match, an error is detected // If the checksum values match, no error is detected ... • ... request for data to be resent if there is an error.
4. [1] Any one from: • Parity byte/block check • Echo check
5. [1] D
6. [2] Any Two from: • The packets arrive in the wrong order. • Each packet could take a different route. • Some packets may take longer than others to be transmitted. • Some packets may not arrive/be corrupted and need to be requested again.