Combining Encapsulation Layers in TCP/IP Application Layer

ACD

The TCP/IP protocol suite was developed before the OSI model, and as a result, it doesn't precisely fit into the OSI model's layering structure. However, the TCP/IP protocol suite is generally mapped to the OSI model's layers as follows:

• The application layer combines the functionality of the OSI model's Session, Presentation, and Application layers.
• The transport layer corresponds to the OSI model's Transport layer.
• The Internet layer maps to the OSI model's Network layer.
• The network access layer maps to the OSI model's Data Link and Physical layers.

Therefore, the correct answer to the question is A. Session, C. Presentation, and D. Application.

The Session layer of the OSI model provides services that coordinate communication between applications. It establishes, maintains, and terminates communication sessions and manages the exchange of data between the applications. In the TCP/IP protocol suite, this functionality is combined with the Presentation and Application layers into the Application layer.

The Presentation layer of the OSI model provides services for formatting and presenting data to the application layer. This includes data encryption, compression, and conversion to a standard format. In the TCP/IP protocol suite, this functionality is also combined with the Session and Application layers into the Application layer.

The Application layer of the OSI model provides services to applications for network communication. This includes protocols for email, file transfer, and remote access. In the TCP/IP protocol suite, this layer combines the functionality of the Session and Presentation layers with the Application layer.

The Transport layer of the OSI model provides services for reliable and efficient data transfer between hosts. This includes segmenting data into manageable units, flow control, and error recovery. In the TCP/IP protocol suite, this layer corresponds to the Transport layer.

The Network layer of the OSI model provides services for routing and forwarding data between hosts. This includes addressing and identifying hosts, as well as choosing the best path for data transmission. In the TCP/IP protocol suite, this layer corresponds to the Internet layer.