Active probe-based measurements are the foundation for understanding important network path properties such as SLA compliance and available bandwidth. Well-known challenges in active probe-based measurement include the logistics of deploying and managing host-based measurement infrastructures, the load that probe packets place on network resources, the inaccuracy of resultant measurements, and the relatively limited set of features that can be measured. In this paper, we argue that these

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... ges can be addressed through programmable, router-based support for active measurement. While commercial routers today have some basic capabilities for emitting probe packets, these mechanisms are minimal and do not allow the necessary flexibility in the kinds of probing that can be done. We describe a set of functional primitives that enable a wide range of router-based active measurements and would improve and simplify the ability to assess and understand network structure and dynamic network state. We discuss the associated resource requirements and implications of our approach related to configuration, security and privacy. Finally, we support and illustrate the powerful potential of our approach through a series of measurement scenarios and describe our ongoing efforts toward a Click-based implementation of our framework.