Report from Internet2/SURA P2P conference

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Andy Oram
Feb. 05, 2002 05:21 AM

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Last week I visited a surprisingly chilly Phoenix, Arizona to deliver a keynote speech at the workshop Collaborative Computing in Higher Education: Peer-to-Peer and Beyond. I no longer think that P2P requires its own distinctive research, but I still find that people trying to meet the needs of P2P infrastructure and applications are doing some of the most interesting work in computing. Here are some key points I heard at the conference. A longer article with more general points will be posted later this week.

  • The value of a peer-to-peer mindset is shown in a modest project called Your Own Internet Distribution, presented by Bob Lindell. Its goal is to produce an efficient multicast system for networks that don't support IP multicast.

    According to Lindell, a typical way someone might add users to a multicast would be to build a mesh in which all users are fully connected—for instance, ten (4+3+2+1) connections for five users. Then the application would perform some sophisticated routing analysis and come up with a hierarchical tree that represents the best routes between all users. The problem is that the application would have to rebuild the mesh and the tree every time a user comes or goes, and that creates burdensome overhead in a real-life situation.

    A P2P mindset takes account of transient users and designs a solution that is less elegant in theory but more workable in practice. No mesh is created, but each user that connects is added to the best point in the tree. If one node becomes overwhelmed with traffic, it kicks one or more children off the tree and they rejoin it elsewhere.

  • Bill St. Arnaud, as well as other presenters, emphasized that there are plenty of legitimate applications, especially peer-to-peer applications, that require high bandwidth. So bandwidth problems won't go away, even if all the file-sharing sites are shut down.

    St. Arnaud, who helps Canadian universities develop fiber networks, is in a highly unusual position because his colleagues have plenty of bandwidth and are looking for applications to fill it. His presentation showed some promising educational projects.

  • Most university administrators, in contrast, really need to rein in file sharing. It's driving normal research- and class-oriented traffic off of their networks. The most promising technologies for "traffic shaping" don't involve blocking particular ports (because file sharing programs can work around that) or hard limits on usage (because a lot of network users have big bandwidth needs for good reasons related to university business). Instead, sophisticated traffic shaping watches each users' bandwidth use and gradually cuts down on the bandwidth allocated to them as usage increases.

  • Two projects illustrate the validity of a peer-to-peer approach in ways that are particularly easy to see:

    • Porivo, presented by CEO Gordon Kass, is a commercial venture about which I wrote a profile last year. Porivo installs its software on participating end-user sites to test the responsiveness of web sites under absolutely realistic conditions.

    • SHOCK, a research project presented by Eytan Adar, lets people find authorities on particular subjects while maintaining the privacy of both the authorities and the requesters. Each expert stores a profile on his or her personal computer and the profile is queried when anyone sends a request to the network for help.

    In addition, Raymond Leung described a video distribution system (an application pursued by lots of P2P researchers) that depends on storing chunks of videos on users's systems, and Werner Vogels presented a publish/subscribe system that pushes new articles of interest through a chain of users.

Andy Oram is an editor for O'Reilly Media, specializing in Linux and free software books, and a member of Computer Professionals for Social Responsibility. His web site is