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