IPv6 adoption vs IPv4

So far IPv6 has managed to grab only a
small part of the Internet pie, but there's plenty of action happening in the
background to make the existing Internet infrastructure ready for it. Will the
Internet ever shift to the new protocol anytime soon? Let's take a look.

The original intention for designing IPv6 was that the
available IP address range in IPv4 was running out quickly. There were just not
enough IP addresses in IPv4 to give to everybody. In fact, even the distribution
of IPv4 addresses globally was skewed, with a major portion of them allotted to
the US and Europe and a small part to Asia Pacific countries. With Internet
connectivity growing rapidly in these countries, this skew will have its effect.
Even otherwise, the distribution is inefficient with many companies sitting with
lots of unused blocks of IP addresses. IPv4 countered both these problems for
more IP addresses by devising Network Address Translation or NAT technology.
This needs no introduction, as most organizations already use it to allow
machines on their network to share an IP address and access the Internet. But
NATing has only slowed down the adoption of IPv6 for some time. It's not going
to stop it completely.

The thirst for more IP addresses is much bigger and
increasing. Consider the mobile revolution that's currently happening
globally.  So many digital devices
like cellphones, PDAs, smartphones, etc have become available today. Most of
these can connect to the Internet, and therefore need an IP address. There's
no way that IPv4 would be able to handle this onslaught of new devices. NATing
would only work to some extent.

More IP addresses isn't the only reason to shift to IPv6,
though that was the original intention. Besides this reason, even the older IPv4
has some other limitations that IPv6 promises to overcome. These can be best
understood by looking at the benefits of IPv6. One is that the new protocol is
supposed to have better routing techniques. Unlike IPv4 implementations, in
which the routers maintain huge routing tables, IPv6 would be able to manage
with smaller tables. That's because a lot of information about the source and
destination is built into the IPv6 header itself. This will allow IPv6 packets
to reach their destinations in fewer hops.
Another limitation that IPv6 overcomes is getting an IP address from a
DHCP server. In IPv4, if a machine is configured to obtain an IP from a DHCP
server, it won't be able to get an IP address if the DHCP server isn't
available. IPv6 on the other hand, is supposed to be smart enough to figure out
an IP address from a routing table or from IP addresses of nearby clients.
Likewise, IPv6 is supposed to have better support for security, with integrated
IPSec support. Even if we look at the addressing scheme, we'll find many
benefits. Since there's such a huge number of IP addresses available, a
company won't really need to do NATing. Likewise, there can be more levels of
subnetting also possible.

Given all these benefits, there's some movement towards
implementing the protocol. The US federal agencies are supposed to shift to IPv6
by 2008. China, Korea and Japan have also been considering the shift to IPv6. In
fact, in July 2004, IPv6 records were visible for Japan and Korea's TLD (top
level domain) name servers became visible in the DNS root servers. The IPv6
records for France have also been added. Besides these, several key conferences
were hosted last year to create awareness about the protocol. Work is on at the
software front as well. Windows XP already has a trial deployment for it, while
some versions of Linux also support it. There's a company that's deploying a
DHCP server test suite for IPv6. The IPv6 forum has task forces from around 35
countries working on the protocol.

Despite all this action, IPv6 adoption is still a little
slow. Part of the reason is that it's not backward compatible with IPv4. An
IPv4 router won't support IPv6. It must have inherent support build in for
both protocols. Likewise, all applications and Operating Systems must add the
support for the new protocol. Just because this happens, it doesn't meant that
all companies and ISPs will immediately shift to the new protocol. It will take
time, as everybody would first have to understand the complexities and
challenges involved, do some pilot runs before doing the transition. Its
migration will be like any other technology. There will first be an intermediate
stage where, where both IPv4 and IPv6 will coexist. This will then slowly
transition to the new protocol. But the complete transition is not likely to
happen any time soon. Should you be worried about IPv6 now? Well, as there's
plenty of time for the transition to happen, you might like to consider doing
some dry runs of the same. It shouldn't happen that the world migrates to the
new protocol and enjoys its benefits, while you're left behind.

Anil Chopra, Associate Editor