Privacy and DNS Client Subnet

The architecture of service and content delivery on the Internet has evolved significantly, with Content Delivery Networks (CDNs) bringing content closer to users to reduce costs and improve performance. Routing anycast is a method used for content steering, where common IP addresses are used to direct users to the closest service instance. Anycast has been successful in the Root Zone DNS service. However, recent studies show that mobile clients may not always be directed to the closest server, impacting performance. Cloudflare's 1.1.1.1 DNS resolver uses anycast efficiently. Another approach, Application Server Steering, involves redirecting users to closer service locations based on their assumed location. DNS Steering uses the DNS to select optimal server instances based on user location. The use of EDNS Client Subnet in DNS queries raises privacy concerns by revealing user information to authoritative servers without explicit consent. The level of use of Client Subnet is around 12% globally, with variations across countries. Most users attach a /24 subnet in IPv4 queries. The DNS landscape continues to evolve, balancing performance optimization with user privacy considerations.