Node Evaluation in the Chord P2P Systems

• Published in: 2009 Fourth International Conference on Dependability of Computer Systems pp. 168 - 175
• Main Authors: Cichon, J., Cichon, K., Kobylanski, P.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.06.2009
• Subjects: beta distribution; Chord; Computer science; Fingers; Mathematics; Maximum likelihood estimation; Moment methods; Peer to peer computing; peer-to-peer system; Protocols; Random variables; Software engineering; statistical estimators; Video sharing
• ISBN: 9780769536743; 0769536743
• DOI: 10.1109/DepCoS-RELCOMEX.2009.32

A peer-to-peer (P2P) computing is a common and promissing paradigm of software engineering for construction of decentralized system within an available technology. P2P networks are useful for such purposes as sharing content files containing audio, video, data or anything in digital format. We concentrate our attention on such P2P systems which are decentralized and structured. A typical example of such system is Chord. Recent investigations of P2P systems shows that the problem of its reliability should be considered very carefully since, for example, the existing solutions have a tendency of loosing stored documents. The proposed solutions of this unwanted phenomena requires a knowledge of some global parameters of systems, such as number of nodes, number of information items (documents) stored in a system or the average lifetime on nodes in the system. In this paper we investigate two statistical estimators for the number of nodes in the Chord peer-to-peer system and one estimator for the number of information items stored in the system. The first estimator of the number of nodes is based on the Maximum Likelihood Estimation (MLE) technology and the second is based on the Methods of Moments (MM). We compare its statistical properties, show that the MM estimator has a better properties for our purposes and we discuss how we can implement this estimators in the Chord system. Our solutions can be implemented in Chord in such a way that they do not require any additional transmissions since all necessary information can be gathered during the standard operations of checking consistency of the Chord structure. Our results can be applied not only to the Chord P2P system but can be adopted to other decentralized and structured systems.