Three possible ways of data transmission in CCNA include: 

Simplex: The Communication is unidirectional in Simplex mode, as on a single-direction road. Just one of the two devices on a connection can communicate, the other can just get. The simplex mode can utilize the whole limit of the channel to send information one WAY.

Half Duplex: Each station can transmit and receive in Half-duplex mode, however not simultaneously. At the POINT when one device is sending, the other can just receive, and the other way around. The half-duplex mode is utilized in situations where there is no requirement for communication both ways simultaneously. The whole limit of the channel can be used for every direction.

Full Duplex: Both stations can send and receive all the while in full-duplex mode. Signals that are going in one direction share the CAPACITY of the connection with signals going another way IN this type of mode. This sharing can happen in two ways: 

• Either the connection should contain two truly separate transmission ways, one for sending and the other for receiving. 
• The capacity is split between signals going in two ways. 

Full-duplex mode is utilized when communication both ways are required CONSTANTLY. The limit or capacity of the channel, anyway, should be split between the two directions.