Computing an answer to a DNS query
- Decides which data center the answer should come from
- Computes the answer based on the chosen data center
How the data center is chosen depends on the property type. For performance properties, Global Traffic Management usually chooses the data center closest to the requester (if it is up, and not overloaded). A data center that is considered down is never chosen. If all data centers are down, then Global Traffic Management considers them all up.
After Global Traffic Management chooses a data center, it computes the answer based on the data center chosen. In the common case in which you have configured a number of server IPs in the data center, all of the servers IPs that are considered up are potentially included in the answer. Because the size of a DNS response packet is limited, if more than eight servers are up, Global Traffic Management chooses eight IP addresses at random for the answer. This random choice is made again for each query, so over a large number of queries, the answers tend to distribute evenly over all of the live servers in the data center.