We’ve been hearing for years that the old Internet Protocol
addressing scheme will soon give way to the new and improved “next
generation” of IP: IPv6. Yet most of us are still happily running IPv4
networks. What (if anything) should we be doing to get ready for the big

Let’s take a brief look at the history of IPv6, where it
stands today, why it hasn’t been deployed as quickly as was initially planned,
and why you should nonetheless be planning for the day IPv4 finally ends.
Experts predict that IPv4 should be viable for many years. But you should start
now to understand IPv6 and to ensure that your network is scalable to the new
protocol, particularly if growth rates increase at an unexpected rate.

IPv6: Where did it come from and where is it going?

The Internet is built on the current Internet Protocol,
version 4, which is the “IP” part of TCP/IP. In fact, the functions
performed by IP were originally handled by TCP, which was later split into two
layers and the layer three protocol called IP. RFCs 760 and 791, published in the early 80s, formally
defined the standard characteristics of IP as we know it.

One would assume that an IPv1, v2 and v3 came before IPv4,
but one would be incorrect. IPv4 was the first version of IP, although TCP had
been through three earlier versions (which, as noted, included the
functionality of IP until they were split in v4).

When IP was born, the Internet was a much smaller network.
Its addressing scheme, which uses 32 bit binary addresses that we note in
“dotted decimal” consisting of four octets for human convenience,
seemed much more than adequate. It allows for about 4 billion unique addresses,
and according to the Internet Systems Consortium, there were less than 2000
hosts on the Internet in 1985.

Then the Internet boom of the 90s arrived, and by 1995,
there were over 6 and a half million hosts. It became obvious that the IPv4
address space wasn’t as scalable as originally thought. At that growth rate,
eventually it would simply run out of addresses.

In the 1990s, the push began to develop a new, truly
scalable version of IP. The short-lived IPv5 was only experimental, but IPv6
was soon hailed as the next generation of IP (and sometimes abbreviated IPng). It uses 128-bit addresses, providing a number of
addresses so large it’s usually notated exponentially: 3.4 x 10 to the 38th
power. The real number is 340 undecillion, or 340
with 36 zeroes after it

Why haven’t we already switched?

It seems that IPv6 would solve the address shortage once and
for all. In addition, members of the IETF IPv6 working group, who designed
IPv6, included other improvements in the new protocol, such as security (IPsec encryption). So why haven’t we all switched over by

One reason is that it’s an enormous undertaking. As of
January 2005, ICS reports the number of Internet hosts as over 317 and a half
million. That’s a lot of machines to switch to a whole new addressing system.
And thanks to Network Address Translation (NAT), the IP address shortage has
slowed down even as the number of machines accessing the Internet continues to
increase. NAT allows an entire LAN to access the Internet through a single
public IP address.

On the other hand, the increasing popularity of wireless
devices, including phones, accessing the Internet is revving up the address
crunch again. There’s little doubt that eventually, IPv4 will have to go. But
it could be years before IPv4 is completely replaced. Meanwhile,
what should you be doing about it?

Planning for the IPv6 transition

How do you make your network ready to scale up to IPv6?
Luckily, there are a number of technologies designed to make the transition
easier. Modern operating systems now support IPv6, and the good news is that
the old and new protocols can peacefully coexist. Existing IPv4 systems
(computers, routers and other Internet devices) can still use their v4
addresses after IPv6 is installed.

Some transition mechanisms include:

  • IPv6 over IPv4 tunneling is a
    method which encapsulates the IPv6 packets produced by an upgraded system
    with IPv4 headers. This allows you to send these packets over an IPv4
  • 6to4 tunneling. is
    an address assignment scheme incorporates an IPv4 address to let IPv6
    hosts communicate across an IPv4 network. 6to4 is supported by the IPv6
    implementations in modern operating systems such as Windows Server 2003.
  • IntraSite Automatic Tunnel Addressing Protocol
    (ISATAP) is an address assignment and tunneling technology for
    communication of IPv6 and IPv4 systems on an IPv4 network.
  • Teredo:.is an IPv4 NAT-traversal
    (NAT-T) for IPv6 that allows IPv6 systems behind an IPv4 NAT device to
    communicate on an intranet.

Steps to take

There are several steps involved in preparing for the IPv6
transition. You’ll have to ensure that your applications work independently of
which IP version you use, and you’ll need to upgrade your DNS servers to
support IPv6 because it uses new DNS record types (AAAA and PTR).

The individual computer systems must be upgraded to support
IPv6 (for example, on Windows XP and Server 2003 systems, IPv6 must be
installed as a Network Component via the Network Connections Properties dialog
box) and your routers must be upgraded to support IPv6 protocols along with