How Amazon Route 53 uses EDNS0 to estimate the location of a user - Amazon Route 53

How Amazon Route 53 uses EDNS0 to estimate the location of a user

To improve the accuracy of geolocation, geoproximity, IP-based, and latency routing, Amazon Route 53 supports the edns-client-subnet extension of EDNS0. (EDNS0 adds several optional extensions to the DNS protocol.) Route 53 can use edns-client-subnet only when DNS resolvers support it:

  • When a browser or other viewer uses a DNS resolver that does not support edns-client-subnet, Route 53 uses the source IP address of the DNS resolver to approximate the location of the user and responds to geolocation queries with the DNS record for the resolver's location.

  • When a browser or other viewer uses a DNS resolver that does support edns-client-subnet, the DNS resolver sends Route 53 a truncated version of the user's IP address. Route 53 determines the location of the user based on the truncated IP address rather than the source IP address of the DNS resolver; this typically provides a more accurate estimate of the user's location. Route 53 then responds to geolocation queries with the DNS record for the user's location.

  • EDNS0 is not applicable to private hosted zones. For private hosted zones Route 53 uses data from the Route 53 Resolvers in the AWS Region that the private hosted zone is in to make geolocation and latency routing decisions.

For more information about edns-client-subnet, see the IETF draft Client Subnet in DNS Requests.