The P2P myth

By John Borland
Staff Writer, CNET News.com
October 26, 2000, 4:00 a.m. PT

In the first hours after a judge ordered Napster to pull the plug on much of its popular service this summer, pure peer-to-peer networks faced trial by fire.

Fearful of losing access to the huge amounts of free music on Napster, people flooded to Gnutella, the decentralizedfile-swapping program widely seen as heir to Napster's crown.As a result, much of the Gnutella network slowed almost to a halt for twoexcruciating days.

For many of the technology's advocates, the clogged pipes served as somethingof a wake-up call. Gnutella is only one early version of a purepeer-to-peer network, but the incident spotlighted serious potentialproblems in replacing industrial-strength routers and servers with ordinaryhome computers: The network was only as strong--and as fast--as its weakestlinks.

In the new world of peer-to-peer, where individual machines stand in forthe Web's massive arrays of servers, that means a host of home computerswith dial-up connections risk becoming speed bumps.

"It turns out that dial-up modems simply can't handle all the traffic,"said Kelly Truelove, chief executive of Clip2, a consulting and software companythat works with Gnutella developers. "What that means is that individualhosts in the network become bottlenecks."

That lesson will resonate for years to come, as developers eager to bringindividual computers into a central role through P2P networks struggle withthe limitations of those machines. If they can't overcome such limitations,then much of the revolutionary rhetoric surrounding the model may need tobe tempered.

Developers, however, are optimistic, noting that P2P applications andnetworks are still in their commercial infancy.

"I don't think as a concept peer-to-peer applications are inherentlyflawed," said Kevin Smilak, chief technology officer of Web file-swappingcompany Scour. "I think current implementationsare flawed."

A fallible freedom?
In the increasingly corporate arena of the Web, bandwidth and speed areparamount. Telecommunications companies and Web hosting centers arespending billions of dollars to create fast, redundant connections and hugebanks of servers that can spit out gigabytes of data and serve hundreds ofthousands of surfers at a time.

But all of this winds up being expensive. The Web is seen as a distributionrevolution where digital transmission can eliminate the high costs ofpaper, trucks and gasoline. However, bandwidth costs and fees forNet-speeding services such as Akamai Technologies have taken their place,particularly for companies distributing big audio or video files.

Peer-to-peer networks can help curb these costs. A given file could behosted by 10,000 individual computers, eliminating the need to concentratebandwidth spending on a central location. Even consumers can play roles ashubs of distribution, such as they do on a widespread--even if potentially illegal--basis withMP3 files and Napster.

But the way these individual computers are connected can lead to networkheadaches, as Gnutella's early troubles showed. Avoiding the Web'scentralization means leaving behind much of the work that has gone intomaking it commercially stable.

The most famous P2P systems, such as Napster and Scour, aren't actually pureexamples of the model. Searches of those networks still run through acentral server. As long as those companies build enough capacity to handlethe traffic, the networks will run fairly well.

Gnutella is different. A Gnutella search is broadcast across a network thatchanges from moment to moment, going from one individual computer to fourothers, from those to sixteen others and so on. Search results are returnedalong the same pathway they originally traveled.

Thus, if many people are connected at the same time, many searches arelikely rippling through the network at the same time. And if any singlecomputer gets choked--as dial-up connections easily can do when they start handling about 10 searches per second--traffic upstream and downstream can tailspin into a sputtering mess.

This will be a problem in any peer-to-peer system that relies on individual computers to route searches and requests, or to host the most popular content.

"You can't ask end users to upgrade machines or memory just because thecontent they're serving becomes popular," said David Weekly, one of theindependent computer consultants who helped release ="http: opennap.sourceforge.net="" "="">Napster's technology into the open-source world.

Sidestepping the roadblocks
Several ways of getting around dial-up sinkholes have been proposed or arealready filtering into the marketplace.

Some developers say Gnutella itself can be salvaged by creating what somehave dubbed "super peers," which serve as stand-ins for dial-up modem usersbut have fast connections themselves.

Under this model, several dial-up computers would connect to anothermachine, which would read which files they were sharing and pass thisinformation to the rest of the network. Searches rippling through the network would be filtered only through the fast super-peer and would skip slow machines.

Clip2 has released one free product like this already, dubbed the Gnutella"Reflector." Otherdevelopers are discussing models that can "add intelligence" to the wayGnutella and other P2P systems route traffic and use available bandwidth.

"Bandwidth consumption has always been a problem, but with improvements inthe software--and the Reflector--it's significantly improving," said GeneKan, one of the programmers who has been a key part of Gnutella'spropagation. "It's like we're at the top of a cliff, and just putting alittle more energy into the work will put us over."

Then there's Freenet, one ofthe most high-profile still-in-development systems ever to make headlines.

Freenet is built on a different and more complicated model thanGnutella, Napster or any of their clones. Other peer-to-peer networks focuson connecting the computer that hosts content with the one asking for thefile. Freenet has programming built in that makes sure that this contentwinds up being as close as possible to the people who routinely ask for it.

Moreover, its technology has enough information built in that requests canbe routed almost directly to the place where the content is likely to bewithout having to search every connected computer.

Each of these features, at least in theory, radically reduces the amount oftraffic flowing through the network. Because it is still in the designstage, however, Freenet has yet to face the same large-scale tests that have exposed Gnutella's flaws.

The hurdles faced by peer-to-peer networks partly stem from the model'simmaturity. Until recently, the model was ignored by most reputablecomputer scientists and was the province of only a scattered group ofindependent programmers.

"We're reaching the limitations of the individual developer to develop,"Kan said. "There are limitations when people are doing this in their freetime and without a team. It will take companies and people working fulltime to push the envelope any further." 

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