Peer-to-Peer Systems

Peer-to-Peer systems, in contrast to the traditional client-server model do not distinguish between clients and servers: all participating computers are peers. Thus, all participating computers have the capability to act both as servers and as clients at the same time. Within this framework we conduct research and development on how to scale peer-to-peer networks to several millions of nodes while at the same time keeping the network management overhead to tolerable levels. 

Our current efforts focus on studying the locality patterns of p2p systems in order to identify mechanisms that will exploit this locality and improve the overall scalability of such systems. Furthermore, our research contributions revolve around peer-to-peer network probing (tracing) and scalability improvement techniques, such as caching, network reorganization, and semantic proximity. In addition, we study issues concerning p2p network tomography and security of these networks.

Recently, an initiative for a Peer-To-Peer reading group has started. 


  • Harris Papadakis, Paraskevi Fragopoulou, Marios Dikaiakos and Evangelos Markatos. Divide Et Impera: Partitioning Unstructured Peer-to-Peer Systems to Improve Resource Location. 2nd CoreGRID Integration Workshop, October 2006 (to appear)
  • Elias Athanasopoulos, Kostas G. Anagnostakis and Evangelos P. Markatos. Misusing Unstructured P2P Systems to Perform DoS Attacks: The Network that Never Forgets. In Proceedings of the 4th International Conference on Applied Cryptography and Network Security (ACNS'06). June 2006, Singapore. (pdf)
  • Charis Papadakis, Paraskevi Fragopoulou, Elias Athanasopoulos, Marios Dikaiakos, Alexandros Labrinidis, Evangelos Markatos. A Feedback-based Approach to Reduce Duplicate Messages in Unstructured Peer-to-Peer Networks. To appear in Proceedings of the CoreGRID Integration Workshop 2005 ( pdf)
  • Evangelos P. Markatos: Tracing a large-scale Peer to Peer System: an hour in the life of Gnutella. In Proceedings of the CCGrid 2002: the second IEEE International Symposium on Cluster Computing and the Grid, May 2002, pages 65-74. Available: compressed postscript PDF
  • Georgios Portokalidis, Evangelos P. Markatos, Manolis Marazakis, Study and Bridging of Peer-to-Peer File Sharing Systems. Technical Report 321,ICS-FORTH, Heraklion, Crete, Greece, October 2002.Available: (gzipped pdf)




  • Georgios Portokalidis, Study and Bridging of Peer-to-Peer File Sharing Systems, Senior thesis,University of Crete,2002
  • Konstantinos Xinidis, Discovery of the topology of Gnutella network and study of its performance, Senior thesis,University of Crete,2002    ( html doc src)
  • Sofia Papagianaki, The changing world of Gnutella, Senior thesis,University of Crete,2002


Funding is provided by project SecSPeer: Secure and Scalable peer-to-peer computing and communication systems. Funded by the General Secretariat for Research and Technology.