Content Delivery Networks (CDNs) deliver much of the world's web, video, and application content on the Internet today. A key component of a CDN is the mapping system that uses the DNS protocol to route each client's request to a "proximal" server that serves the requested content. While traditional mapping systems identify a client using the IP of its name server, we describe our experience in building and rollingout a novel system called end-user mapping that identifies the client directly by using a prefix of the client's IP address.