Efficient Search in Unbalanced, Randomized Peer-To-Peer Search Trees

Scalable mechanisms to support efficient key-based search in distributed systems are an important part of the infrastructure of peer-to-peer systems and global information systems. They received substantial attention both in information and communication systems research. A particularly important class of approaches is based on a principle of scalable distribution of binary search trees that has been introduced by Plaxton [9]. When adapting the shape of such a tree search structure to the data distribution in order to obtain load balancing, the search trees may become highly unbalanced. We show that for P-Grid, a Plaxton-like distributed search structure that we first introduced in [1], the expected communication cost for searches is strictly limited by where is the number of peers. This result is completely independent of the shape of the underlying tree. The approach exploits the randomization principle of the P-Grid structure by virtue of its decentralized and randomized construction process.