Which three techniques should be used to secure management protocols？（）

A. Configure SNMP with only read-only community strings.
B. Encrypt TFTP and syslog traffic in an IPSec tunnel.
C. Implement RFC 3704 filtering at the perimeter router when allowing syslog access from devices on the outside of a firewall.
D. Synchronize the NTP master clock with an Internet atomic clock.
E. Use SNMP version 2.
F. Use TFTP version 3 or above because these versions support a cryptographic authentication mechanism between peers.