问题 单项选择题

最适合从一个源向多个目的地传送多媒体数据流的方式是 (40) ,该方式采用的协议是 (41)

A.IGMP

B.ICMP

C.VRRP

D.IGRP

答案

参考答案:A

解析:试题40~41分析
IP多播(也称多址广播或组播)技术是一种允许一台或多台主机(多播源)发送单一数据包到多台主机(一次的、同时的)的TCP/IP网络技术。多播作为一点对多点的通信,是节省网络带宽的有效方法之一。在网络音频/视频广播的应用中,当需要将一个节点的信号传送到多个节点时,无论是采用重复点对点通信方式,还是采用广播方式,都会严重浪费网络带宽,只有多播才是最好的选择。多播能使一个或多个多播源只把数据包发送给特定的多播组,而只有加入该多播组的主机才能接收到数据包。目前,IP多播技术被广泛应用在网络音频/视频广播、AOD/VOD、网络视频会议、多媒体远程教育、 push技术(如股票行情等)和虚拟现实游戏等方面。多播通信要求多播源节点和目的节点之间的所有路由器必须提供对Internet组管理协议(IGMP)、多播路由协议(如PIM、 DVMRP等)的支持。
当一台主机欲加入某个多播组时,会发出“主机成员报告”的IGMP消息通知多播路由器。当多播路由器接收到发给那个多播组的数据时,便会将其转发给所有的多播主机。多播路由器还会周期性地发出“主机成员查询”的IGMP消息,向子网查询多播主机,若发现某个多播组已没有任何成员,则停止转发该多播组的数据。此外,当支持IGMP的主机退出某个多播组时,还会向路由器发送一条“离开组”的IGMP消息,以通知路由器停止转发该多播组的数据。但只有当子网上所有主机都退出某个多播组时,路由器才会停止向该子网转发该多播组的数据。

完形填空

I still remember the days when I was a youthful student in an engineering school. I lived a casual life, without caring about the future. I smoked, drank with friends and made girl friends. Little did I realize that casualness would certainly lead to loss.

Two years had passed and I was staring down a report card that highlighted FALL in more than half the subjects. I didn’t care, at least not until my dad found about it. You see, I studied In India and unlike the United States where the students are expected to finance their own education, my dad financed me.

Then came the day when my dad found out my habit of smoking. He lost his temper but he just told me, “Son, your allowance is cut in half from this moment on”. It hit me like a roundhouse kick.(回旋踢) from Bruce Lee. I was shocked out of my bones. I couldn’t comprehend how to pay off the debts that I had accumulated in college. I owed everybody money: the grocery store, the bars, the restaurants, my friends, etc. I was living a life filled with credit.

When I went back to college, I knew that if I don’t change the way I live my life I won’t be able to pay everybody off. So I decided to make some changes. I quit smoking, cut off from my friends who led me down the wrong the road, starting hanging out in libraries and reading my engineering books.

One year later, I went from a miserable failure to a magna cum laude(优等成绩). Life was never the same again. This incident made me know that anything is possible if you take action and do something about it, however small or large. Even today it still motivates me when I feel that I’m about to lose or give up. It reminds me that I can do it.

小题1: What kind of life did the author live in the engineering school? (No more than 12 words)                                                     

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小题2: When did the author begin to care about the serious situation? (No more than 14 words)

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小题3:How did his father deal with his son’s problem? (No more than 8 words)

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小题4: What did the author learn from this incident? (No more than 12 words)

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问答题 简答题