Select the protocol you want the storage system to use to synchronize time. Valid values are:
ntp
SNTP (simple network time protocol) is the preferred protocol because it is the more accurate of the two. You can get a list of public NTP (network time protocol) time servers (used for SNTP) from the NTP.Servers Web at http://ntp.isc.org/bin/view/Servers/WebHome.
Simple network time protocol (NTP) is specified in the RFC 2030 standard and is provided only on UDP port 123.
rdate
If you cannot access an SNTP server, you can use rdate. Many Unix servers can function as an rdate server; see your system administrator to set up or identify an rdate server in your environment.
Also known as the TIME protocol, rdate is specified in the RFC 868 standard. This standard allows for time services to be provided on TCP or UDP port 37. The system uses only UDP port 37.