1. (ULP, or upper-layer protocol) Any protocol residing in OSI layers five or above.
The Internet protocol suite includes many upper layer protocols representing a wide variety of applications e.g. FTP, NFS, RPC, and SMTP. These and other network applications use the services of TCP/IP and other lower layer protocols to provide users with basic network services.
2. A protocol higher in the OSI reference model than the current reference point. Upper Layer Protocol is often used to refer to the next-highest protocol in a particular protocol stack.