Distributed Hash Tables (DHTs) have been widely adopted in many Internet-scale P2P systems. Emerging P2P applications such as massively multi player online games (MMOGs) and P2P catalog systems frequently update data or issue multi-dimensional range queries, but existing DHT-based P2P systems can not support these applications efficiently due to object declustering. Object declustering can result in significant inefficiencies in data update and multidimensional range query routing. In this paper, we propose CISS, a framework that supports efficient object clustering for DHT-based P2P applications. While utilizing DHT as a basic lookup layer, CISS uses a Locality Preserving Function (LPF) instead of a hash function. Thus, CISS achieves a high level of clustering without requiring any changes to existing DHT implementations. Technically, we study LPF encoding function, efficient routing protocols for data updates and multi-dimensional range queries, and cluster-preserving load balancing....