Which of the following is not a layer of the TCP/IP protocol stack?

The TCP/IP protocol stack is composed of four primary layers: the Application Layer, the Transport Layer, the Internet Layer (which corresponds to the Network Layer in this context), and the Link Layer. The Physical Layer is commonly associated with other protocol models, such as the OSI model, where it represents the physical connection between devices and the transmission of raw data over a physical medium.

In the context of the TCP/IP protocol stack, the Physical Layer does not exist as a separate layer. Instead, it falls under the responsibilities of the Link Layer, which handles both data link and physical aspects of network communication. Therefore, the correct identification of the Physical Layer as not being part of the TCP/IP framework highlights the fundamental differences between protocol stacks and their respective layers, reinforcing a critical understanding of network architecture.