IP versions
There are two versions of the Internet Protocol (IP): IP version 4 (IPv4) and IP version 6 (IPv6). The gap in version sequence between IPv4 and IPv6 resulted from the assignment of number 5 to the experimental Internet Stream Protocol in 1979, which was never referred to as IPv5.
IPv4 addresses
Main article: IPv4 ยง Addressing
Decomposition of an IPv4 address from dot-decimal notation to its binary value.
An IP address in IPv4 is 32-bits in size, which limits the address space to 4294967296 (232) IP addresses. Of this number, IPv4 reserves some addresses for special purposes such as private networks (~18 million addresses) or multicast addresses (~270 million addresses).
IPv4 addresses are usually represented in dot-decimal notation, consisting of four decimal numbers, each ranging from 0 to 255, separated by dots, e.g., 172.16.254.1. Each part represents a group of 8 bits (octet) of the address. In some cases of technical writing, IPv4 addresses may be presented in various hexadecimal, octal, or binary representations.