Network operators must run both protocols because IPv6 is not backwards compatible, a reality that many CIOs and CTOs just don't believe possible. Indeed, the Internet engineering community has said that its biggest mistake in the design of IPv6 is that it is not backwards compatible with IPv4.
"Lots of people think that IPv4 and IPv6 are compatible and that not a lot of action is going to be required to interoperate between IPv4 and IPv6 hosts," McPherson says. "If they don't have dual stack, then they will need some translation device."
IPv6 was once touted as the end of network address translation (NAT) devices, which Internet purists hate because they interrupt IP communications midstream. But network operators have delayed upgrading to IPv6 for so long that now they will need to rely on carrier-grade NATs and other IPv6-to-IPv4 translators to accommodate a rise in IPv6 network traffic that is expected to start within the next 12 months.
"Most of the transition technologies are either NATs themselves or are designed to work through NATs," Liu says. "Teredo [an IPv6-over-IPv4 tunneling technology] is designed to work through NATs. Nat64 [an IPv6-to-IPv4 translation scheme] is a NAT technology. I don't think NATs are going away anytime soon."
Liu says he hopes that by 2016 most of the Internet's backbone will be upgraded to IPv6 and that there will be just pockets of IPv4-only connectivity.
"For the next five years, things are going to be much more complex because we will have two protocols running side by side," Liu says. "We're going to have all of those crazy transition technologies. Not just one, but many...It's a rose-colored view of the world to believe that IPv6 is suddenly going to bring us to this network nirvana of end-to-end."
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This story, "The 6 biggest misconceptions about IPv6" was originally published by Network World.