Describe how packet switching is used to transmit messages across a network.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2024). The mark or mark type is shown in brackets.

1. [3] MP1 The data to be transmitted is divided into equal sized packets
2. [3] MP2 A packet header is attached to each packet containing key information ... such as source/destination IP addresses, packet number, etc
3. [3] MP3 Packets are transmitted independently
4. [3] MP4 and may travel though different routes/paths to the destination
5. [3] MP5 Routes are determined using a routing table//Packets take the optimum route depending on congestion
6. [3] MP6 The packets usually arrive out of order
7. [3] MP7 The packets are reassembled in the correct order at the destination // The packets are re-ordered using the sequence number/the header
8. [3] MP8 If packets are missing/corrupted a re-transmission request is sent / packets are re-sent.
9. [4] MP1 Packets are more likely to arrive because they can be re-routed if a problem occurs with one of the routes//Packets are more likely to arrive because if a packet is lost, it can be re-transmitted
10. [4] MP2 Bandwidth can be shared allowing packets from different messages to share the same path
11. [4] MP3 Considered secure as the packets generally travel via different routes
12. [4] MP4 High data transmission rate is possible
13. [4] MP5 Time delay because packets need to be re-ordered/reassembled at the destination//Time delay caused by missing packets needing to be re-sent//Time delay because it has to share the bandwidth of the circuit / channel with other packets
14. [4] MP6 Requires a complex algorithm to function
15. [4] MP7 Needs lots of RAM to handle large amounts of data.