Input (grade 13): The first major version of IP, now referred to as Internet Protocol Version 4 (IPv4) is the dominant protocol of the Internet, although the successor, Internet Protocol Version 6 (IPv6) is in active, growing deployment worldwide.
Output (grade 5): At the moment there are two versions of the Internet Protocol. One is called IP Version 4 (IPv4), the other one is called IP Version 6 (IPv6).