IPv6: An introduction

The Internet is running out of addresses.  Current projections indicate the last available blocks will be assigned to regional registrars in May of next year, and that pool will be exhausted in January of 2012.  Clearly, there should be some urgency to begin the move to IPv6, but many sites appear to be in no hurry.  This generally seems to be due to the questions surrounding the 4-to-6 transition, which is why Rudi van Drunen's new IPv6 course was filled to capacity.

The first part of the course focused on some of the differences between IPv4 and IPv6.  Apart from the fact that IPv6 has many times the number of addresses, there are other technical changes.  For instance, IPv6 has a simplified header, reducing the number of fields from 12 to 8.  However, due to the longer source and destination addresses, the IPv6 header is twice the 20-byte length of its predecessor.

In addition to the under-the-hood changes, there are differences that require a change in the thoughts and habits of both administrators and programmers.  One potentially annoying change is that the 128-bit address length will make the memorization of IP addresses very difficult.  DNS will be even more critical in the IPv6 world.

A more interesting paradigm shift is the loss of NAT.  For better or for worse, sites both large and small have used NAT not only as a way to expand their available address space, but also to provide some degree of pseudo-firewall.  In some places, especially in the consumer universe, the wireless router is all that prevents outside traffic from reaching hosts.  The default routing configuration of IPv6-supporting consumer grade routers will be a key factor in how secure home users will be.

In addition to hardware and OS support, application-level support of IPv6 is another factor in the adoption process.  Network-aware applications that do any parsing or processing of IP addresses will need to have IPv6 support added.

There are clearly many factors that help explain why IPv6 uptake has been so slow.  Monday's tutorial helped to clear up some of the confusion, although it didn't necessarily encourage everyone.  Twitter user @jrwoodman said "aside from the magic factor, I no longer fear implementing IPv6 on a trial-to-production basis."  However, one attendee commented in the chat that he "

need[s] to find some new gig before IPv4 runs out because [he] honestly hate[s] this protocol."

For those who remain uncertain about IPv6, LISA 10 offers several more opportunities this week.  An Invited Talks session at 11am Wednesday focuses on IPv6, and on Thursday at 11am, a Practice and Experience report focuses on IPv6 at ARIN.  At 2pm on Thursday, The (IPv6) Guru is In.

If you're ready to start implementing IPv6, Rudi has given the following homework assignments:

• Get a tunnel and a subnet to use over the tunnel
• Set up the firewall and subnet autoconfiguration
• Turn on IPv6
• Adapt DNS to support IPv6
• Get native IPv6 from your ISP

The first three steps should be done by the end of this year, Rudi suggests, with the last two done by the end of 2012.  This way, you'll be ready for IPv6 before the last of the IPv4 address space gets assigned.