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【简答题】
考虑在一条链路上传送文件的一个简单协议。在经过某种初始协商之后，A给B发送1KB大小的数据分组，B然后用一个确认应答。A在发送下一个数据分组之前总是要等待前一个ACK(确认)，这就是通常所说的停止一等待协议。在一个预定的时间内未收到确认的分组，就认为是丢失了，并且进行重发。(a)在不会有分组丢失或重复的情况下，说明为什么在分组头中包含“序列号”是不必要的?(b)假定链路可能偶尔地丢失分组，但分组总是以发送的顺序到达接收方。为了让A和B能够检测到和重发丢失的分组，使用2位作序列号够用吗?1位怎么样?(c)现在假定链路可能投递无序，有时候1个分组的投递可能用1分钟时间，有若干分组随之后到达。这会怎样改变对序列号的需求?
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举一反三
【单选题】—May I speak to Miss Brown , Please? — ____________
A.
Who are you?
B.
Who’s this?
C.
This is Miss Brown .
D.
My name is Kate Brown.
【判断题】Addressing forms like “Miss Mary”, “Brown” by the Chinese may be a form. of cultural compromise.()
A.
正确
B.
错误
【单选题】The students ______ busily when Miss Brown went to geta book she ______ in the office.
A.
had written left
B.
were writing hasleft
C.
had written had left
D.
were writing had left
【单选题】Miss Brown is the ______president, though her title is secretary.
A.
sole
B.
ultimate
C.
virtual
D.
comparative
【简答题】This is Miss Brown. Her name is Alice Brown. She is from America. Her telephone number is 8257-6632. She is from America. She is nice. She is a good teacher. I like(喜欢) Miss Brown very much. 根据短文内容，完成...
【简答题】2 弹簧下面悬挂质量为50 g的物体,物体沿竖直方向的运动学方程为 x=2sin10t,平衡位置为势能零点(时间单位:s, 长度单位:cm)。(1) 求弹簧的劲度系数,(2) 求最大动能,(3)求总能。
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