Try to find an enterprise that's running IPv6 in production mode, and you'll likely come up empty handed. That's because few U.S. organizations are deploying or even testing the long-anticipated upgrade to the Internet's main protocol.

The exception to the rule is the U.S. federal government, which is required by the Office of Management and Budget to support IPv6 in its core networks by 2008. IPv6 offers an order of magnitude more address space than the current IPv4 protocol, along with built-in security, administration and quality of service features that have been added to IPv4 over the years.

I recently interviewed the officials at the Social Security Administration who are responsible for IPv6 deployment. Here's what they had to say about their hands-on experience with IPv6.

Migrating to IPv6 is a major undertaking for an agency as large as SSA, which has more than 120,000 users on its network. The agency's network, SSANet, links its headquarters in the Baltimore area with 1,500 locations nationwide.

SSANet is an all-IP network that was recently upgraded to support Multi Protocol Label Switching (MPLS) technology. It is a converged network that supports voice, data and video. SSAnet uses two carriers for redundancy: Verizon and AT&T.

At the core of SSANet are SSA's main data center, a new backup data center and six regional operational control centers. The links between these sites will support IPv6 in a dual-stack mode - running IPv6 and IPv4 concurrently - by June 2008.

SSA has been working with IPv6 since 2001, when it first identified IPv6 as an emerging technology. SSA was one of the first organizations in the United States to acquire IPv6 address space.

One advantage for SSA in migrating to IPv6 is the fact that it manages and controls its network infrastructure and IP addressing centrally.

"The key here is how you manage your IPv4 address space," says Rich Terzigni, senior network advisor in SSA's Office of Telecommunications and Systems Operations. "How you manage that will prime you for IPv6."

SSA has conducted extensive IPv6 testing. The agency participates in Moonv6, the IPv6 testbed run by the North American IPv6 Task Force http://www.moonv6.org. SSA also is testing IPv6 in its own independent test lab, which analyzes all new technologies before installation on the production SSANet.