Secondary Primary | NOTIFY | | <-------------------------------- | UDP | --------------------------------> | | NOTIFY Response | | | | | | SOA Request | | --------------------------------> | UDP (or part of | <-------------------------------- | a TCP/TLS session) | SOA Response | | | | | | | | IXFR Request | --- | --------------------------------> | | | <-------------------------------- | | | IXFR Response | | | (Zone data) | | | | | TLS | | | session | IXFR Request | | | --------------------------------> | | | <-------------------------------- | | | IXFR Response | | | (Zone data) | ---