The process of communication between nameservers is controlled by the top sections of the zone file, the SOA records and the NS records. When a change is made to the zone file on the primary nameserver, it sends a message or "notify packet" to the other nameservers for the domain, which it finds in the "NS records" of the zone file. When these nameservers receive this notification they reload the zone files from the primary, thus maintaining up to date information so they can function as authoritative nameservers for the domain.