A hybrid searching scheme in unstructured P2P networks

The existing searching schemes in peer-to-peer (P2P) networks are either forwarding-based or non-forwarding based. In forwarding-based schemes, queries are forwarded from the querying source to the query destination nodes. These schemes offer low state maintenance. However, querying sources do not entirely have control over query processing. In non-forwarding based methods, queries are not forwarded, and the querying source directly probes its neighbors for the desired files. Non-forwarding searching provides querying sources flexible control over the searching process at the cost of high state maintenance. In this paper, we seek to combine the powers of both forwarding and non-forwarding searching schemes. We propose an approach where the querying source directly probes its own extended neighbors, forwards the query to a subset of its extended neighbors, and guides these neighbors to probe their own extended neighbors on its behalf. Our approach can adapt query processing to the popularity of the sought files without having to maintain a large set of neighbors because its neighbors´ neighbors are also in the searching scope due to the 1-hop forwarding inherent in our approach. It achieves higher query efficiency than the forwarding scheme and a better success rate than the non-forwarding approach. To the best of our knowledge, the work in this paper is the first one to combine forwarding and non-forwarding P2P searching schemes. Experimental results demonstrate the effectiveness of our approach.