Control Frames

Question 1

Request to Send (RTS) frame

Answer 1

RTS / CTS function is optional and reduces frame collisions when hidden stations have associations with the same AP.

Station sends a RTS frame to another station as the first phase of a two-way handshake before sending a data frame.

Receiver and transmitter address are both present in the RTS frame.

Question 2

Clear to Send CTS Frame

Answer 2

A station responds to a RTS with a CTS frame, providing clearance for the requesting station to send a data frame.

CTS includes a time value causing all other stations (incl hidden stations) to hold off transmission of frames for a time period necessary for the requesting station to send its frame. This minimizes collisions resulting in higher throughput.

The receiver address is the only address which is present within the CTS frame.

Question 3

Acknowledgement ACK Frame

Answer 3

After receiving a data frame, the receiving station will utilise an error checking process to detect any errors.

The receiving station will send an ACK frame to the sending station if no errors are found.

If the sending station does not receive am ACK after a period of time, it will retransmit the frame.