underrun & overrun的解释

Overrun: the receiver hardware is unable to hand received data to a hardware buffer because the input rate exceeds the receivers ability to handle the data. 
（ 由于接口输入速率超过接受方处理能力，导致丢包。）

Underruns: There are no data in the output queue.
(Transmit under run，与 Overrun相反，输出接口的缓存从输出队列中取以数据帧时，没有数据帧，是一种非常少见的硬件异常。)