RFC 1034:DOMAIN NAMES - CONCEPTS AND FACILITIES
RFC-Ref

Unavailable


Click on the red underlined text to get to the source

... the domain system rather than guaranteeing that all copies are simultaneously updated. When updates are unavailable due to network or host ...


... against the master, but may also optionally perform these operations against other secondary servers. This strategy can improve the transfer process when the primary is unavailable due to host downtime or network ...



Google
Web
RFC-Ref