A.點(diǎn)對多點(diǎn)多播業(yè)務(wù) B.點(diǎn)對多點(diǎn)群呼業(yè)務(wù) C.IP多點(diǎn)廣播業(yè)務(wù) D.虛電路業(yè)務(wù)