between computers, and a resulting paradigm shift from centralized to highly distributed systems. With massive scale also comes massive instability, as node and link failures become the norm rather than the exception. For such highly volatile systems, decentralized gossip-based protocols are emerging as an approach to maintaining simplicity and scalability while achieving fault-tolerant information dissemination.

As Peer-to-Peer (P2P) networks become popular, there is an emerging need to collect a variety of statistical summary information about the participating nodes. The P2P networks of today lack mechanisms to compute even such basic aggregates as MIN, MAX, SUM, COUNT or AVG. In this paper, we define and study the NODEAGGREGATION problem that is concerned with aggregating data stored at nodes in the network. We present generic schemes that can be used to compute any of the basic aggregation functions accurately and robustly. Our schemes can be used as building blocks for tools to collect statistics on network topology, user behavior and other node characteristics. This is a STUDENT paper intended as a REGULAR presentation. I.

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