2011年11月4日星期五

关于clock skew问题的简短对话


clock skew解决的那个我没看懂 16:51
怎么解决的啊?解释一下? 16:51
Jeromy Fu (jianfu - ENGINEER.SOFTWARE ENGINEERING):
比较绕 16:51
两种情况


Jeromy Fu (jianfu - ENGINEER.SOFTWARE ENGINEERING):
一种,发送端快,接收端慢,那么rel_owd会减少,因为每次计算base owd都是取最小值,所以对结果没影响,right? 16:53
Wilson Chen (weichen2 - ENGINEER.SOFTWARE ENGINEERING):
减少就对结果没影响吗?也有吧? 16:53
把本来的拥塞当成非拥塞了 16:54
Jeromy Fu (jianfu - ENGINEER.SOFTWARE ENGINEERING):
因为计算queuing_owd = current_owd - base_owd
16:54
Wilson Chen (weichen2 - ENGINEER.SOFTWARE ENGINEERING):
base owd和current owd同步减少? 16:54
Jeromy Fu (jianfu - ENGINEER.SOFTWARE ENGINEERING):
16:54
Wilson Chen (weichen2 - ENGINEER.SOFTWARE ENGINEERING):
y 16:55
Jeromy Fu (jianfu - ENGINEER.SOFTWARE ENGINEERING):
另外一种情况,发送端慢,接收端快,那么rel_owd会变大 16:58
如果接收端收到数据包后,再把收到的时间戳带回去到发送端(ack包里),那发送端就能计算逆向的owd, reverse_owd
16:59
对发送端来说,收到ack时,他的角色和第一种情况的接收端是一样的,也就是说,可以准备计算reverse_owd
17:01
Wilson Chen (weichen2 - ENGINEER.SOFTWARE ENGINEERING):
了解 17:01
这个比较复杂 17:01
Jeromy Fu (jianfu - ENGINEER.SOFTWARE ENGINEERING):
那好了,发送端和接收端的时钟偏移是一样的,只是方向不一样而已 17:02
叠加上去就可以了 17:02
Wilson Chen (weichen2 - ENGINEER.SOFTWARE ENGINEERING):
有道理,就是靠reverse_owd

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