Which one of the following protocols is not an application layer of the TCP/IP model?

In the TCP/IP model, the Application Layer is the topmost layer that provides network services directly to end-users and software applications. Common protocols operating at this layer include the File Transfer Protocol (FTP) for file sharing, HyperText Transfer Protocol (HTTP) for web browsing, and the Domain Name System (DNS) for resolving domain names to IP addresses. These protocols facilitate user-level tasks like email, remote login, and resource sharing. In contrast, the Internet Protocol (IP) is a core protocol of the Internet (or Network) Layer. Its primary function is to provide addressing and routing mechanisms for delivering data packets across different networks, rather than interacting directly with user applications. Therefore, while FTP, HTTP, and DNS are application layer protocols, IP belongs to the lower network layer of the TCP/IP stack.