802.11 Frames
802.11 Frame Format
| 2 bytes | 2 bytes | 6 bytes | 6 bytes | 6 bytes | 2 bytes | 6 bytes | 2 bytes | 4 bytes | variable size | 4 bytes |
|---|---|---|---|---|---|---|---|---|---|---|
| Frame Control (FC) | Duration/ID | Address 1 | Address 2 | Address 3 | Sequence Control | Address 4 | QoS Control | HT Control | Data (Frame Body) | FCS |
- Frame Control (FC)
- Message type and subtype
- Duration/ID (DUR)
- EITHER the time in microseconds the channel will be dedicated for transmission of the frame
- OR an identifier for the connection (association)
- Addresses (ADD1-4)
- Up to 4 address can be included, though which ones and their order varies
- Destination address (DA) - Final recipient
- Source Address (SA) - Original sender
- Receiver Address (RA) - Immediate recipient
- Transmitter address (TA) - Immediate sender
- NOTE: the 4th address is only present when communicating with devices on the Distribution System (DS)
- Computers, servers, other APs, etc.
- Up to 4 address can be included, though which ones and their order varies
- Sequence Control (SEQ)
- Used to reassemble fragments and eliminate duplicate frames
- QoS Control (QOS)
- Used to prioritize certain traffic
- HT (High Throughput) Control (HT/HTC)
- Added to 802.11n to enable High Throughput operations
- 802.11n is also known as HT Wi-Fi
- 802.11ac is also known as Very HT (VHT) Wi-Fi
- Added to 802.11n to enable High Throughput operations
- Frame Body (DATA)
- You know what it is
- FCS (frame check sequence) (FCS)
- Same as ethernet header, checks for errors
802.11 Frame Format MNEMONIC
Fuck DurID 123 Seek 4 Cuz Hate Data FUCKS
- FC and DUR(ation)/ID are first
- Addresses 1, 2, 3 SEQ 4 (1 2 3 SEEK 4)
- ??? (QoS and HT)
- PROFIT: DATA and FCS come last
- HT FCS (Hate Fucks) are 4 bytes, Addresses are 6 bytes, the rest are 2 bytes