Will IPv6 break my internet on old machines?

IP? v4? v6?

First, let's remove some mystery. "IP" is the IP in TCP/IP, and stands for Internet Protocol - the basic language of machines and devices communicating with each other. V4 simply indicates that this is the fourth version of the protocol.

In IPv4, each device connected to a network is uniquely identified by a number between zero and four billion. OK, not exactly zero and four billion, because some numbers are reserved, but you get the idea.

That's the number that you often see expressed as four smaller numbers separated by periods. For example, the IP address of the server hosting Ask Leo! on the internet is today 67.225.235.59. I say today because it's been different in the past and could change tomorrow. That's why you use the address ask-leo.com to get to the site, not the IP address.

There was a time when four billion seemed like more than enough, yet current estimates are that we will run out sometime in 2012.

As a result, IPv6 changes the addressing scheme to be four times bigger. No, not four times four billion, but rather four billion raised to the fourth power.

Put another way, with IPv6, we could theoretically have 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses on the internet.

What happens when we run out of IPv4?

Not a lot, really. If we run out, then it becomes more difficult to put more machines directly on the internet. All of the existing machines, servers, and services could keep on running as they did before, and more machines could always be connected via NAT routers, as you probably do today.

There just wouldn't be any room to add more directly to the internet. That's where some of these "The Internet Is Full" headlines have come from.

So, what that means to you is ... well, not much. For the most part, things will just keep working even after we run out.

The internet and the services you use today will continue to support IPv4 for many, many years. The lack of IPv4 addresses simply makes it more difficult to add new resources to the internet that everyone can reach.

The Transition to IPv6

It's important to realize that switching to IPv6 is a process, not an event. In fact, it's a process that has been underway for years already; one that will continue for many more years into the future.

The majority of the internet's infrastructure can already handle both IPv4 and IPv6 simultaneously.

Most of the work is left at the endpoints - the servers that you find on the web, and the machines like yours and mine that use them.

As you've seen, most new operating systems are ready for IPv6. Windows XP, Vista, and Windows 7 all either include or have available IPv6 networking support. Most current versions of Linux and Mac OS also support IPv6.

The largest remaining piece of work is in between: the millions of modems and routers in homes and businesses that aren't quite ready for IPv6, and the actual assignment of IPv6 addresses in addition to IPv4. That'll take some time.

This summer, several of the major internet services are getting together to test IPv6 just for that reason. World IPv6 day is a test where sites like Google will support IPv6 for 24 hours as a test.

Your Computer Won't Break

If you can't upgrade your computer or your internet connection, your machine won't break ... at least, not for a while.

There are a hand full of scenarios where it could:

• The remote resource became an IPv6 only resource. If reallybigbookstore.com someday decided to release it's IPv4 address and only have an IPv6 address, then IPv6 would be required to access it. As you can imagine, that wouldn't be a very smart move on the part of reallybigbookstore.com. The vast majority of the sites and services you use today will continue to use IPv4 in addition to IPv6 as long as is possible.

• Some equipment between your computer and whatever site you're attempting to access decides to go IPv6 only and no longer carry IPv4 traffic. This is actually pretty unlikely until the very end of IPv4 use, as it'll break a lot of communication attempts. Again, the equipment that carries traffic around the internet will continue to support IPv4 as long as possible.

• Your equipment is IPv6 capable, but misconfigured.

In short, I truly believe that the average consumer won't notice much for a very long time. Things will continue to work. Eventually, your ISP will give you an upgraded modem that will support IPv6. The next router switch or hub that you purchase will also very likely support IPv6 as well.

Someday...

Someday, the majority of sites and services that you use will all support IPv6 in addition to IPv4.

Someday, when setting up a new internet connection, your ISP will just give you IPv6 equipment and an IPv6 address.

Someday, your ISP will ask you to upgrade the modem or router on your existing internet connection.

Someday, websites and the internet will stop supporting IPv4.

It's only when that last someday happens that your old devices that can't support IPv6 will start to have problems.

And that day is years away.