The Internet layer and Link layer are two layers of the TCP/IP protocol suite.

Mark scheme

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

1. [5] One mark per mark point (Max 5)
2. One mark per mark point for purpose of Internet Layer (Max 3)
3. MP1 To identify the intended network and host.
4. MP2 To add header containing IP addresses. // To address packets with their source and destination IP Addresses.
5. MP3 To prepare packets for delivery by formatting them into datagrams.
6. MP4 To route datagrams through the optimum route over a network.
7. One mark per mark point for purpose of Link Layer (Max 3)
8. MP5 To prepare the next hop by managing the link between two directly connected devices. // To identify and move traffic across local segments.
9. MP6 To format datagrams into frames for transmission.
10. MP7 To identify network protocols in the packet header. // To ensure correct network protocols are/is followed.
11. MP8 To deliver frames to the receiving network. // To receive frames from the sending network. // To map IP addresses to MAC physical addresses.
12. MP9 To provide error checking/error correction/recovery/reconstruction
13. MP10 including resend requests.
14. [4] One mark for each correct marking point (Max 4)
15. MP1 The router reads the IP address of the destination from the packet header.
16. MP2 A router uses a routing table to find information
17. MP3 about e.g., available hops / netmask / gateway used / adjacent routers / the status of the routers along the route.
18. MP4 The router determines the next hop / optimum route. // The router sends the packet on its next hop.
19. MP5 The router manages the hop counter // The hop counter is reduced by 1 every time the packet passes a router.