CSMA,although more efficient than ALOHA or slotted ALOHA,still has one glaring inefficiency.If the medium is busy,the station will wait for a random amount of time.When two frames collide,the medium remains（ ）for the duration of transmission of both damaged frames.The use of random delays reduces the probability of（ ）.For（请作答此空）frames,compared to propagation time,the amount of wasted capacity can be considerable.This waste can be reduced if a station continues to listen to the medium while（ ）.The maximum utilization depends on the length of the frame and on the（ ）time;the longer the frames or the shorter the propagation time，the higher the utilization.A.longB.shortC.bigD.small
CSMA,although more efficient than ALOHA or slotted ALOHA,still has one glaring inefficiency.If the medium is busy,the station will wait for a random amount of time.When two frames collide,the medium remains（ ）for the duration of transmission of both damaged frames.The use of random delays reduces the probability of（ ）.For（请作答此空）frames,compared to propagation time,the amount of wasted capacity can be considerable.This waste can be reduced if a station continues to listen to the medium while（ ）.The maximum utilization depends on the length of the frame and on the（ ）time;the longer the frames or the shorter the propagation time，the higher the utilization.
A.long
B.short
C.big
D.small
B.short
C.big
D.small
参考解析
解析：尽管CSMA的效率远远大于ALOHA或时隙ALOHA，但它依然存在一个显著低效率的情况。当信道繁忙的时候，站点需要等待一段随机时间。当两个帧发生冲突时，在两个被破坏帧的传输持续时间内，信道仍然无法使用。使用随机时延会降低冲突的可能性。但如果帧的长度相对于传播时间来说很长，那么容量的浪费也是非常可观的。如果站点在传输时还继续监听信道，就能减少这种浪费。最大利用率与帧长和传播时间有关，帧越长或者传播时间越短，利用率就越高。
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