Certified Information Systems Security Professional (CISSP) Practice Exam

The TCP/IP stack utilizes a four-layer model. This model is structured into four distinct layers: the Link layer (also known as the Network Interface layer), the Internet layer, the Transport layer, and the Application layer. Each layer is responsible for different aspects of network communication.

- The Link layer is responsible for the physical transmission of data on the network hardware and provides the means for transferring data between adjacent network nodes.

- The Internet layer facilitates logical addressing and routing of packets across multiple networks, using protocols like IP (Internet Protocol).

- The Transport layer is responsible for end-to-end communication between hosts, ensuring that data is transferred reliably (with TCP) or more efficiently (with UDP).

- The Application layer encompasses the protocols that applications use to communicate over the network.

Understanding this four-layer model is crucial as it underlines how data is encapsulated and transmitted across networks, which is fundamental in systems security practices and protocols. The other choices represent models that do not accurately describe the structure of TCP/IP, such as the two-layer model, which oversimplifies the communication process, or the five-layer model, which adds unnecessary complexity by splitting functionalities that are effectively combined in the TCP/IP model. The three-layer model is also incorrect since it does not capture