In this paper we propose a server-based measurement approach that can be deployed in replicated servers within a wide-area enterprise network to provide distributed service to a large number of clients across the Internet. In our approach, each server performs traffic measurement and exchanges the collected metrics with peer servers. This server-based measurement approach consists of three steps: non-intrusive data collection, data analysis and performance metrics generation, and exchange of performance metrics among peer servers. As part of an experimental system we have built, we describe a performance metrics generation tool called Woodpecker, which is designed based on a non-intrusive passive packet capturing mechanism. Experimental results obtained using Woodpecker demonstrate that it is indeed feasible to employ non-intrusive measurement tools to generate the majority of desired performance metrics for dynamic server selection.