A technology made famous by teenage digital music fans and since adopted by some of the world's biggest companies is making headway with the U.S. military.
Various forms of peer-to-peer technology, which allows computer users to bypass central servers and connect directly with one another, are being used to plan battlefield operations in Iraq and deliver humanitarian aid.
Microsoft Corp.'s NetMeeting software and programs from Groove Networks Inc. and Appian Corp. are part of the military's shift away from massive central computer servers toward more flexible models that let users work on joint projects and share information -- even when they are cut off from high-speed communication links.
Commanders in the Persian Gulf use collaboration software to chart progress, drawing on one another's maps during videoconferences several times a day, said J.P. Angelone, who heads the enterprise capabilities center at the Defense Information Systems Agency.
The data are kept on individuals' computers instead of a central server. When one person disconnects from the network, he can keep working on a personal version of the material. Logging in again automatically sends updates to the other participants.
"It's helpful because you reduce the physical distance to connect," Angelone said. "If you've got a command or a tactical unit in the area of responsibility, there's no sense coming all the way back to tap into a server."
The technology is largely off the shelf, relying on NetMeeting and audio and video add-ins for computers.
"Peer-to-peer" is a catchall phrase that describes a general approach; the actual systems vary widely in the way they're set up and in how decentralized they are.
The defunct song-swapping service Napster, for example, was a hybrid system that used central servers to direct its users to one another and then dropped out of the picture. A successor service, Gnutella, is more purely peer-to-peer, with no central index. Individuals use the Internet to find one another through small hubs, without a single point of failure that could crash the entire system if it shutdown.
The military is likewise employing a range of designs. The NetMeeting system used by commanders in the Iraq war falls somewhere in the middle.
The most decentralized so far may be in Army war games, which have thousands of participants connected to one another through phones and other hand-held devices.
"In the last couple of years, we've been able to go beyond relatively small peer-to-peer environments to massively large-scale ones," said Michael Macedonia, chief technology officer for the Army's Simulation, Training and Instrumentation command.
Groove's systems rely less on central machines than the NetMeeting system does. Nongovernmental aid workers from several countries are using Groove software to coordinate with one another and the military in southern Iraq.
"Usually, the people in the field are not connected to the Net," said Groove Senior Marketing Director Andrew Mahon. "But they can fill out electronic forms, answering questions about whether the water is polluted, whether there are any doctors in the area. When they get back to a communications vehicle, even with low bandwidth, they can send the information to [U.S. operations in] Kuwait and to others in the decision-making process."
A side benefit, Mahon said, is that no one controls the data: They are not all stored at the Pentagon or at an aid organization such as Save the Children. "Since no one owns the data, the dynamics of the space are fairly trust-engendering."
Groove is being tested by the Pentagon's Total Information Awareness program in hopes it will allow intelligence and law enforcement agencies to analyze data together.
Even the military's rank and file have access to some collaboration tools through such massive intranets as Army Knowledge Online, which has more than 1.2 million users. Officers and enlisted personnel can create virtual areas for information that are open to anyone, to just one unit or to those with appropriate security clearances.
Army Knowledge is highly centralized. The information is stored on servers, lessening the worry if troops' machines fall into enemy hands.
Another reason for not installing file-sharing software for most Army Knowledge subscribers is that "there's no way the Army could have afforded to upgrade 1.4 million desktops," said Mike Beckley, general partner of Appian, which is the lead contractor on the project.
But some are pressing for more independence from the main servers, especially the Navy. The Navy has ships with intermittent or narrow-bandwidth connections, so it plans to test a version that permits off-line collaboration similar to Groove's system, Beckley said.
Even in the Army, he added, "there are constant discussions about how performance would be improved if a unit could take Army Knowledge Online with them and synchronize back to central AKO later."
Coordinating the efforts toward decentralized computing is the Defense Information Systems Agency, which has installed basic collaboration tools at more than 63 sites worldwide. The Defense Collaboration Tool Suite already includes half a dozen commercial programs, and companies backing 17 more have asked to be considered, said the agency's Angelone.
"We want to help everyone inter-operate and be able to share information across the networks so they can collaborate with other commands with the tools of their choice," he said.
Angelone and others said peer-to-peer's progress toward the battlefield would continue because such systems are more resistant to attack and can be faster and easier to use than traditional, server-based setups.
"There are prototypes in development right now," said Stanley Manoski, a military technology advisor at Mitre Corp. "There are issues of security that still have to be dealt with, but within five years, I would think you would see systems that have more peer-to-peer ideas embedded in them."