Which of the following is the correct top-to-bottom order of the TCP/IP model layers?

• A. Application, Transport, Internet, Network Access
• B. Network Access, Internet, Transport, Application
• C. Internet, Transport, Network Access, Application
• D. Application, Internet, Transport, Network Access

Answer: (A)

The top-to-bottom order of the TCP/IP model layers is Application, Transport, Internet, Network Access. The Application layer sits at the top because it’s where user-facing protocols (like HTTP, SMTP, or DNS) interact with applications. The Transport layer below it provides end-to-end communication services (TCP or UDP) and handles things like segmentation and reliability. The Internet layer underneath manages addressing and routing (IP). The bottom Network Access layer covers the actual networking hardware and data-link/physical details, i.e., how frames are transmitted on the local network. This stack order reflects how data is encapsulated as it moves down the stack and how it would be decapsulated as it moves up, from application data to frames on the wire and back. Other options misplace these layers, placing the bottom or core routing layer in the wrong position, which doesn’t match how the protocol stack actually stacks and processes data.