What Happened to IPv5?

IPv5 was skipped in favor of IPv6

Visual representation of the internet
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IPv5 is a version of internet protocol (IP) that was never formally adopted as a standard. The "v5" stands for version five of internet protocol. Most computer networks today use version four, typically called IPv4. A new version of IP that is expected become the new worldwide standard is version six, or IPv6.

So what happened to version five? Why the skip from version four to version six? Some people who study computer networking are understandably curious to know what happened to the protocol version in-between, the hypothetical IPv5.

The Fate of IPv5

In short, IPv5 never became an official protocol. Many years ago, what is known as IPv5 started out under a different name: Internet Stream Protocol, or simply ST. ST/IPv5 was developed as a means of streaming video and voice data, and it was experimental, never being transitioned to public use.

IPv5 Address Limitations

IPv5 used IPv4's 32-bit addressing, which eventually became a problem. The format of IPv4 addresses is one you have probably encountered before, in the ###.###.###.### format. Unfortunately, IPv4 is limited in the number of addresses available, and by 2011 the last remaining blocks of IPv4 addresses were allocated. IPv5 would have suffered from the same limitation.

However, IPv6 was developed in the 1990s to solve the addressing limitation, and commercial deployment of this new internet protocol began in 2006.

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

IPv6 Addresses

IPv6 is a 128-bit protocol, and it provides for vastly more IP addresses. While IPv4 offered 4.3 billion addresses (which the rapidly growing internet consumed by the year 2011), IPv6 has the capacity to offer trillions upon trillions of IP addresses (as many as 3.4x1038 addresses) with very little chance of running out anytime soon.