NetSage is a project to develop a unified open, privacy-aware network measurement, and visualization service to address the needs of today’s international networks. Modern science is increasingly data-driven and collaborative in nature, producing petabytes of data that can be shared by tens to thousands of scientists all over the world. The National Science, Foundation-supported International Research Network Connections (IRNC) links, have been essential to performing these science experiments. Recent deployment of Science DMZs [Dart, E. et al., 2013], both in the US and other countries, is starting to raise expectations for data throughput performance for wide-area data transfers. New capabilities to measure and analyze the capacity of international wide-area networks are essential to ensure end-users are able to take full advantage of such infrastructure. NetSage will provide the network engineering community, both US domestic and international, with a suite of tools and services to more deeply understand: 1) the current traffic patterns across IRNC links, and anticipate growth trends for capacity-planning purposes; 2) the main sources and sinks of large, elephant flows to know where to focus outreach and training opportunities; and 3) the cause of packet losses in the links and how they impact end-to-end performance.