IEEE 802.11 MAC Frame Format
IEEE 802.11 MAC Frame:
The 802.11 standard defines three kinds of frames: data frame, control frame and management frame. The IEEE 802.11 MAC Frame Format for data frame is given below:
Frame Control: This field has 11 subfields.
Version: Version of the protocol used in a cell.
Type: Type of frame (Example – Data, control and management)
Subtype: Subtype of the type (Example – RTS or CTS)
To DS: Whether the frame is coming from the inter-cell distribution system.
MF: Whether more fragments will follow.
Retry: It indicates the retransmission of a frame sent earlier.
Power: It is used by a base station to make the receiver asleep or awake.
More: It indicates that the sender has more frames for the receiver.
W: It specifies that the body has been encrypted using Wired Equivalent Privacy.
O: It tells the receiver that frames with this bit-on must be processed in the order.
Address 1, 2, 3, 4: Two addresses are for source and destination and the remaining two are for base stations for inter-cell communication.
Sequence: It is used for numbering the frames and fragments. 12 bits are used for indicating the frame and the remaining 4 bits are used for indicating the fragment.
Data: This field contains a payload of up to 2312 bytes.
Checksum: This field is used for error detection.
Control Frame: Control Frames have only one or two addresses, no data field and no sequence field. The important field here is the subtype field.
Management Frame: Management Frame has the same structure except without one base station’s address because Management Frames are restricted to a single frame only.