Polling: Asking a series of terminals, or checking a series of buffers, one by one, to see if they have data to transmit. A technique for determining who gets to transmit data next.

• 轮询:逐个地询问一组终端或检查一组缓冲区,看看它们是否有数据要发送。一种确定下一个该谁发送数据的技术。