请求终端或数据站标识本身或指示其状态的过程.

The process of requesting a terminal or data station to identify itself or to indicate status.

当传输媒体正忙时，为避免与进行中的传输发生碰撞，某一数据站延迟其传输的一种过程。

A process by which a data station delays its transmission when the transmission medium is busy to avoid collision with ongoing transmission.