1. Contention in data communications networks occurs when two stations attempt to send data over a shared communications media at the same time. The most common occurrence of this is found with the Ethernet protocol (CSMA/CD). When this occurs, the data on the bus is corrupted and each station must retransmit its data. 2. A condition that arises when two or more data stations attempt to transmit at the same time over a shared channel, or when two data stations attempt to transmit at the same time in two-way alternate communication.