IPv6 Transition

There have been many predictions over the years
about IPv6 migration, but the fact is that the IPv4
workarounds that have been developed in the
meantime have been pretty good. It could be that
despite being a superior solution to the address
scarcity issue, IPv6 may never displace IPv4 and its
work-arounds. To underscore this point, look back
at the chart at the beginning of this section. Here
we are in 2007, with only limited deployments of
IPv6, and with many more devices on the Internet
than anticipated back in the late 1990s, but IPv4
keeps chugging along.
Several factors may finally cause the transition—
first as IPv6 “islands” connected with IPv4 networks,
and then finally into end-to-end IPv6 networks.
These factors include the U.S. federal government
mandating that its networks must be IPv6-capable
by a certain date, Microsoft adopting IPv6 into
Windows starting with Vista, and Japan adopting
IPv6 as its country network addressing standard.
At a minimum, it is important for network administrators
and companies to understand IPv6 and its
potential impacts so that they are prepared if and
when the transition occurs. 40

IPv6 Mobility

IPv6 supports a greater array of features for the
mobile user, whether the mobile device is a cell
phone, PDA, laptop computer, or moving vehicle.
Mobile IPv6 (MIPv6) supports a more streamlined
approach to routing packets to and from the
mobile device. It also supports IPsec between the
mobile device and other network devices and hosts.

IPv6 Security

IPv6 has embedded support for IPsec (a common
protocol for encryption). Currently the host operating
system (OS) can configure an IPsec tunnel
between the host and any other host that has IPv6
support. With IPv4 the vast majority of IPsec
deployments are network-based and unknown to
host devices. With IPv6 IPsec, the host could create
an encrypted data connection between itself and
another device on the network. This means that
network administrators do not need to set up the
encryption, because hosts can do it themselves on
demand.

IPv6 Autoconfiguration

IPv4 deployments use one of two methods to
assign IP addresses to a host: static assignment
(which is management-intensive) or DHCP/
BOOTP, which automatically assigns IP addresses
to hosts upon booting onto the network.
IPv6 provides a feature called stateless autoconfiguration,
which is similar to DHCP. Unlike DHCP,
however, stateless autoconfiguration does not
require the use of a special DHCP application or
server when providing addresses to simple network
devices that do not support DHCP (such as robotic
arms used in manufacturing).
Using DHCP, any router interface that has an IPv6
address assigned to it becomes the “provider” of IP
addresses on the network to which it is attached.
Safeguards are built into IPv6 that prevent duplicate
addresses. This feature is called Duplicate
Address Detection. With the IPv4 protocol, nothing
prevents two hosts from joining the network
with identical IP addresses. The operating system
or application may be able to detect the problem,
but often unpredictable results occur.

IPv6 Notation

The first figure demonstrates the notation and
shortcuts for IPv6 addresses.
An IPv6 address uses the first 64 bits in the
address for the network ID and the second 64 bits
for the host ID. The network ID is separated into
prefix chunks. The next figure shows the address
hierarchy.