EDNS Client Subnet
EDNS Client Subnet (ECS) is an option in the Extension Mechanisms for DNS that allows a recursive DNS resolver to specify the subnetwork for the host or client on whose behalf it is making a DNS query. This is generally intended to help speed up the delivery of data from content delivery networks, by allowing better use of DNS-based load balancing to select a service address near the client when the client computer is not necessarily near the recursive resolver.
When an authoritative name server receives a DNS query, it takes advantage of ECS DNS extension to resolve the hostname to a CDN which is geolocationally near to the client IP's subnet, hence the client makes further requests to a nearby CDN, thereby reducing latency. The EDNS client subnet mechanism is specified in RFC 7871.
- "How it works". A Faster Internet. Archived from the original on 2018-03-28. Retrieved 2018-03-27.CS1 maint: unfit URL (link)
- "EDNS Client Subnet (ECS) Guidelines | Public DNS | Google Developers". Google Developers. Retrieved 2018-04-02.