Understanding IPv6
Internet Protocol version 6 (IPv6) is a network layer that is designed to overcome
shortcomings of the original Internet Protocol, IPv4. (That’s right; the first version was
dubbed IPv4, and the second version is IPv6.) The most significant difference is the
much larger address space. The 32-bit IPv4 addressing scheme provides for a theoretical
maximum of approximately 4 billion unique addresses, which seemed like a lot
when the internet and Internet Protocol were conceived nearly three decades ago.
(Because of the way IP addresses are allocated, the actual number in use is far less.) As a
stopgap measure to overcome the limited number of IP addresses, private IP addresses
and Network Address Translation were implemented, because this system allows a large
number of computers to share a single public IP address.
There will be no shortage of addresses with IPv6, which uses 128-bit addresses—providing
a pool of 3.4 × 1038 addresses. (That’s over 50 octillion addresses for every
person on earth. Not many people have that many computers and other electronic
devices, each of which will ultimately be reachable by its IPv6 address.)
Although NAT has been promoted as a security measure that shields networked computers
behind a NAT firewall from external attack—which it does reasonably well—the
security benefit was largely an afterthought; its real raison d’être is to ease the address
shortage. IPv6 brings true security improvements, achieving the long-sought goal of
security implemented at the network layer level; standards-based Internet Protocol
security (IPsec) support is part of every IPv6 protocol suite.
Other improvements in IPv6 include easier configuration and more efficient routing.
Unfortunately, although IPv6 is being rapidly rolled out in many Asian countries, its
adoption in the West is likely to take many years. Full implementation requires not only
support at the host operating system—which we now have in Windows 7, Windows
Server 2008, and other recent versions of Windows—but application and hardware
support as well, including the routers that tie together the various nodes of the internet
and the firewalls that keep them apart. Replacing the existing hardware (not just
routers, but also printers and other network-connected devices) and other infrastructure
will require huge investment and much time.
Until the transition to IPv6 is complete many years hence, you can gain several of its
benefits with Windows 7. Today, computers running Windows 7 can communicate over
IPv4 and IPv6 networks at the same time. This means that if your local area network
(or your ISP) supports IPv6, Windows will use it because IPv6 is the primary protocol in
Windows 7. You can also access IPv6 websites and other resources even if the intervening
network infrastructure doesn’t support IPv6, because Windows will automatically
fall back to a tunneling system such as Teredo. (Teredo is an IPv6 transition technology
that allows end-to-end communication using IPv6 addresses; NAT translation tables on
Teredo client computers allow it to communicate through routers that use NAT. Other
tunneling systems effectively embed IPv6 data in IPv4 packets.)
While you wait for the transition to IPv6 to be complete, you can find plenty of
detailed information about IPv6 at the Microsoft IPv6 website, microsoft.com/ipv6. And
if you really want the details, we recommend Understanding IPv6, Second Edition, by
Joseph Davies (Microsoft Press, 2008).
