The Domain Name System is coming apart at the seams. DNS, the protocol that maps IP addresses like 63.198.89.2 to domain names like www.dentistdirectory.com, is showing its age after almost 20 years. It has proved unable to adapt to dynamic Internet addresses, to the number of new services being offered, and particularly to the needs of end users, who increasingly use their PCs to serve files, host software, and even search for extraterrestrial intelligence. As these PCs become a vital part of the Internet infrastructure, they need real addresses just as surely as Yahoo! does. This is something the DNS system can't offer them, but the competitors to DNS can.

The original DNS system was invented back in the early 1980s for a distinctly machine-centric world. Internet-connected computers were rare, occupying a few well-understood niches in academic and government labs. This was a world of permanence: Any given computer would always have one and only one IP address, and any given IP address would have one and only one domain name. Neat and tidy and static.

Then along came 1994, the Year of the Web, when the demand for connecting PCs directly to the Internet grew so quickly that the IP namespace—the total number of addresses—was too small to meet the demand. In response, Internet service providers began doling out temporary IP addresses as individual PCs logged on to the Net. This wasn't a problem in the mid-1990s—clunky dial-up connections discouraged most people from logging on very often, so no one thought seriously about giving PCs discrete domain names.

Napster does it

Over the last five years, though, better hardware and decent connectivity via LAN, DSL, and cable have made it reasonable to be logged in all the time. But the DNS system got no better at all—anyone with a PC remained a second-class citizen with no address. It was Napster, ICQ, and their cousins, not the managers of the DNS system, who stepped into this breech.

These companies, realizing that interesting services could run on PCs if they had real addresses, simply ignored DNS and replaced the machine-centric model with a protocol-centric one. Protocol-centric addressing creates a parallel namespace for each piece of software, and the mapping of ICQ or Napster usernames to temporary IP addresses is handled by privately owned servers dedicated to each protocol instead of the Net's DNS servers.

In Napster's case, protocol-centric addressing merely turns Napster into a customized FTP for music files. The real action is in software like ICQ, which not only uses protocol-centric addressing schemes, but also allows the address to point to a person, not a machine. When I log into ICQ, I'm me, no matter what machine I'm at, and no matter what IP address is assigned to that machine. This completely decouples what humans care about (Can I find my friends and talk with them online?) from how the machines go about it (Route message A to IP address X).

This scenario is analogous to the change in telephony brought about by mobile phones. In the same way a phone number is no longer tied to a particular location but is now mapped to the physical location of the phone's owner, an ICQ address is mapped to me, not to a machine, no matter where I am.

This does not mean that the DNS system is going away, any more than land lines went away with the invention of mobile telephony. It does mean that DNS is no longer the only game in town. The rush is now on with instant messaging protocols, single sign-on and wallet applications, and the explosion in peer-to-peer businesses to create and manage protocol-centric addresses, because these are essentially privately owned, centrally managed, instantly updated alternatives to DNS.

Address books on steroids

However, this change is not entirely to the good. While ICQ and Napster came to their addressing schemes honestly, any number of people have noticed how valuable it is to own a namespace. So I'm seeing plenty of business plans that are just me-too copies of Napster or ICQ that could make an already growing list of kinds of addresses—phone, fax, email, URL, ICQ—explode into meaninglessness.

This could also lead to the rise of "meta address" servers, which offer to manage a user's addresses for all of these competing protocols, and even to translate from one kind of address to another. (These meta address servers will, of course, need their own addresses.)

It's not clear what is going to happen to Internet addressing, but it's clear that it's going to get a lot more complicated before it gets simpler. Fortunately, both the underlying IP addressing system and the design of URLs can handle this explosion of new protocols and addresses. But that familiar DNS bit in the middle (which really put the dot in dot-com) will never recover the central position it has occupied in the last two decades—and that means a critical piece of Internet infrastructure is now up for grabs.

(Thanks to Dan Gillmor of the San Jose Mercury News for pointing out to me the important relationship between peer-to-peer networking and DNS.)