A.It is used for PIM control traffic
B.It is optionally configured for a high bandwidth multicast source to reduce multicast traffic replication to uninterested PE routers
C.Within the VPF configuration in the PE router， multiple Default MDT groups are configured so each VPF can support multiple multicast sources
D.There is a reduced multicast state in the MPLS core P routers
E.When multicast traffic exceeds a certain configured threshold， traffic from the Data MDT is switched to the Default MDT to conserve bandwidth

A.Logging detect fail-login
B.Login on-failure log
C.Login detect login-failure log
D.Logging login on-failure
E.none of the above

A.GFC-4 bits of generic flow control
B.Forward-explicit congestion notification（FECN）
C.VCI-16 bits of virtual channel identifier
D.CLP-1 bit of congestion loss
E.HEC-8 bit of header error control
F.ATM Discard Eligibility（DE）bit

A.lowest cost
B.highest bandwidth
C.lowest hop-count
D.path attributes
E.lowest delay

A.It prevents message looping，Session Advertisement（SA）messages must be RPF checked
B.RPF check should be done against the route to the Rendez-vous Point of the corresponding PIM-SM domain，which originated the SA
C.RPF checking Session Advertisement（SA）messages will cause message looping
D.RPF check should be done against the route to the source S of the corresponding PIM-SM domain