A.only implemented between Cisco source and destination-capable devices
B.statistics provided by syslog， CLI， and SNMP
C.measures delay， jitter， packet loss， and voice quality
D.only monitors VoIP traffic flows
E.provides active monitoring
F.provides passive monitoring

A.Test major changes before deployment and defer minor changes until during deployment. 
B.Document and verify rollback procedures.
C.Ensure consistency of code versions across the network.
D.Progressively modify procedures and documentation during implementation.