Balancing at the Name Layer
Before a user connects, they resolve your domain. DNS based global load balancing answers that lookup with the address of the best site for that user, steering traffic across regions without touching the request path.
How It Decides
- Health so unhealthy sites are removed from answers
- Proximity so users reach a nearby region
- Capacity so a saturated site sheds load to another
- Weights so operators can shift traffic gradually
The resolver returns one of several candidate addresses, and the user connects there.
The TTL Catch
DNS answers are cached by resolvers for their TTL. A long TTL reduces lookups but slows failover, since clients keep using a stale address. A short TTL speeds failover but raises DNS query volume. This makes DNS load balancing coarse grained and a little slow to react.
Why It Still Wins
It works for any protocol, needs no inline proxy, and scales globally, which is why CDNs lean on it heavily.
Key idea
DNS based global load balancing steers users by returning the best site address at resolution time using health, proximity, and capacity, but TTL caching makes it coarse grained and slow to fail over.