(a) Which of the following best describes the concept of "layers" in network protocols? Tick (✓) one box.

Statement	Tick (✓)
A physical cable that connects different switches together.
A division of network functionality into self-contained sections.
A security measure that stops hackers entering a network.
The speed at which data travels across the network.

(b) The TCP/IP model is the standard model used for the Internet.
Complete the diagram below by writing the names of the missing layers in the correct order.

Layer Number	Layer Name
Layer 4	Application Layer
Layer 3
Layer 2	Internet Layer
Layer 1

Different protocols operate at different layers of the TCP/IP stack.
Draw a line to match each protocol to the layer it operates in.

Scenario:
A software engineer is designing a new email program. They only need to write code for the Application Layer and do not need to worry about how the data is physically transmitted through cables (the Link Layer).

Explain two benefits of using layers that allow the engineer to work in this way.

When data is sent from one computer to another, it moves down the layers at the sender's end and up the layers at the receiver's end.

(a) Describe what happens to the data as it moves down the layers (from Application to Link) before it is sent.
(b) Describe what happens to the data as it moves up the layers (from Link to Application) when it arrives at the receiver.

Extended Short Answer:
A company manufactures network interface cards (NICs). These cards operate at the Link Layer.

Explain why the manufacturer of the NIC does not need to know which web browser (e.g., Chrome, Edge) the user will be running at the Application Layer.