How many layers are in the TCP/IP model, and what are they called?

• A. Three layers: Link, Network, Application.
• B. Four layers: Link, Internet, Transport, and Application.
• C. Six layers: Access, Link, Internet, Transport, Session, Application.
• D. Five layers: Physical, Data Link, Network, Transport, Application.

Answer: (B)

Four layers define the TCP/IP model: Link, Internet, Transport, and Application. Each layer handles a distinct set of tasks: the Link layer deals with accessing the local network and how devices on the same physical or data-link segment communicate; the Internet layer provides logical addressing and routing so data can travel between networks; the Transport layer offers end-to-end delivery, reliability, and flow control using protocols like TCP or UDP; and the Application layer encompasses the protocols software uses to interact over the network (such as HTTP, DNS, FTP). This four-layer structure is a practical, widely taught framework for the TCP/IP suite, and it contrasts with OSI’s seven-layer model by consolidating several functions into fewer layers.

The other options don’t fit because they either omit a layer essential for end-to-end communication (the Transport layer), introduce layers that OSI uses but TCP/IP does not (such as a separate Session layer), or split the Link into Physical and Data Link, which TCP/IP groups under a single Link layer. In short, the correct arrangement reflects four layers named Link, Internet, Transport, and Application.