Every computer system and device connected to the Internet is located by an IP address. The current system of distributing IP addresses is called IPv4. This system assigns each computer a 32-bit numeric address, such as 126.96.36.199. However, with the growth of computers connected to the Internet, the number of available IP addresses are predicted to run out in only a few years. This is why IPv6 was introduced.
IPv6, also called IPng (or IP Next Generation), is the next planned version of the IP address system. (IPv5 was an experimental version used primarily for streaming data.) While IPv4 uses 32-bit addresses, IPv6 uses 128-bit addresses, which increases the number of possible addresses by an exponential amount. For example, IPv4 allows 4,294,967,296 addresses to be used (2^32). IPv6 allows for over 340,000,000,000,000,000,000,000,000,000,000,000,000 IP addresses. That should be enough to last awhile.
Because IPv6 allows for substantially more IP addresses than IPv4, the addresses themselves are more complex. They are typically written in this format:
Each "hhhh" section consists of a four-digit hexadecimal number, which means each digit can be from 0 to 9 and from A to F. An example IPv6 address may look like this:
Because IPv6 addresses are so complex, the new system also adds extra security to computers connected to the Internet. Since there are so may IP address possibilities, it is nearly impossible to guess the IP address of another computer. While most computer systems today support IPv6, the new Internet procotol has yet to be fully implemented. During this transitional process, computers are often assigned both an IPv4 and an IPv6 address. By 2008, the U.S. government has mandated that all government systems use IPv6 addresses, which should help move the transition along.