March 26 – 29 , 2006, Dagstuhl Seminar 06131

Peer-to-Peer-Systems and -Applications


Anthony D. Joseph (University of California – Berkeley, US)
Ralf Steinmetz (TU Darmstadt, DE)
Ion Stoica (University of California – Berkeley, US)
Klaus Wehrle (RWTH Aachen, DE)

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Under the term “Peer-to-Peer”, a very promising paradigm for communication in the Internet arises. Though it was originally used for pragmatic and not always legal file-sharing activities, the Peer-to-Peer technology offers interesting opportunities for highly distributed and scalable systems and applications.

According to recent reports from ISPs, a major amount of Internet traffic is governed by Peer-to-Peer applications. Due to the continuing growth and diversification of the Internet and its applications, it becomes exceedingly difficult to meet the resource demands by traditional Client-Server solutions. These centralized approaches can be hardly realized for, e.g., file sharing applications, distributed file systems, or grid computing environments.

Given this persistent and long-term development, there are three fundamental challenges for current and future Internet applications:

  • Scalability is of utmost importance in order to cope with user bases and resource consumption of applications (in terms of bandwidth, storage, processing, etc.) growing by several orders of magnitude.
  • Only through security and reliability it is possible to maintain the availability of centralized services in the face of distributed denial-of-service attacks. Data privacy and censorresistance are also of growing concern.
  • Flexibility and quality of service allow the rapid deployment of new technologies throughout the Internet, e.g. to realize long-promised multicast and host mobility features.

The Peer-to-Peer paradigm shows the potential to meet these challenges. Peer-to-Peer systems share distributed resources and address services based on content rather than location. Without the necessity for central entities, they organize themselves into cooperating infrastructures of symmetric peers. The two approaches of structured vs. unstructured P2P systems allow for different and sometimes complementary trade-offs and still bear a wide range of ongoing and future research in the P2P area.

The goal of the second Dagstuhl seminar on Peer-to-Peer-Systems and –Applications was to assemble researchers being highly active in the area of Peer-to-Peer mechanisms and networking

  • (1) to reflect on recent research activities,
  • (2) to identify future research issues, i.e. major challenges and
  • (3) to strengthen the Peer-to-Peer community in research


  • Networks


  • Peer-to-Peer
  • Self-organization
  • Massively distributed systems


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