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Network Protocols and Packet Switching: Question 6

Syllabus 14.1

Multiple choice A2 1 mark

A group of A Level Computer Science students is making revision flashcards, one for each layer of the TCP/IP protocol suite. On the flashcard for the Internet layer, they want to write a single sentence that correctly describes what that layer is responsible for.

Which sentence correctly describes the purpose of the Internet layer?

Choose an answer to check it, then compare with the worked solution below.
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Worked solution

Why B is correct

The Internet layer of the TCP/IP suite is responsible for logical (IP) addressing, attaching the source and destination host’s IP address to each packet, and for getting each packet across from its own network to the destination’s network, however many networks lie in between. This is the layer at which routers operate: a router reads a packet’s destination IP address and selects the next network the packet should be forwarded towards. This matches option B exactly.

Why the other options are wrong

  • A describes the Transport layer: breaking data into segments and providing reliable end-to-end delivery between the correct application on each host, using port numbers, is the Transport layer’s job, not the Internet layer’s.
  • C describes the Application layer: providing the user-facing software and protocols (such as HTTP and SMTP) that people and their programs interact with directly.
  • D describes the Link layer: handling the physical transmission of data, and the hardware (MAC) addressing, across a single local link to the next device on that same link, not the logical, network-to-network addressing used by the Internet layer.

Final answer

  • B. The Internet layer adds logical (IP) addressing to each packet and is the layer at which routers select each packet’s path across different networks.