It is often said, "the Internet is running out of phone numbers," as a way to express that the Internet is running out of IPv4 addresses, to those who are unfamiliar with Internet technologies. IPv4 addresses, like phone numbers are assigned hierarchically, and thus, have inherent inefficiency. The world’s Internet population has been growing and the number of Internet-connected devices continues to rise, with no end in sight. In the next week, the American Registry for Internet Numbers (ARIN) will have exhausted their supply of IPv4 addresses. The metaphorical IPv4 cupboards are bare. This long-predicted Internet historical event marks opening a new chapter of the Internet’s evolution. However, it is somehow anti-climactic now that this date has arrived. The Internet will continue to operate, but all organizations must now accelerate their efforts to deploy IPv6.

ARIN IPv4 Address Exhaustion

The Internet Assigned Numbers Authority (IANA) delegates authority for Internet resources to the five RIRs that cover the world. The American Registry for Internet Numbers (ARIN) is the Regional Internet Registry (RIR) for the United States, Canada, the Caribbean, and North Atlantic islands. ARIN has been managing the assignment of IPv4 and IPv6 addresses and Autonomous System (AS) numbers for several decades. Each RIR has been managing their limited IPv4 address stores and going through their various phases of exhaustion policies. ARIN has been in Phase 4 of their IPv4 depletion plan for more than a year now. ARIN will soon announce that they have completely extinguished their supply of IPv4 addresses.

At this point, the rules for how address resources are allocated will change. Address resource applicants may not get their justified request fulfilled and might be offered a smaller block or the choice to be added to a waiting list. This page documents the process for the waiting list for unmet IPv4 address requests. To review the unmet resource policies, consult the Number Resource Policy Manual (NRPM), check out section 4.1.8. However, when the supply of IPv4 address space drops to 0.00000, then there will be no more addresses to allocate. If IPv4 addresses become available, then the policies in the NRPM will dictate that they are given out based on the Waiting List for Unmet Requests method.

IPv4 Exhaustion Predicted for Decades

Predictions of IPv4 depletion date back to the early 1990s. The IETF formed the Address Lifetime Expectations (ALE) Working Group in the mid-1990s to analyze the rate of IPv4 adoption in anticipation that this date would come. IPv4 address supply concerns was the primary reasons the IETF wanted to create a new version of the Internet Protocol (IP). The IETF IP Next Generation (IPng) working group started their work around that time and the first IPng was drafted around 1993. In those early days of the Internet, no one could have predicted the tremendous growth of the Internet. The IETF created Internet Protocol version 6 and finalized the header format with RFC 2460 in 1998. Each year as the IPv4 Internet grew at breakneck speeds, transition to IPv6 had become more and more daunting.

Prolonging IPv4’s Lifespan

As the Internet began to grow, techniques like Classless Interdomain Routing (CIDR) and Network Address Translation (NAT) were used to extended life-support for IPv4 for almost two decades. Now ISPs are looking at using Carrier Grade NAT (CGN)/Large Scale NAT (LSN) to further prolong the use of IPv4. However, many of these multi-NAT techniques cause problems for many popular Internet applications. We can expect that there will be other techniques contrived to keep the much-loved IPv4 protocol running for decades to come.

No End in Sight for IPv4

Few organizations are thinking about when they may eventually stop using IPv4. Some enterprise organizations have not given IPv6 much thought and are not aggressively moving to implementing it. Organizations will not be able to transition right from using IPv4 to using IPv6 directly. The dual-stack transition technique is the dominant transition strategy (tunnels are to be avoided when possible). In other words, organizations are encouraged to use native IPv6.

Even if an organization starts to deploy IPv6 immediately, they will still require the use of IPv4 for years to come. IPv6 may not have a large impact on an organization’s near-term IPv4 address constraints. Those few enterprise organizations are playing a dangerous "game of chicken" by ignoring IPv6. While, there are techniques for prolonging the lifespan of IPv4, organizations may end up with limited options. Going forward, organizations that require additional IPv4 addresses will need to request them from their service provider (provided they have any addresses left to lease) or purchase them on the open market. As IPv4 address blocks get traded around and split up, we can expect the Internet routing tables to become increasingly fragmented.

Organizations that deploy IPv6 will be living in a dual-stack world for many years. During that period of using both IPv4 and IPv6 in parallel, organizations will likely incur increased operating expenses. Gradually, over time, the cost of running an IPv4 network will increase.

Now What? Move to IPv6!

So now that this Internet historic date of ARIN’s IPv4 run-out has arrived, we should review what our own organizations are doing to plan for the next phase of the Internet’s lifespan.

Internet Service Providers (ISPs) should already be well on their way through their IPv6 deployments. If you work for an ISP that has not yet started your IPv6 deployment then you are in serious danger of falling far behind your competitors.

If you are an enterprise organization, then your plans for the future need to be quickly defined and put into action. Your organization no longer has the option to continue to ignore IPv6. However, your organization may be planning to invest in purchasing additional IPv4 addresses. Your organizations will be forced to tolerate the use of multiple-layers of NAT and the application problems that come with it. Your organization will be forced to invest in larger Internet routers to be able to handle the rapidly expanding IPv4 Internet routing tables. Your organization should be planning for future years of legacy IPv4-Internet connectivity and actively moving toward full deployment of IPv6.

If your organization is one of those that waited to embrace IPv6, then you are in luck, as there are plenty of resources available to help you with your IPv6 planning and deployment. While Wikipedia.org can get you started learning the basics, you should visit the Internet Society Deploy360 Programme IPv6 page. You should also explore ARIN’s own Get6 site. We wish you the best of luck configuring your systems so you can reach the "whole Internet" using IPv6 and not just the "old Internet" using IPv4.