IPv4 to IPv6 switch: When protocols collide

Shifting from IPv4 to IPv6 will take years and could be a bumpy ride. But few organisations will find the process as complicated as cloud computing providers, says Lori MacVittie.

Not since the first packets were tossed around the internet has it faced so much potential change, with implications for its health and well-being and, peripherally, cloud computing.

The recent World IPv6 Day gave a host of vendors, providers and interested parties the chance to engage in a full-scale IPv6 interoperability test live on the internet. Yet for many of the participants it wasn't just a test of IPv6 compatibility but an examination of what is considered one of the most promising migration strategies: dual-stack support.

As its name suggests, the dual-stack option involves running IPv4 and IPv6 networking stacks on the same system as a means to communicate with other nodes regardless of which version might be used.

Advantages of the dual-stack option

It's considered the best of the options available — when compared with tunnels and translators — because it's the simplest of the options to implement and provides the widest coverage of endpoint combinations.

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It's a strategy that allows for the reality that it's going to take a long time to migrate the entire world — every single device out there — from what has been the only standard the internet has really known to its successor, IPv6.

Given the reliance business, government and individuals have on the internet, there is no feasible way to accomplish a single, mass migration from IPv4 to IPv6. The process will be slow and take years. In the meantime, the onus is on those with a public-facing presence to somehow support both protocols.

Dual stacking meets that need well, because most infrastructure is already dual stacked. But running both stacks is not the same as using it to integrate and interconnect the myriad services — networking and application oriented — necessary to enable even the simplest of tasks to be completed.

DNS complexities

Consider the process of simply getting to a website, which is more complex than it sounds. DNS must be queried, packets routed, TCP sessions initiated, data exchanged. And that's only the tip of the iceberg.

Given the reliance business, government and individuals have on the internet, there is no feasible way to accomplish a single, mass migration from IPv4 to IPv6.

Inside the datacentre where that site resides is a multitude of components — hardware and software — that must interact to answer a query as simple as an ICMP echo request.

Being dual stacked does not necessarily address the need for services to support IPv6. Imagine an IPv4 endpoint requesting the IP address for a site. DNS must respond, but with what? Obviously an IPv4 address and not an IPv6 address.

Consider the reverse, as well. How does DNS know which IP version of the address to respond with? As we shift from one version to the next, we will be faced with...