说明：  “多播”亦称“多点传送”（M u l t i c a s t i n g），是一种让数据从一个成员送出，然后复制给其 他多个成员的技术
("multicast" also known as "multicast" (M u l t i c a s t i n g), is a way to let members of data from a given, and then copied to a number of other members of the technology)