Wi-Fi is a Passion


MAC Layer - QoS

In the MAC header, there is also a field that is called the QoS control field, and it has different flags. It is in total a 2-byte field (16 bits). Those 16 bits are written down as followed. The first 4 bits is the Traffic Identifier. This identifies the User Priority. The User Priority is shown in the following screenshot.


When the TID is 0110 (what equals 6) it will be classified as Voice traffic.

The next bit shows if the client is allowed to go to sleep or not. If it is set to ‘1’ then there is no more data for the client and the client can go back to sleep.

The ack policy is a 2-bit field with four options. You have, as in this example, Normal Ack (00), No-ACK (01), No Explicit ACK (10) and the last one is a Block ACK (11).