The Application Layer of the TCP/IP model contains protocols used for process-to-process communications across an IP network and is the top most layer of the TCP/IP model. FTP (File Transfer Protocol - Option 1), HTTP (Hyper Text Transfer Protocol - Option 2), and DNS (Domain Name System - Option 3) are all application layer protocols. They provide services directly to user applications.

On the other hand, the IP (Internet Protocol - Option 4) is part of the Internet Layer, which is the second layer in the TCP/IP model. The primary protocols in this layer are IP (responsible for the delivery of datagrams) and ICMP (Internet Control Message Protocol). Therefore, the correct answer is indeed IP (Option 4), because it is not an application layer protocol in the TCP/IP model.