Typically,an IP address refers to an individual host on a particular network.IP also accommodates addresses that refer to a grou

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问题 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 stations on the LAN.
⑤处应填入?

选项 A、multicast
B、unicast
C、broadcast
D、multiple unicast

答案C

解析 通常,一个IP地址指向某网络上的一个主机。IP同时也具有指向一个或多个网络中的一组主机的地址形式,这种地址称为多播地址,而将分组从一个源点发送到一个多播组所有成员的行为称为多播。在单个局域网段范围内的多播操作相当简单。IEEE 802和其他局域网协议都包括了对MAC层多播地址的支持。当一个具有多播地址的分组在某个局域网段上传输时,相应多播组的成员都能识别出这个多播地址,并接受该分组。在这种情况下,只需要传输一个分组副本。这种技术之所以能行之有效,是因为局域网本身具有广播特性:来自任何一个站点上的传输都会被局域网中的所有其他站点接收到。
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