Few grass-roots technical innovations have caught on so quickly or mushroomed to such an incredible magnitude as the peer-to-peer (P2P) music-sharing engine, Napster. And few techno-creations of any kind, at any time, have created such fear and loathing in the communications and entertainment businesses.

Yet cellphone maker Nokia is proposing to build a new iteration of that ultimate disruptive technology, a P2P file-sharing network. And it's dreaming up some pretty cool technical slight of hand to pull it off.

Here's the story:

The mobile phone giant is working with Budapest University of Technology and Economics in Hungary to bring P2P file swapping to the wireless community. Still in testing, the solution already works with pictures and text—with other forms of mobile content, including compressed audio files like MP3s, coming soon.

Similar to traditional desktop file sharing solutions like Kazaa, Gnutella, WinMX and SoulSeek, Nokia's P2P implementation uses the Internet to connect clients. But instead of PCs, the clients in question will be mobile handsets.

Unlike Napster, which relied on a central server to store content and connect clients, today's file swapping services implement true peer-to-peer networking, which bypasses a central server completely and lets individuals connect to each other directly. That's one reason why these other services have, so far, avoided Napster's fate. Although Nokia's proposed P2P mobile phone solution circumvents the potential pitfall of a centralized server as well, it is, at the same time, not P2P in the conventional sense. Instead of connecting all clients to each other individually, Nokia plans to implement what it calls parallel index clustering.

Mechanics
Mobile phone clients are aggregated into a group called a cluster. Each member of the cluster is capable of viewing a complete index of what all that cluster's members are sharing. All the clusters on the network then run in parallel as their own little P2P file swapping worlds.

The goal of parallel index clustering is to make better use of the limited bandwidth and speeds of mobile phone networks—which, of course, is not a problem with a broadband connection to a PC. Although it does this by limiting a user's search to his or her cluster, it could conceivably allow users to search from cluster to cluster by reducing each cluster to a single peer.

With a cluster plausibly encompassing hundreds or thousands of clients, this would, in theory, greatly reduce the number of peers you would need to search when looking for a file, while at the same time maximizing the number of files you search.

Roadblocks
It appears that the technical challenges of P2P networking for mobile handsets are surmountable, with storage seemingly a major bump in the road. (A new Samsung phone, SPH-V5400—available only in South Korea for around a hefty $800—integrates a 1.5GB hard disk, huge for a mobile phone but minuscule by desktop file sharing standards.)

The legal hurdles, on the other hand, may not be.

That's because the music industry and others continue to fight P2P networks tooth and nail. These industries probably won't sit by idly while yet another potential threat to their intellectual property comes into being.

In addition, mobile operators are the key to success for any such system. Even through Nokia's position as the number one mobile phone vendor gives it a lot of influence, it still relies on carrier support to get products and services into consumers' hands.

That could be a problem, with P2P file sharing, as operators favor centrally managed services for maximum control. They may also be leery about stepping into the legal storm surrounding P2P file networks.