A wide range of traffic engineering and troubleshooting tasks rely on reliable, timely, and detailed traffic measurements. We describe a passive packet measurement framework that is (a) general enough to serve as the basis for a wide range of operational tasks, and (b) relies on a small set of primitives that facilitate uniform deployment in router interfaces or dedicated measurement devices, even at very high speeds. This document describes the motivation for such a framework through several operational examples, defines the measurement primitives (filtering, sampling, and hashing), and illustrates their use.