Which two statements are true about RPF checks in MSDP（Multicast Source Discovery Protocol）？（）

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