The depletion of the IPv4 allocation pool has been a concern since the late 1980’s, when the internet really started to see enormous growth. Since then there have been many techniques developed to address the IPv4 scalability issues (limited to 4.3 billion addresses) such as CIDR, NAT and finally the introduction of IPv6 in 1998.
IPv6 is the only workable solution to IPv4 depletion as it can provide 340 undecillion (3.4×1038) addresses. This therefore eliminates the need for NAT in the future internet. To put the numbers in perspective, if the current pool of IPv4’s 4.3 billion addresses were the size of a golf ball, the new IPv6’s 340 undecillion address space would be about the size of the sun.
IPv4 to IPv6 – The network problem
IPv4 and IPv6 are completely separate Network layer protocols that cannot interact directly. As the internet community rolls out IPv6, what is actually happening is the build out of a second, logical IPv6 internet, which runs in parallel and over the same physical Layer1 &2 infrastructure as the current IPv4 internet, with the eventual goal of phasing out the IPv4 Internet.
Since there is no set time limit when everything must be IPv6 network providers need to design and implement mechanisms that allow networks to work on IPv4 and IPv6 at the same time, and also, in preparation for the eventual date when IPv4 address space is completely exhausted, have a solution where they can deploy IPv6 only sites that can still communicate with the IPv4 Internet.
IPv4 to IPv6 – the solutions
Dual stack means that all devices are able to run both IPv4 and IPv6 in parallel. This is the solution that should be implemented now as it offers flexibility and coexistence, allowing users to reach both IPv4 and IPv6 simultaneously.
Dual stack does not require any tunnelling over networks as IPv4 and IPv6 work independently of each other. This allows for a granular migration of services from IPv4 to IPv6 over time.
Dual Stack Lite is a solution which is primarily adopted for broadband solutions. Its design does not require any registered IPv4 address space to be assigned to a Customer site. In this design only IPv4 private addresses for the LAN clients are used and IPv4 in encapsulated in IPv6 over the WAN.
The network provider implements a Carrier Grade NAT (CGN) device within its network infrastructure and the Dual Stack Lite CPE uses its unique IPv6 connection to deliver packets to the CGN which has a pool of IPv4 addresses.