I just read the WordPress article about World IPv6 Day, and many of the comments in response expressed that they only had a very basic understanding of what an IPv6 Internet address actually is. To better explain this issue, we have provided a 10-point FAQ that should help clarify in simple terms and analogies the ramifications of transitioning to IPv6.

To start, here’s an overview of some of the basics:

Why are we going to IPv6?

Every device connected to the Internet requires an IP address. The current system, put in place back in 1977, is called IPv4 and was designed for 4 billion addresses. At the time, the Internet was an experiment and there was no central planning for anything like the commercial Internet we are experiencing today. The official reason we need IPv6 is that we have run out of IPv4 addresses (more on this later).

Where does my IP address come from?

A consumer with an account through their provider gets their IP address from their ISP (such as Comcast). When your provider installed your Internet, they most likely put a little box in your house called a router. When powered up, this router sends a signal to your provider asking for an IP address. Your provider has large blocks of IP addresses that were allocated to them most likely by IANI.

If there are 4 billion IPv4 addresses, isn’t that enough for the world right now?

It should be considering the world population is about 6 billion. We can assume for now that private access to the Internet is a luxury of the economic middle class and above. Generally you need one Internet address per household and only one per business, so it would seem that perhaps 2 billion would be plenty of addresses at the moment to meet the current need.

So, if this is the case, why can’t we live with 4 billion IP addresses for now?

First of all, industrialized societies are putting (or planning to put) Internet addresses in all kinds of devices (mobile phones, refrigerators, etc.). So allocating one IP address per household or business is no longer valid. The demand has surpassed this considerably as many individuals require multiple IP addresses.

Second, the IP addresses were originally distributed by IANI like cheap wine. Blocks of IP addresses were handed out in chunks to organizations in much larger quantities than needed. In fairness, at the time, it was originally believed that every computer in a company would need its own IP addresses. However, since the advent of NAT/PAT back in the 1980s, most companies and many ISPs can easily stretch a single IP to 255 users (sharing it). That brings the actual number of users that IPv4 could potentially support to well over a trillion!

Yet, while this is true, the multiple addresses originally distributed to individual organizations haven’t been reallocated for use elsewhere. Most of the attempted media scare surrounding IPv6 is based on the fact that IANI has given out all the centrally controlled IP addresses, and the IP addresses already given out are not easily reclaimed. So, despite there being plenty of supply overall, it’s not distributed as efficiently as it could be.

Can’t we just reclaim and reuse the surplus of IPv4 addresses?

Since we just very recently ran out, there is no big motivation in place for the owners to give/sell the unused IPs back. There is currently no mechanism or established commodity market for them (yet).

Also, once allocated by IANI, IP addresses are not necessarily accounted for by anyone. Yes, there is an official owner, but they are not under any obligation to make efficient use of their allocation. Think of it like a retired farmer with a large set of historical water rights. Suppose the farmer retires and retains his water rights because there is nobody to which he can sell them back. The difference here is that water rights are very valuable. Perhaps you see where I am going with this for IPv4? Demand and need are not necessarily the same thing.

How does an IPv4-enabled user talk to an IPv6 user?

In short, they don’t. At least not directly. For now it’s done with smoke and mirrors. The dirty secret with this transition strategy is that the customer must actually have both IPv6 and IPv4 addresses at the same time. They cannot completely switch to an IPv6 address without retaining their old IPv4 address. So it is in reality a duplicate isolated Internet where you are in one or the other.

Communication is possible, though, using a dual stack. The dual-stack method is what allows an IPv6 customer to talk to IPv4 users and IPv6 users at the same time. With the dual stack, the Internet provider will match up IPv6 users to talk with IPv6 if they are both IPv6 enabled. However, IPv4 users CANNOT talk to IPv6 users, so the customer must maintain an IPv4 address otherwise they would cut themselves off from 99.99+ percent of Internet users. The dual-stack method is just maintaining two separate Internet interfaces. Without maintaining the IPv4 address at the same time, a customer would isolate themselves from huge swaths of the world until everybody had IPv6. To date, in limited tests less than .0026 percent of the traffic on the Internet has been IPv6. The rest is IPv4, and that was for a short test experiment.

Why is it so hard to transition to IPv6? Why can’t we just switch tomorrow?

To recap previous points:

1) IPv4 users, all 4 billion of them, currently cannot talk to new IPv6 users.

2) IPv6 users cannot talk to IPv4 users unless they keep their old IPv4 address and a dual stack.

3) IPv4 still works quite well, and there are IPv4 addresses available. However, although the reclamation of IPv4 addresses currently lacks some organization, it may become more econimically feasible as problems with the transition to IPv6 crop up. Only time will tell.

What would happen if we did not switch? Could we live with IPv4?

Yes, the Internet would continue to operate. However, as the pressure for new and easy to distribute IP addresses for mobile devices heats up, I think we would see IP addresses being sold like real estate.

Note:  A bigger economic gating factor to the adoption of the expanding Internet is the limitation of wireless frequency space. You can’t create any more frequencies for wireless in areas that are already saturated. IP addresses are just now coming under some pressure, and as with any fixed commodity, we will see their value rise as the holders of large blocks of IP addresses sell them off and redistribute the existing 4 billion. I suspect the set we have can last another 100 years under this type of system.

Is it possible that a segment of the Internet will split off and exclusively use IPv6?

Yes, this is a possible scenario, and there is precedent for it. Vendors, given a chance, can eliminate competition simply by having a critical mass of users willing to adopt their services. Here is the scenario: (Keep in mind that some of the following contains opinions and conjecture on IPv6, the future, and the motivation of players involved in pushing IPv6.)

With a complete worldwide conversion to IPv6 not likely in the near future,  a small number of larger ISPs and content providers turn on IPv6 and start serving IPv6 enabled customers with unique and original content not accessible to customers limited to IPv4. For example, Facebook starts a new service only available on their IPv6 network supported by AT&T. This would be similar to what was initially done with the iPad and iPhone.

It used to be that all applications on the Internet ran from a standard Web browser and were device independent. However, there is a growing subset of applications that only run on the Apple devices. Just a few years ago it was a forgone conclusion that vendors would make Web applications capable of running on any browser and any hardware device. I am not so sure this is the case anymore.

When will we lose our dependency on IPv4?

Good question. For now, most of the push for IPv6 seems to be coming from vendors using the standard fear tactic. However, as is always the case, with the development of new products and technologies, all of this could change very quickly.