单项选择题 MVC(Model—View—Controller,模型—视图—控制器)是一种广泛流行的软件设计模式,也是J2EE平台上推荐的一种设计模型。其中,______主要表现用户界面,______用来描述核心业务逻辑。 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 71 group is referred to as multicasting. Multicasting done 72 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 73 multicast group recognize the multicast address and 74 the packet. In this case, only a single copy of the packet is ever transmitted. This technique works because of the 75 nature of a LAN: A transmission from any one station is received by all other station on the LAN.