Answering by location
A global service often runs servers in several regions. Geo DNS routing returns a different address depending on where the request appears to originate, steering each user toward a nearby region to cut latency.
How the decision is made
- The authoritative DNS server inspects the source of the query, usually the address of the resolver asking on the user's behalf.
- It maps that source to a geographic region.
- It returns the address of the closest or policy chosen server set.
A key inaccuracy is that the authoritative server sees the resolver's location, not the user's. A user pointed at a distant public resolver can be routed poorly. The EDNS client subnet extension partly fixes this by passing a truncated portion of the user's address along with the query, giving the authoritative server a better hint while preserving some privacy. Geo routing also enables compliance use cases, keeping certain users on servers within a required jurisdiction.
Key idea
Geo DNS routing returns location aware answers to steer users to a nearby region, with EDNS client subnet improving accuracy when the resolver is far from the user.