The EDNS0 Client Subnet (ECS) feature will be a key function as networks are pushing more content to the edge of their network spread out through the width of their network. At the same time, IPv4 space is being "optimized" to gain greater utilization with longer (/25, /26, & /27 prefixes) which are spread throughout the network. This means DNS resolver solutions (rDNS) which scale to the longer prefixes, IPv6, and will be required. Akamai's AnswerX rDNS solutions provide proven ECS scalability. These slides have been presented to several Operators over the few months. These are shared her to facilitate their download and exploration.
Are you interested in AnswerX? You can request a trial download from Getting Started with AnswerX - Downloading and Drive Testing