Which protocol would you use to synchronize the VM in the public cloud with an internal time source at your premises?

Network Time Protocol (NTP) is a standardized protocol for network time synchronization. Domain Name System (DNS) is a service that is used to translate a qualified domain name (FQDN) to an IP address. The rsync utility is a Linux/Unix utility used to synchronize (copy) a number of files to a remote system. A virtual private network (VPN) is a private encrypted tunnel that is normally created over a public Internet connection.