What Happened to IPv5?

IPv5 was skipped in favor of IPv6

An internet protocol is the set of rules that govern how information packets are transmitted over a network. IPv5 is a version of Internet Protocol (IP) that was never formally adopted as a standard. The v5 stands for version 5 of the Internet Protocol. Computer networks use version 4, typically called IPv4, or a newer version of IP called IPv6.

Visual representation of the internet
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IPv5 Address Limitations

IPv5 never became an official protocol. What is known as IPv5 started out under a different name: ​Internet Stream Protocol, or simply ST.

The ST/IPv5 internet protocol was developed as a means of streaming video and voice data by Apple, NeXT, and Sun Microsystems, and it was experimental. ST was effective at transferring data packets on specific frequencies while maintaining communication.

It would eventually serve as a foundation for the development of technologies like Voice over IP, or VoIP, which is used for voice communications over the internet.

32-Bit Addressing

With the development of IPv6 and its promise of nearly unlimited IP addresses and a fresh start for the protocol, IPv5 was never transitioned to public use in large part because of its 32-bit limitations.

IPv5 used IPv4's 32-bit addressing, which eventually became a problem. The format of IPv4 addresses is the ###.###.###.### format, which is made up of four numerical octets (a unit of digital information in computing consisting of eight bits), with each set ranging from 0 to 255 and separated by periods. This format allowed for 4.3 billion internet addresses; however, the rapid growth of the internet soon exhausted this number of unique addresses.

By 2011, the last remaining blocks of IPv4 addresses were allocated. With IPv5 using the same 32-bit addressing, it would have suffered from the same limitation.

So, IPv5 was abandoned before ever becoming a standard, and the world moved on to IPv6.

IPv6 Addresses

IPv6 was developed in the 1990s to solve the addressing limitation, and commercial deployment of this new internet protocol began in 2006. IPv6 is a 128-bit protocol, and it provides more IP addresses.

The format of IPv6 is a series of eight 4-character hexadecimal numbers; each of these represents 16 bits, for a total of 128 bits. The characters in an IPv6 address are numbers from 0 to 9 and letters from A to F.

The IPv6 Format

An example of an IPv6 address is 2001:0db8:0000:0000:1234:0ace:6006:001e. IPv6 has the capacity to offer trillions upon trillions of IP addresses (as many as 3.4x1038 addresses) with little chance of running out.

The format of an IPv6 address is long and often contains numerous zeros. Leading zeros in the address can be suppressed to shorten addresses. For example, the above IPv6 address may be expressed as the much shorter 2001:db8::1234:ace:6006:1e. Also, when there is a series of more than one 4-character set that consists of all zeros, these may be replaced with the "::" symbol.

Only one :: symbol can be used in an IPv6 address.

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