IPv4 to IPv6: Not a simple migration

When the Internet Engineering Task Force finalized the IPv6 standard, experts thought the transition from IPv4 would be relatively smooth — similar to an operating system upgrade — but that's not the way it turned out.

"The further you get into the protocol the more you realize it's not a simple migration from one to the other. It's a completely new protocol," said Bruce Fleming, divisional technology officer for Verizon Federal Network Systems. "In the literature, they say it's an easy migration, but don't believe it."

Those organizations that make the transition will at some point have to deal with one or more of the following scenarios:

Dual stacks. Both IPv4 and IPv6 are supported on the same network, allowing an end user to receive IP traffic originating on either an IPv4 or IPv6 network. If the configuration is done correctly, the end user won't know the difference. Equipment vendors are now starting to support dual stacks. Siemens Subscriber Networks recently introduced dual-stack functionality for its tango Access broadband client for Microsoft Corp. Windows, and router vendors such as Cisco Systems Inc. have included IPv6 support in their systems for some time.

Tunneling. This function allows IPv6 packets to run over an IPv4 network by encapsulating IPv6 packets inside IPv4 packets or Multiprotocol Label Switching frames.

Translation. In this approach, traffic that originates under one protocol is converted into the other. It is used in situations in which IPv4 traffic must be converted to run on newer devices or when an organization has moved to IPv6 but still has IPv4 systems to support.

Whatever scenario is used, the transition must be transparent to end users, said Charles Lynch, chief of the IPv6 Transition Office in the Defense Information Systems Agency.