Traffic Mapping

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for providing to user devices identifiers of edge servers from which to obtain content. One example system includes a traffic control service. The traffic control service is configured to receive polling requests from user devices. In response to a particular polling request, the traffic control service obtains aggregated data about the user devices and edge servers. The traffic control service selects, based on the aggregated data, a best edge server for the user device that sent the particular polling request. The traffic control service sends an identifier of the selected best edge server to the user device.