Which layer of the OSI model utilizes IP?

The Network layer is responsible for the logical addressing and routing of data packets across different networks, and it is at this layer that the Internet Protocol (IP) operates. IP plays a crucial role in determining the best path for data transmission between devices on separate networks. It encapsulates data received from the Transport layer into packets that can be sent over the network, providing essential services such as addressing and packet forwarding.

In the context of the OSI model, the Network layer focuses on packet routing through various interconnected networks. It ensures that data can be successfully sent from a source device to a destination device, even if they belong to different networks. This overarching responsibility of routing and addressing is what distinctly identifies the Network layer's use of IP.

The other layers mentioned are responsible for different functions. The Transport layer handles end-to-end communication and data flow control, the Data Link layer deals with node-to-node data transfer within the same network, and the Application layer provides interfaces for user applications. None of these layers utilize IP to facilitate their respective functions, which further solidifies why the Network layer is the correct choice when asked about the layer that utilizes IP.