Which mechanisms can be used to secure NTP? (Choose two.)

MD5 authentication keys are a standard mechanism in NTP to ensure the authenticity and integrity of NTP packets. This prevents unauthorized NTP servers from providing time updates and protects against tampering with time synchronization messages. Access-group configuration (ACLs) can be applied to network devices to filter NTP traffic based on source IP address, destination IP address, and port numbers. This restricts which devices can send or receive NTP packets, thereby controlling access to the NTP service and preventing unauthorized time synchronization or denial-of-service attacks. IPSec communication is a broader security protocol suite that can secure various IP-based communications, but it's not a native or specific NTP security mechanism like MD5 authentication. While IPSec could encapsulate NTP traffic, it's not the primary or most direct way NTP itself is secured. Role-based access control (RBAC) is a security model for managing user permissions, not for securing network protocols like NTP directly.