Ever since KaZaA founder Niklas Zennstrom let it slip in a Boardwatch interview that he was planning to launch a company offering voice services using peer-to-peer (P2P) protocols, Light Reading and Boardwatch have been puzzling over what he meant.

As Zennstrom himself has clammed up, speculation is in order. And our best guess is that he might be onto something REALLY BIG. Think bigger than Google. Think of something equivalent to the Internet's Domain Name System (DNS) that would act as a distributed, dynamic, global telephone directory, linking users with whatever IP address their appliance happened to be using at the moment.

This addresses one of the big obstacles in the development of voice over IP (VOIP), and it might also unlock other breakthroughs. For instance, it could speed up the convergence of fixed and mobile telephony -- reckoned by Niel Ransom, CTO of Alcatel SA (NYSE: ALA; Paris: CGEP:PA), to be the next big thing in telecom (look for the coming Light Reading interview).

It would be fairly straightforward to use P2P protocols to create such a distributed, global telephone directory, according to Geoff Bennett, director of Light Reading University, who happens to be moderating a Light Reading Webinar titled "Controlling P2P: Who's Stealing Your Bandwidth?" today, at 2:00 p.m. New York time. (Click here to register for the free, live broadcast.)

With P2P, a user could search a directory using a special browser and then click on the name he or she wanted to call. The client software would send the request to the equivalent of a KaZaA supernode that would search a giant routing table listing users and their current IP addresses, and send back the result to the client so the VOIP call could be set up.

This is pretty much how file sharing works, and file sharing clearly scales to the millions of users that might take advantage of such a system. Zennstrom estimates that 100 million people already use P2P protocols, and the KaZaA browser software has been downloaded a staggering 250 million times -- an order of magnitude more than anything else on CNET's download site.

There are good reasons to believe that a P2P-based phone directory of this sort might work better than the VOIP solutions being cooked up by the Internet Engineering Task Force (IETF).

The IETF has various projects in this area, but they're all based on the fundamental philosophy that existing technology -- namely DNS -- should be adapted to deal with new requirements, rather than inventing something new.

But the new requirements in this case include more than just the IETF's Telephone Number Mapping (enum) project.

The IETF has also got to come up with a way of making DNS more dynamic, so that when a user moves from one IP address to another, he or she isn't cut off from the world while the changes propagate through the DNS hierarchy. When Boardwatch changed IP address earlier this year, a lot of readers were cut off for two or three days. Imagine the same thing happening every time someone shifted from a fixed to a mobile appliance!

Then there's the issue of reliability. Concerns are often expressed about the security of DNS -- in particular, its vulnerability to denial-of-service (DOS) attacks. A P2P approach promises to be much more reliable, because it's so distributed and because the protocol has been designed to allow for parts of the network going AWOL unexpectedly.

"Historically, the issue with proprietary solutions has been lack of scaleability, and how robust they are in large networks," Bennett notes. "But P2P apps like KaZaA have shown they can scale and have amazing resilience because they're so distributed. How do you make a DOS attack on something that big?

"The P2P solution will obviously be proprietary, and it's always quicker to get a proprietary solution to market than to wait for consensus in a standards group -- especially about something as institutionalized as DNS."

For more on IETF side of the story, check out the following columns by Geoff Huston, a member of the Internet Architecture Board, the IETF steering body:

Light Reading is rather hoping that this speculation will encourage Zennstrom to spill the beans on what he's up to. Right now, we think we've only got half the story. The other half concerns SIP -- the Session Initiation Protocol -- seen by some as another catalyst for a VOIP explosion. In the Boardwatch interview Zennstrom slapped down the idea that his project had anything to do with SIP. Which leads us to ask: Why was he so adamant?

— Peter Heywood, Founding Editor, Light Reading