2. 计算机
  3. In multipoint networks，there are three persistence methods when a station finds a channel busy．In the 1-persistent method，after

In multipoint networks，there are three persistence methods when a station finds a channel busy．In the 1-persistent method，after

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问题 In multipoint networks，there are three persistence methods when a station finds a  channel busy．In the 1-persistent method，after the station finds the line idle，it sends its frame  immediately．This method has the ________________ chance of collision because two or more stations  may find the line ________________ and send their frames immediately．In the nonpersistent method，a  station that has a frame to send  ________________ the line．If the line is idle．it sends immediately．If the  line is not idle, it waits a  ________________ amount of time and then senses the line again．The  nonpersistent approach ________________ the chance of collision because it is unlikely that two or more  stations will wait the same amount of time and retry to send simultaneously．The p-persistent  approach combines the advantages of the other two strategies．It reduces the chance of collision and improves efficiency．
选项 A、increases
B、equalizes
C、reduces
D、cancels
答案C
解析     在多点接入网络中，当一个站点发现信道繁忙时，采用三种坚持方法。在1坚持方法中，当站点发现线路空闲后，立即发送帧。由于两个或多个站点可能同时发现线路空闲，并立即发送帧，因此该方法具有最高的冲突概率。在非坚持方法中，需要发送帧的站点监听线路，如果线路空闲，则立即发送。如果线路不是空闲的，它会随机等待一段时间，然后再次监听线路。非坚持的方法降低了冲突的可能性，因为两个或多个站点不太可能等待相同的时间后同时发送帧。P坚持的方法综合了前面两种方法的优点，它不但降低了冲突的可能性，还提高了效率。
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