Every device that communicates with others on a network must have a unique Media Access Control (MAC) address similar to a fingerprint, and a common way to communicate, such as the Transmission Control Protocol/Internet Protocol (TCP/IP) used on the Internet. The current protocol, version 4 (IPv4), consists of four blocks of numbers ranging from 0 to 255, separated by a period, for example: 012.032.090.026 (but it can also be written as 126.96.36.199 by leaving off the leading zeros). Each time a number changes in any block, it becomes a new and unique IP address.
A network router's job is to track and store the path of IP addresses through the network, as well as assigning names to IP addresses. The number of potential IP addresses is more than 4 billion, or 4,294,967,296 to be exact, since there are 256 possible values (from 0 to 255) for each of the four blocks. (For the math-challenged, that's 256 x 256 x 256 x 256 or 2564.) This seems like a lot of addresses, but not all the addresses are useable, and those that are were assigned to Internet service providers in blocks, so many go unassigned and wasted. With an ever-increasing number of people using the Internet, the available IP addresses are quickly running out.
The second version of the Internet Protocol to be formally adopted for general use, version 6 (IPv6), should fix the shortage problem well into the future, allowing cell phones, other mobile devices and even home appliances to have their own IP address. IPv6 addresses will consist of eight groups of four hexadecimal digits, for a total of 32 hexadecimal digits. Because hex notation offers 16 possible values per digit (since it adds the first six letters of the alphabet to the 10 digits, 0–9), there are 16³² possible IPv6 addresses. This number, which is more than 340 followed by 36 zeros, is approximately seven-fold greater than the total number of atoms that comprise the sum of every human being on the planet. Each block of four hex digits will be separated by a colon in the IPv6 addressing scheme; an example of an IPv6 address would be 2001:0db8:85a3:0000:1319:8a2e:0370:7344. In this address scheme, the first four blocks represent the network prefix, and the last four blocks represent the host (often generated from the MAC address).
Unfortunately, any networking hardware or software designed before this change cannot recognize the new IPv6 addressing.
When will this change take place? There is no fixed target date for IPv6 adoption or compliance. But the U.S. Department of Defense and other federal agencies have mandated that all backbone systems be IPv6-compliant by mid-2008. Several foreign countries, including Japan and Germany, have major IPv6 initiatives under way and are progressing toward IPv6 compliance by 2007. Although IPv6 was adopted by the Internet Engineering Task Force 12 years ago, only a small percentage of live addresses now use it.
This sounds like Y2K, but that turned out to be a minor issue. Since there is no hard global cutover date for IPv6, the impact is not fixed on one day, such as Jan. 1, 2000. In many cases, manufacturers have produced patches or updates to resolve the problem. Others may be protected by devices that translate between the old and new standards, using a protocol called Network Address Translation. Companies that take advantage of the added security and other advantages that IPv6 will offer will need to remove older networking gear. Eventually, all networks will have to make the switch — much like the ongoing transition to digital TV. (Traditional analog television transmission is currently scheduled to end in early 2009.)