IP: Gnutella and Freenet Represent True Technological Innovation

[Dave Farber <farber@cis.upenn.edu>]

>Date: Sun, 14 May 2000 09:12:39 -0700
>From: "Tim O'Reilly" <tim@oreilly.com>
>To: farber@central.cis.upenn.edu
>
>
>A must-read for people who've heard about these technologies and want a
>clear exposition of how they work, not just fearmongering about them.
>Whether you love or fear Napster and its even more revolutionary cousins
>gnutella and freenet, this is an article you ought to read.
>
>http://www.oreillynet.com/pub/a/network/2000/05/12/magazine/gnutella.html
>
>"The computer technologies that have incurred the most condemnation
>recently --
>Napster, Gnutella, and Freenet -- are also the most interesting from a
>technological
>standpoint. I'm not saying this to be perverse. I have examined these
>systems'
>architecture and protocols, and I find them to be fascinating. Freenet
>emerged from
>a bona fide, academically solid research project, and all three sites
>are worth serious
>attention from anyone interested in the future of the Internet."
>
>--
>Tim O'Reilly @ O'Reilly & Associates, Inc.
>101 Morris Street, Sebastopol, CA 95472
>+1 707-829-0515, FAX +1 707-829-0104
>tim@oreilly.com, http://www.oreilly.com<x-html>
>
>
>
><http://www.oreillynet.com>
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>
>
>by Andy Oram
>05/12/2000
>
>Related Articles:
>
>Napster and MP3: La Revolucion or La Larceny?
>
>Music Industry Turns Heat on Net Music Pirates
>
>Why the RIAA is Fighting a Losing Battle
>
>Napster: Popular Program Raises Devilish Issues
>
><http://dave.oreillynet.com/stories/storyReader$13>Why the RIAA Still 
>Stands a Chance
>
>The computer technologies that have incurred the most condemnation 
>recently -- <http://www.napster.com/>Napster, 
><http://gnutella.wego.com/>Gnutella, and 
><http://freenet.sourceforge.net/>Freenet -- are also the most interesting 
>from a technological standpoint. I'm not saying this to be perverse. I 
>have examined these systems' architecture and protocols, and I find them 
>to be fascinating. Freenet emerged from a bona fide, academically solid 
>research project, and all three sites are worth serious attention from 
>anyone interested in the future of the Internet.
>
>In writing this essay, I want to take the hype and hysteria out of current 
>reports about Gnutella and Freenet so the Internet community can evaluate 
>them on their merits. This is a largely technical article; I address the 
>policy debates directly in a companion article, 
><http://www.webreview.com/pub/2000/05/12/platformindependent/index.html>The 
 > Value of Gnutella and Freenet. I will not cover Napster here because its 
>operation has received more press. It's covered in "Napster: Popular 
>Program Raises Devilish Issues" by Erik Nilsson, and frankly, it is less 
>interesting and far-reaching technically than the other two systems.
>
>In essence, Gnutella and Freenet represent a new step in distributed 
>information systems. Each is a system for searching for information; each 
>returns information without telling you where it came from. They are 
>innovative in the areas of distributed information storage, information 
>retrieval, and network architecture. But they differ significantly in both 
>goals and implementation, so I'll examine them separately from this point on.
>
>
>Gnutella basics
>
>
>
>Each piece of Gnutella software is both a server and a client in one, 
>because it supports bidirectional information transfer. The Gnutella 
>developers call the software a "servent," but since that term looks odd 
>I'll stick to "client." You can be a fully functional Gnutella site by 
>installing any of several available clients; lots of different operating 
>systems are supported. Next you have to find a few sites that are willing 
>to communicate with you: some may be friends, while others may be 
>advertised Gnutella sites. People with large computers and high bandwidth 
>will encourage many others to connect to them.
>
>Evil or Just Controversial?:
>
>Open Source software such as Gnutella and Freeware are spreading as 
>quickly as a virus. But are they really so unhealthy? Andy Oram points out 
>the advantages--and disadvantages--of controversial technologies in this 
>week's edition of 
><http://www.webreview.com/pub/2000/05/12/platform/index.html>Platform 
>Independent on Web Review.
>
>You will communicate directly only with the handful of sites you've agreed 
>to contact. Any material of interest to other sites will pass along from 
>one site to another in store-and-forward fashion. Does this sound 
>familiar, all you grizzled, old UUCP and Fidonet users out there? The 
>architecture is essentially the same as those unruly, interconnected 
>systems that succeeded in passing Net News and e-mail around the world for 
>decades before the Internet became popular.
>
>But there are some important differences. Because Gnutella runs over the 
>Internet, you can connect directly with someone who's geographically far 
>away just as easily as with your neighbor. This introduces robustness and 
>makes the system virtually failsafe, as we'll see in a minute.
>
>Second, the protocol for obtaining information over Gnutella is a kind of 
>call-and-response that's more complex than simply pushing news or e-mail. 
>Figure 1 shows the operation of the protocol. Suppose site A asks site B 
>for data matching "MP3." After passing back anything that might be of 
>interest, site B passes the request on to its colleague at site C -- but 
>unlike mail or news, site B keeps a record that site A has made the 
>request. If site C has something matching the request, it gives the 
>information to site B, which remembers that it is meant for site A and 
>passes it through to that site.
>
>Figure 1. How Gnutella retrieves information
>
>I am tempted to rush on and describe the great significance of this simple 
>system, but I'll pause to answer a few questions for those who are curious.
>    * How are requests kept separate? Each request has a unique number, 
> generated from random numbers or semi-randomly from something unique to 
> the originating site like an Ethernet MAC address. If a request goes 
> through site C on to site D and then to site B, site B can recognize from 
> the identifier that it's been seen already and quietly drop the repeat 
> request. On the other hand, different sites can request the same material 
> and have their requests satisfied because each has a unique identifier. 
> Each site lets requests time out, simply by placing them on a queue of a 
> predetermined size and letting old requests drop off the bottom as new 
> ones are added.
>    * What form does the returned data take? It could be an entire file of 
> music or other requested material, but Gnutella is not limited to 
> shipping around files. The return could just as well be a URL, or 
> anything else that could be of value. Thus, people are likely to use 
> Gnutella for sophisticated searches, ending up with a URL just as they 
> would with a traditional search engine. (More on this exciting 
> possibility later.)
>    * What protocol is used? Gnutella runs over HTTP (a sign of Gnutella's 
> simplicity). A major advantage of using HTTP is that two sites can 
> communicate even if one is behind a typical organization's firewall, 
> assuming that this firewall allows traffic out to standard Web servers on 
> port 80. There is a slight difficulty if a client behind a firewall is 
> asked to serve up a file, but it can get by the firewall by issuing an 
> output command called GIV to port 80 on its correspondent. The only 
> show-stopper comes when a firewall screens out all Web traffic, or when 
> both correspondents are behind typical firewalls.
>    * How does the system stop searching? Like IP packets, each Gnutella 
> request has a time-to-live, which is normally decremented by each site 
> until it reaches zero. A site can also drastically reduce a time-to-live 
> that it decides is ridiculously high. As we will see in a moment, the 
> time-to-live limits the reach of each site, but that can be a benefit as 
> well as a limitation.
>    * How is a search string like "MP3" interpreted? That is the $64,000 
> question, and leads us to Gnutella's greatest contribution.
>Pages: 1, 2, 3, 4
>
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