Introduction
IPv6 (Internet Protocol, version 6) is a replacement protocol for IPv4, which we have today. IPv6 was primarily developed to stave off the impending exhaustion of the IPv4 address pool. IPv4 is a 32 bit binary number, represented in decimal form, such as 204.74.108.1 (which happens to correspond to pdns1.ultradns.net). This 32-bit IPv4 address pool provides approximately 4.2 billion unique addresses that may be used by systems on the Internet. In contrast, IPv6 addresses are 128 bits in length, providing 3.4×1038 addresses (much more than 4.2 billion!).
While there is still much debate in the IETF and broader Internet community about the merits of IPv6 and various deficiencies in the protocol, deployment must eventually happen so everyone should understand the implications of deploying IPv6 a little better.
IPv4 Address Exhaustion
Based on calculations of IPv4 address assignment, experts suggest that we’ll run out of IPv4 address space by 2012. As months go by, many suggest this will happen even sooner. One of the drivers behind doing Network Address Translation (NAT) was to conserve the IPv4 address space. NAT allows multiple private (non-routable) IP addresses to be mapped to a single, routable IP address on the Internet. In addition, address registries developed more strict rules for obtaining dedicated address space. However, many organizations continued to request new, directly allocated address space rather than attempting to conserve existing addresses. They discovered how to take advantage of the system and get their own address space by saying, “I intend to interconnect with two or more ISPs so I need my own address space,” and similar arguments.
One problem that exacerbates address depletion is that many organizations have large pools of addresses that are assigned to them but aren’t used effectively. That is, they have a fairly large pool of addresses but many of them remain unassigned.
While there are some technical limitations with NAT, the fact is that many organizations could simply give back their allocations that aren’t effectively used and utilize private addressing with NAT. But as that is unlikely to happen, and would only forestall IPv4 address depletion for a few years at best, so the world should begin preparing for IPv6.
The problem with adopting IPv6
Note that the standards for IP were written decades ago, when the Internet was much smaller. Suddenly, the address space is increased from 32 bits to 128 bits, so what happens? The IP protocol stack has to be rewritten. It’s embedded in routers, switches, Windows, Linux, OS X, BeOS, mobile phones, you name it. They all have to change. Most network equipment vendors have implemented IPv6 today, but the standards are still not 100% finalized, so interoperability can be sketchy. Some ISPs have upgraded their backbone networks to support IPv6, but in many cases it’s only supported in tunnel mode, meaning it’s wrapped in an IPv4 packet. There aren’t many native IPv6 networks some 15 years after the idea first surfaced.
There are many networks that don’t understand IPv6; some that tunnel through IPv4, and fewer still that natively support IPv6. The real issue is one of economics. Much like DNSSEC, people wonder if the operational expense and headache of converting to IPv6 is worth their time. Customers aren’t demanding it, they don’t care, or they don’t even understand the issue. Further, IPv6 has significant differences from IPv4 that in some cases require staff training, new equipment, new operating systems, or new applications.
Further, there are a number of issues that are still not adequately addressed related to IPv4; some related to security, and some related to fundamental operation in enterprise networks, like DHCPv6.
Conclusion
IPv4 address exhaustion is a reality and will have an impact on the Internet in the very near future. IPv6 is supposed to fix this problem but as I have noted there are issues related to basic enterprise networking and security, as well as operational and economic issues. Still, providers and end users should begin the migration now to get familiar with IPv6 and deal with some of the transition issues before being caught with your “IPv6 shorts” down.
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