Configure TCP/IP - MCSA Windows Server 2012 R2: Installation and Configuration Study Guide - page 420

Understanding IPv6
Internet Protocol version 6 (IPv6) is the first major revamping of IP since RFC 791 was
accepted in 1981. Yes, the operation of IP has improved, and there have been a few bells
and whistles added (such as NAT, for example), but the basic structure is still being used as
it was originally intended. IPv6 has actually been available to use in Microsoft operating
systems since NT 4.0, but it always had to be manually enabled. Windows Vista was
the first Microsoft operating system to have it enabled by default. It is also enabled by
default in Windows 7, Windows 8, Windows Server 2008, Windows Server 2008 R2, and
Windows Server 2012 R2, and it probably will be in all Microsoft operating systems from
this point on.
TCP and UDP—as well as the IP applications, such as HTTP, FTP, SNMP, and the
rest—are still being used in IPv4. So, you might ask, why change to the new version?
What does IPv6 bring to your networking infrastructure? What is the structure of an IPv6
address? How is it implemented and used within Windows Server 2012 R2? I'll answer all
of those questions and more in the following sections.
IPv6 History and Need
In the late 1970s, as the IP specifications were being put together, the vision of the
interconnected devices was limited compared to what we actually have today. To get an
idea of the growth of the Internet, take a look at Hobbes' Internet Timeline in RFC 2235
( www.faqs.org/rfcs/rfc2235.html ). As you can see, in 1984, the number of hosts finally
surpassed 1,000—two years after TCP and IP were introduced. With 32 bits of addressing
available in IPv4, it handled the 1,000+ hosts just fine. And even with the number of hosts
breaking the 10,000 mark in 1987 and then 100,000 in 1989, there were still plenty of IP
addresses to go around. But when the number of hosts exceeded 2 million in 1992 and 3
million in 1994, concern in the industry started to build. So in 1994, a working group was
formed to come up with a solution to the quickly dwindling usable address availability in
the IPv4 space. Internet Protocol next generation (IPng) was started.
Have you heard of IP address depletion being a problem today? Probably not as much.
When the working group realized that it could not have IPv6 standardized before the
available addresses might run out, they developed and standardized Network Address
Translation (NAT) as an interim solution. NAT, or more specifically an implementation of
NAT called Port Address Translation (PAT) , took care of a big portion of the problem.
NAT works very well, but it does have some limitations, including issues of peer-to-
peer applications with their IPv4 addresses embedded in the data, issues of end-to-end
traceability, and issues of overlapping addresses when two networks merge. Because all
devices in an IPv6 network will have a unique address and no network address translation
will take place, the global addressing concept of IPv4 will be brought back (the address put
on by the source device will stay all the way to the destination). Thus, with the new-and-
improved functionality of IPv6, the drawbacks of NAT and the limitations of IPv4 will be
eliminated.