The US Department of Defense (DOD) is to set to explain why IPv6 (Internet Protocol version 6) is critical for the nation's defence. The company has called a web conference in which it will present its plans for a two-week test programme, called Moon, that will examine interoperability of IPv6 equipment, software and services.

One of the major factors driving the move from the current version of IP version 4, to IPv6 is a perceived scarcity of IP addresses for new devices such as Internet-enabled mobile phones. IPv4 addresses are 32 bits long, enough for around 4 billion unique addresses, although inefficiencies in the division and allocation of the address space means that many of these are not available for use. IPv6 extends the address length to 128 bits, or around 340 billion billion billion billion [BBBB] unique addresses.

While governments and network operators in Europe and Asia have been conducting large-scale tests of IPv6 for the last three years, the US response to IPv6 has been "lackluster," according to the Web site of Moon's organisers. And the country is still playing catch-up: the tests the DOD will present originally were due to begin on 3 October and finish Friday, but have not yet begun, according to information provided by the organisers.

Participants in the Moon tests include the DOD, the Interoperability Laboratory of the University of New Hampshire, the North American IPv6 Task Force, networking software and equipment vendors including IBM, Microsoft, Hewlett-Packard, Cisco Systems, Fujitsu, Sun Microsystems and Nokia, and the Japanese network operator Nippon Telegraph and Telephone (NTT).