Implementing a Distributed Peer to Peer File Sharing System ... - Umbc

CHEWBACCA Baker, Fink, Trimm, Whisman
Abstract
We implemented a distributed, peer-to-peer file system in Java using the Chord protocol
for efficient location of files stored across a network. Chord is a distributed key lookup
technique that scales logarithmically with an increase in the number of storage nodes.
Initially, we discovered problems with the Chord algorithms, and prototyped corrections
to verify the changes. To implement the file sharing system, a Sockets-based messaging
framework was implemented in Java, using command line interfaces and an FTP-like file
push/pull semantics. The file system enables distributed peers to present a virtual single
directory to users while sharing file load across different platforms. Using the
application, we verified the claimed messaging performance of the basic Chord algorithm
to be close to Mlog(N) behavior in an average case. The algorithms were modified to do
locally-optimal balanced node joins, and experiments showed a 20% improvement in
load balancing fairness over the standard, unbalanced algorithms. We designed
algorithm modifications to support concurrent joins and leaves of the Chord cloud using a
variant on Raymond’s tree-based distributed mutual exclusion algorithm, and informally
proved some safety and liveness properties of the implemented balance and proposed
token-based mutual exclusion algorithms. During the investigation, several
improvements were suggested for the Chord-based file system, including distributed
mutual exclusion with quorum voting, security, replication, and other enhancements.
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