Handling churn in less-structured P2P systems
Motivation and Approach
Peer-to-peer (P2P) computing can be defined as the sharing of computer resources and services by direct exchange between the participating nodes. Since Napster's introduction in the late 90s, the area has received increasing attention from the research community and the general public.
Due in part to the autonomous nature of peers, their mutual dependency, and their astoundingly large populations, the transiency of peers (a.k.a. churn) and its implications on the overall system's performance have recently attracted the attention of the community. Measurement studies of deployed P2P systems have reported median session times - the time from the node's joining to its subsequent leaving from the system - varying from one hour to one minute. The implication of such levels of churn on the overall system's performance is directly related to the degree of peers' investment in their neighbors. At the very least, the amount of maintenance-related messages processed by any node would be a function of the stability of the node's neighboring set. Beyond this, and in the context of content distribution and data sharing P2P systems, the degree of replication, the effectiveness of caches, and the spread and satisfaction level of queries will all be affected by how dynamic the peers' population ultimately is.
To address this challenge, we have proposed a number of illustrative query-related strategies and organizational protocols that, by taking into consideration the expected session times of peers (their lifespans), yield systems with performance characteristics more resilient to the natural instability of their environments.
- Fabián E. Bustamante and Yi Qiao. Designing Less-structured P2P Systems for the Expected High Churn. In ACM/IEEE Transactions on Networking, (ToN) 16(3), June 2008.
- Yi Qiao and Fabián E. Bustamante.Elders Know Best - Handling Churn in Less Structured P2P Systems, In Proc. of the Fifth IEEE International Conference on Peer-to-Peer Computing, September 2005.
- Fabián E. Bustamante and Yi Qiao. Friendships that last: Peer lifespan and its role in P2P protocols, In Proc. of the International Workshop on Web Content Caching and Distribution, September-October 2003 (Also published as Tech. Report NWU-CS-03-21).
- Yi Qiao and Fabián E. Bustamante.Elders Know Best: Lifespan-Based Ideas in P2P Systems, In Work-In-Progress, 19th Symposium on Operating Systems Principles, October 2003.
- Peer Lifespan Trace - Trace of the lifespans, or session lengths, of peers in the Gnutella network collected, through active measurement, during March 2003.