When
the original structure of the Internet was taking shape, an addressing
scheme was formulated to scale to a large number of hosts. From this
thinking came the original design of the Internet Protocol, which
included theoretical support for around 4 billion addresses, or 232.
The thinking at the time was that this would be more than enough
addresses for all hosts on the Internet. This original design gave birth
to the IP address structure that is common today, known as
dotted-decimal format (such as 12.155.166.151). At the time, this
address space filled the addressing needs of the Internet. However, it
was quickly discovered that the range of addresses was inadequate, and
stopgap measures such as Network Address Translation (NAT) were required
to make more efficient use of the available addresses.
In addition to an
inadequate supply of available addresses, the Internet Protocol version 4
(IPv4), as it is known, did not handle routing, IPSec, and QoS support
very efficiently. The need for a replacement to IPv4 was evident.
In the early ’90s, a new
version of the Internet Protocol, known as Internet Protocol version 6
(IPv6), was formulated. This design had several functional advantages to
IPv4, namely a much larger pool of addresses from which to choose by
allowing for 2128 theoretical IP
addresses, or over 340 undecillion, which gives more than enough IP
addresses for every square centimeter on the earth. This protocol is the
future of Internet addressing, and it’s vitally important that an
operating system support it.
Windows Server 2008 R2 comes
with a version of IPv6 installed, and is fully supported as part of the
operating system. Given the complexity of IPv6, it will undoubtedly take
some time before it is adopted widely, but understanding that the
support exists is the first step toward deploying it widely.
Defining the Structure of IPv6
To say that IPv6 is
complicated is an understatement. Attempting to understand IPv4 has been
difficult enough for network engineers; throw in hexadecimal 128-bit
addresses, and life becomes much more interesting. At a minimum,
however, the basics of IPv6 must be understood as future networks will
use the protocol more and more as time goes by.
IPv6 was written to solve
many of the problems that persist on the modern Internet today. The most
notable areas that IPv6 improved upon are the following:
Vastly improved address space—
The differences between the available addresses from IPv4 to IPv6 are
literally exponential. Without taking into account loss because of
subnetting and other factors, IPv4 could support up to 4,294,967,296
nodes. IPv6, on the other hand, supports up to
340,282,366,920,938,463,463,374,607,431,768,211,456 nodes. Even taking
into account IP addresses reserved for overhead, IPv6 authors were
obviously thinking ahead and wanted to make sure that they wouldn’t run
out of space again.
Improved network headers—
The header for IPv6 packets has been streamlined, standardized in size,
and optimized. To illustrate, even though the address is four times as
long as an IPv4 address, the header is only twice the size. In addition,
by having a standardized header size, routers can more efficiently
handle IPv6 traffic than they could with IPv4.
Native support for automatic address configuration— In
environments where manual addressing of clients is not supported or
desired, automatic configuration of IPv6 addresses on clients is
natively built in to the protocol. This technology is the IPv6
equivalent to the Automatic Private Internet Protocol Addressing (APIPA)
feature added to Windows for IPv4 addresses.
Integrated support for IPSec and QoS—
IPv6 contains native support for IPSec encryption technologies and
Quality of Service (QoS) network traffic optimization approaches,
improving their functionality and expanding their capabilities.
Understanding IPv6 Addressing
An IPv6 address, as
previously mentioned, is 128 bits long, as compared with IPv4’s 32-bit
addresses. The address itself uses hexadecimal format to shorten the
nonbinary written form. Take, for example, the following 128-bit IPv6
address written in binary:
111111101000000000000000000000000000000000000000000000000000000000
00001000001100001010011111111111111110010001000111111000111111
The first step in creating the nonbinary form of the address is to divide the number in 16-bit values, as follows:
1111111010000000 0000000000000000
0000000000000000 0000000000000000
0000001000001100 0010100111111111
1111111001000100 0111111000111111
Each 16-bit value is then converted to hexadecimal format to produce the IPv6 address:
FE80:0000:0000:0000:020C:29FF:FE44:7E3F
Luckily, the authors of
IPv6 included ways of writing IPv6 addresses in shorthand by allowing
for the removal of zero values that come before other values. For
example, in the address listed previously, the 020C value becomes simply
20C when abbreviated. In addition to this form of shorthand, IPv6
allows continuous fields of zeros to be abbreviated by using a double
colon. This can only occur once in an address, but can greatly simplify
the overall address. The example used previously then becomes the
following:
FE80:::20C:29FF:FE44:7E3F
Note
It is futile to attempt to
memorize IPv6 addresses, and converting hexadecimal to decimal format is
often best accomplished via a calculator for most people. This has
proven to be one of the disadvantages of IPv6 addressing for many
administrators.
IPv6
addresses operate much in the same way as IPv4 addresses, with the
larger network nodes indicated by the first string of values and the
individual interfaces illustrated by the numbers on the right. By
following the same principles as IPv4, a better understanding of IPv6
can be achieved.
Migrating to IPv6
The migration to IPv6 has
been, and will continue to be, a slow and gradual process. In addition,
support for IPv4 during and after a migration must still be considered
for a considerable period of time. It is consequently important to
understand the tools and techniques available to maintain both IPv4 and
IPv6 infrastructure in place during a migration process.
Even though IPv6 is
installed by default on Windows Server 2008 R2, IPv4 support remains.
This allows for a period of time in which both protocols are supported.
After migrating completely to IPv6, however, connectivity to IPv4 nodes
that exist outside of the network (on the Internet, for example) must
still be maintained. This support can be accomplished through the
deployment of IPv6 tunneling technologies.
Windows Server 2008
R2 tunneling technology consists of two separate technologies. The
first technology, the Intrasite Automatic Tunnel Addressing Protocol
(ISATAP), allows for intrasite tunnels to be created between pools of
IPv6 connectivity internally in an organization. The second technology
is known as 6to4, which provides for automatic intersite tunnels between
IPv6 nodes on disparate networks, such as across the Internet.
Deploying one or both of these technologies is a must in the initial
stages of IPv6 industry adoption.
Making the Leap to IPv6
Understanding a new
protocol implementation is not at the top of most people’s wish lists.
In many cases, improvements such as improved routing, support for IPSec,
no NAT requirements, and so on are not enough to convince organizations
to make the change. The process of change is inevitable, however, as
the number of available nodes on the IPv4 model decreases. Consequently,
it’s good to know that Windows Server 2008 R2 is well prepared for the
eventual adoption of IPv6.
