Abstract: This paper makes the case for Resilient Overlay Networks (RONs), an application-level routing and packet forwarding service that gives end-hosts and applications the ability to take advantage of network paths that traditional Internet routing cannot make use of, thereby improving their end-to-end reliability and performance. Using RON, nodes participating in a distributed Internet application configure themselves into an overlay network and cooperatively forward packets for each other. Each RON node monitors the quality of the links in the underlying Internet and propagates this information to the other nodes; this enables a RON to detect and react to path failures within several seconds rather than several minutes, and allows it to select application-specific paths based on performance. We argue that RON has the potential to substantially improve the resilience of distributed Internet applications to path outages and sustained overload.