ipv6 testingThis past Thursday September 24 will be remembered as the day that the North American registry ran out of IPv4 addresses. It’s not a big deal yet because Internet service providers, large enterprises and other parties still have plentiful stockpiles of IPv4 addresses. More importantly, the Internet community has been anticipating this day for years and a considerable amount of work has gone into preparing for this eventuality.

Those preparations are based largely on implementing what’s known as dual stack technology and should keep everything running smoothly – at least for a while. As their own IPv4 stockpiles run out, however, service providers may have to take additional steps to bridge the traditional IPv4 world with the new world of IPv6 – even if they have already deployed dual stack capability.

IPv4 to IPv6 Transition
Understanding what’s in store starts with some IPv4 and IPv6 basics.

As Comcast Fellow and Chief IPv6 Architect John Brzozowski explained in a blog post published Thursday, the IPv4 protocol – created in 1981 — can support fewer than 4.3 billion IPv4 addresses.

“[W]ith more than 2 billion connected people worldwide, and countless Web sites, computers and connected devices all needing IP numbers, it’s easy to see how we ran out,” he said. The IPv6 protocol, designed to replace IPv4, can support 340 undecillion (or 340 trillion trillion trillion) IP addresses, Brzozowski noted, adding that IPv6 also is a more secure standard. 

The downside is that IPv4-only endpoints can’t communicate directly with IPv6-only endpoints.

For North American service providers, preparations for the transition to IPv6 primarily have involved getting networks to support dual stack capability – an approach that assigns both an IPv4 and an IPv6 address to Internet endpoints. That way the user can reach either type of endpoint.

Comcast has been one of the most aggressive service providers in deploying dual stack, announcing last year that it was the first major U.S. ISP to deploy dual stack throughout 100% of its network

Eventually, though, service providers are going to use up their own IPv4 stockpiles, which means that dual stack won’t be an interoperability solution for new end users added to the network. If there are still some IPv4-only endpoints around at that time, the providers will need to deploy carrier network address translation (NAT) or another solution that lets IPv6-only endpoints communicate with IPv4-only endpoints. 

A Comcast spokesman used the term “transition technologies” as a catch-all term for technologies such as carrier-grade NAT that are designed to support legacy IPv4-only communications on the Internet as IPv4 resources become scarce. 

“In the future, as IPv4 resources diminish, everyone across the Internet ecosystem may need to consider transition technologies to complete the adoption of IPv6,” the spokesman said.

Of course the more extensively IPv6 has been deployed, the less the need for transition technologies will be.

“We believe the best way to limit the impact of such transition technologies and ensure the best experience for our customers is to aggressively adopt and promote IPv6, which is what we have done for more than a decade and will continue to do into the future,“ the spokesman said.

The spokesman said Comcast does not have a timeframe in mind for deploying transition technologies but is keeping a close eye on the situation.

A Global Perspective
North American service providers are not the only ones coping with IPv4 address exhaust. Of the five global Internet address registries only the one in Africa has IPv4 addresses remaining, according to Comcast.

Data from Akamai’s latest “State of the Internet” report suggests North American service providers have been most proactive in preparing for IPv6, however. One of Akamai’s measurements looks at the percentage of total content requests made to Akamai over IPv6 – and North American service providers held five of the six top spots in the second quarter of 2015.

Source: Akamai

Akamai estimates that the number of IPv4 addresses in use worldwide declined by 8.6 million between the first and second quarter of 2015.

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