Typically, an IP address refers to an individual host on a particular network. IP also accommodates addresses that refer to a group of hosts on one or more networks. Such addresses are referred to as multicast addresses, and the act of sending a packet from a source to the members of a （1）group is referred to as multicasting. Multicasting done （2）the scope of a single LAN segment is straightforward. IEEE 802 and other LAN protocols include provision for MAC-level multicast addresses. A packet with a multicast address is transmitted on a LAN Segment. Those stations that are members of the （3）multicast group recognize the multicast address and （4）the packet. In this case, only a single copy of the packet is ever transmitted. This technique works because of the （5）nature of a LAN: A transmission from any one station is received by all other station on the LAN.
空白（4）应选（ ）。
