The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.

Enabling Technologies for Decentralized Interpersonal Communication

Jani Hautakorpi

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Faculty of Information and Natural Sciences for public examination and debate in Auditorium T2 at the Aalto University School of Science and Technology (Espoo, Finland) on the 12th of November 2010 at 12 noon.

(ISBN 978-952-60-3449-2)
Dissertation is also available in print (ISBN 978-952-60-3448-5)


In the recent years the Internet users have witnessed the emergence of Peer-to-Peer (P2P) technologies and applications. One class of P2P applications is comprised of applications that are targeted for interpersonal communication. The communication applications that utilize P2P technologies are referred to as decentralized interpersonal communication applications. Such applications are decentralized in a sense that they do not require assistance from centralized servers for setting up multimedia sessions between users.

The invention of Distributed Hash Table (DHT) algorithms has been an important, but not an inclusive enabler for decentralized interpersonal communication. Even though the DHTs provide a basic foundation for decentralization, there are still a number of challenges without viable technological solutions. The main contribution of this thesis is to propose technological solutions to a subset of the existing challenges.

In addition, this thesis also presents the preliminary work for the technological solutions. There are two parts in the preliminary work. In the first part, a set of DHT algorithms are evaluated from the viewpoint of decentralized interpersonal communication, and the second part gives a coherent presentation of the challenges that a decentralized interpersonal communication application is going to encounter in mobile networks.

The technological solution proposals contain two architectures and two algorithms. The first architecture enables an interconnection between a decentralized and a centralized communication network, and the second architecture enables the decentralization of a set of legacy applications. The first algorithm is a load balancing algorithm that enables good scalability, and the second algorithm is a search algorithm that enables arbitrary searches. The algorithms can be used, for example, in DHT-based networks. Even though this thesis has focused on the decentralized interpersonal communication, some of the proposed technological solutions also have general applicability outside the scope of decentralized interpersonal communication.

This thesis consists of an overview and of the following 6 publications:

  1. Jani Hautakorpi and Gonzalo Camarillo. 2007. Evaluation of DHTs from the viewpoint of interpersonal communications. In: Timo Ojala and Mika Ylianttila (editors). Proceedings of the 6th International Conference on Mobile and Ubiquitous Multimedia (MUM 2007). Oulu, Finland. 12-14 December 2007. New York, NY, USA. ACM. Pages 74-83. ISBN 978-1-59593-916-6. Invited paper. © 2007 Association for Computing Machinery (ACM). By permission.
  2. Erkki Harjula, Jani Hautakorpi, Nicklas Beijar, and Mika Ylianttila. 2009. Peer-to-Peer SIP for mobile computing: Challenges and solutions. In: Boon-Chong Seet (editor). Mobile Peer-to-Peer Computing for Next Generation Distributed Environments: Advancing Conceptual and Algorithmic Applications. IGI Global. Chapter XV, pages 326-347. ISBN 978-1-60566-715-7. © 2009 IGI Global. By permission.
  3. Jani Hautakorpi, Arturo Salinas, Erkki Harjula, and Mika Ylianttila. 2008. Interconnecting P2PSIP and IMS. In: Khalid Al-Begain and Antonio Cuevas Casado (editors). Proceedings of the Second International Conference on Next Generation Mobile Applications, Services, and Technologies (NGMAST 2008). Cardiff, Wales, United Kingdom. 16-19 September 2008. IEEE. Pages 83-88. ISBN 978-0-7695-3333-9. © 2008 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  4. Jani Hautakorpi, Gonzalo Camarillo, and David López. Framework for decentralising legacy applications. International Journal of Grid and Utility Computing (IJGUC), Special Issue, 10 pages, accepted for publication. © 2010 Inderscience Enterprises. By permission.
  5. Jani Hautakorpi and Jouni Mäenpää. 2010. Load balancing for structured P2P networks using the Advanced Finger Selection Algorithm (AFSA). In: Sung Y. Shin, Sascha Ossowski, Michael Schumacher, Mathew J. Palakal, and Chih-Cheng Hung (editors). Proceedings of the 25th Annual ACM Symposium on Applied Computing (SAC 2010). Sierre, Switzerland. 22-26 March 2010. New York, NY, USA. ACM. Pages 655-662. ISBN 978-1-60558-638-0. © 2010 Association for Computing Machinery (ACM). By permission.
  6. Jani Hautakorpi and Göran Schultz. 2010. A feasibility study of an arbitrary search in structured Peer-to-Peer networks. In: Proceedings of the 19th International Conference on Computer Communications and Networks (ICCCN 2010). Zürich, Switzerland. 2-5 August 2010. IEEE. 8 pages. ISBN 978-1-4244-7115-7. © 2010 Institute of Electrical and Electronics Engineers (IEEE). By permission.

Keywords: peer-to-peer, distributed hash table, interconnection, decentralization, load balancing, search

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Last update 2018-01-10