Methods, systems, and apparatus, including computer programs encoded on a computer storage medium for Content Delivery Networks Interconnection (CDNI) request routing using the PCP FLOWDATA option. In one aspect, a method includes receiving a request for content, and receiving, from a PCP server, flow characteristics for providing the content, where the PCP server receives the flow characteristics for providing the content from a PCP proxy that receives the flow characteristics from the client device. The method includes transmitting first data for querying the downstream content delivery network (CDN) to determine whether the downstream CDN can provide the content and satisfy the flow characteristics. The method includes receiving a response indicating the ability of the downstream CDN to provide the content and satisfy the flow characteristics, and transmitting second data based on the response, where the client device transmits flow metadata based on the second data to the PCP proxy.