A.It does not support all underlying unicast routing protocols like BGP
B.Receivers are registered with RP by their first hop router
C.From the RP， traffic flows down a source tree to each receiver.
D.It supports shared trees only， and assumes all hosts want the multicast traffic
E.Receivers are joined to the shared tree by their local designated router

A.After the route target replacement policy is applied to the target router， the BGP session need not be refreshed manually to put the policy into operation.
B.Route Target Rewrite allows the administration of the routing policy to stay local to the AS.
C.Route target replacement is always done by the ASBR.
D.Route target rewrites are supported for VRF export maps.
E.Route target replacement can be done on incoming and outgoing BGP updates.

A.FRR
B.SSO
C.distribute CEF
D.switch virtual path
E.graceful restart

A.FEC might correspond to a destination IP subnet， but it might also correspond to any traffic class that the edge LSR considers significant.
B.FEC is a group of IP packets that is forwarded over a different path， but with the same forwarding treatment.
C.FEC is a group of IP packets that is forwarded over the same path， and with the same forwarding treatment.
D.FEC is a group of IP packets that is forwarded over a different path， but with the different forwarding treatment.
E.FEC is a group of IP packets that is forwarded over the same path， but with a different forwarding treatment

A.the number of subscribers that will be serviced currently and in the future because this affects the number of required PPPoA sessions
B.The types of applications that the NSP offers to the end subscriber
C.The capacity of ATM and Frame Relay interworking on the NSP
D.in the case of more than one user， whether all users need to reach the same final destination orservice，or they all have different service destinations
E.Whether the service provider or the final service destination is providing the IP address to the CPE of the subscriber