ISPs had better be ready for World IPv6 Day on June 8, because they may hear from customers whose IPv6 connections don't work as expected.

That's the word from Martin Levy, director of IPv6 strategy at Hurricane Electric , a competitive service provider that has been touting its IPv6 roots for years now.

Levy is generally positive about the recent growth in IPv6 deployments, noting that IPv6 connections make up about 10 percent of Internet traffic now. But Levy is encouraging all ISPs to reach out to customers -- especially businesses -- as the IPv4 numerical addresses dwindle down to a precious few.

On June 8, major Internet sites such as Google, Facebook, Yahoo! and more will turn up IPv6 connectivity to allow IPv6-enabled endpoints to test their connectivity. Generally speaking, the Internet community thinks between 0.12 percent and 0.5 percent of connections will fail -- a small percentage overall but still a large number to companies that count on millions of transactions daily to fuel their Internet businesses.

When those customers don't succeed in connecting to their favorite websites, however, they aren't likely to call Google or Yahoo!, but they will call their ISP, and the volume of calls could disrupt business as usual if service providers aren't prepared.

"That's really who they should be calling," Levy says. "And the easiest way for those folks to fix the problem is to enable v6."

Levy says about 50 percent of service providers have IPv6 enabled, but those service providers tend to be well connected, that is, connected to eight or more other service providers. Networks in less densely populated areas with fewer connection options aren't as likely to have IPv6 networking available. (See Cable Show to Highlight IPv6 Transition , Verizon Expands IPv6 Support, AT&T Pushes IPv6 and Cable: We're Ready for IPv6.)

Levy says he deals daily with businesses that need IPv6 connections and are forced to connect to a network such as Hurricane Electric's through tunnels because of the lack of local IPv6 connection. Those tunnels are better than nothing, but not as robust as native IPv6 service. (See Hurricane Electric Offers IPv6 Aid to Enterprises.)

Smaller ISPs are the ones less likely to have IPv6 access available, even though they may have equipment that can handle the newer Internet addressing scheme. Wireless services also are less likely to be IPv6 on an end-to-end basis, using proxy servers and network address translation to handle conversions between IPv4 and IPv6, Levy says.

The big splash made earlier this year about IPv4 number exhaust at the global registry, as the final IPv4 address blocks were handed out to regional registries, has more ISPs and business customers taking action on v6 transition plans. At Interop last week, American Registry for Internet Numbers (ARIN) President John Curran said the IPv4 numbers left in North America should last "until the end of this year, maybe a little longer." (See Global IPv4 Counter Hits Zero.)

— Carol Wilson, Chief Editor, Events, Light Reading