802.11 frame types

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In the IEEE 802.11 wireless LAN protocols (such as Wi-Fi), a MAC frame is constructed of common fields (which are present in all types of frames) and specific fields (present in certain cases, depending on the type and subtype specified in the first octet of the frame).

Contents

Generic 802.11 Frame 802.11 MAC Frame.svg
Generic 802.11 Frame

The very first two octets transmitted by a station are the Frame Control. The first three subfields within the frame control and the last field (FCS) are always present in all types of 802.11 frames. These three subfields consist of two bits Protocol Version subfield, two bits Type subfield, and four bits Subtype subfield.

Frame control

802.11 Frame Control Field 802.11 Frame Control.png
802.11 Frame Control Field

The first three fields (Protocol Version, Type and Subtype) in the Frame Control field are always present. The fields, in their order of appearance in transmission, are:

  1. Protocol Version
  2. Type
  3. Subtype
  4. To-DS
  5. From-DS
  6. More-Fragments
  7. Retry
  8. Power Management
  9. More Data
  10. Protected frame
  11. +HTC/order

Protocol version subfield

The two-bit protocol version subfield is set to 0 for WLAN (PV0) and 1 for IEEE 802.11ah (PV1). The revision level is incremented only when there is a fundamental incompatibility between two versions of the standard. [1] [2] PV1 description is incorporated in the latest 802.11-2020 standard.

Types and subtypes

Various 802.11 frame types and subtypes
Type value

(bits 3–2)

Type

description

Subtype value

(bits 7–4)

Subtype description
00Management0000Association Request
00Management0001Association Response
00Management0010Reassociation Request
00Management0011Reassociation Response
00Management0100Probe Request
00Management0101Probe Response
00Management0110Timing Advertisement
00Management0111Reserved
00Management1000 Beacon
00Management1001ATIM
00Management1010Disassociation
00Management1011Authentication
00Management1100Deauthentication
00Management1101Action
00Management1110Action No Ack (NACK)
00Management1111Reserved
01Control0000–0001Reserved
01Control0010Trigger [3]
01Control0011TACK
01Control0100 Beamforming Report Poll
01Control0101 VHT/HE NDP Announcement
01Control0110Control Frame Extension
01Control0111Control Wrapper
01Control1000 Block Ack Request (BAR)
01Control1001 Block Ack (BA)
01Control1010 PS-Poll
01Control1011 RTS
01Control1100 CTS
01Control1101 ACK
01Control1110CF-End
01Control1111CF-End + CF-ACK
10Data0000Data
10Data0001–0011Reserved
10Data0100Null (no data)
10Data0101–0111Reserved
10Data1000 QoS Data
10Data1001QoS Data + CF-ACK
10Data1010QoS Data + CF-Poll
10Data1011QoS Data + CF-ACK + CF-Poll
10Data1100QoS Null (no data)
10Data1101Reserved
10Data1110QoS CF-Poll (no data)
10Data1111QoS CF-ACK + CF-Poll (no data)
11Extension0000 DMG Beacon
11Extension0001S1G Beacon
11Extension0010–1111Reserved

Action frames

Action frames extend management frames to control a certain action. Some of the action categories are QoS, Block Ack, Public, Radio Measurement, Fast BSS Transition, Mesh Peering Management, etc. These frames are sent by a station when it needs to tell its peer for a certain action to be taken.

For example, a station can tell another station to set up a block acknowledgement by sending an ADDBA Request action frame. The other station would then respond with an ADDBA Response action frame.

Wi-Fi Neighbor Awareness Networking (NAN), also known as Wi-Fi Aware, service discovery frames are NAN-specific public action frames. [4] They are used in Remote ID for example. [5]

ToDS and FromDS

ToDS is one bit in length and set to 1 if destined to Distribution System, [6] while FromDS is a one-bit length that is set to 1 if originated from Distribution System. [6]

Retry

Set to 1 if the Data or Management frame is part retransmission of the earlier frame. This bit is reused for different purpose in Control frame.

Protected frame

Set to 1 if the Management Frame is protected by encryption as described in IEEE_802.11w-2009.

+HTC/order

It is one bit in length and is used for two purposes:

References

  1. ↑ "802.11 frames : A starter guide to learn wireless sniffer traces". community.cisco.com. October 25, 2010. Retrieved February 20, 2019.
  2. ↑ 802.11 Working Group. Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. 2016. New York, NY: IEEE. p. 638.{{cite book}}: CS1 maint: numeric names: authors list (link)
  3. ↑ LAN/MAN Standards Committee (February 9, 2021). IEEE Standard for Information Technology--Telecommunications and Information Exchange between Systems Local and Metropolitan Area Networks--Specific Requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 1: Enhancements for High-Efficiency WLAN. New York, NY: IEEE Standards Association. p. 76. doi:10.1109/IEEESTD.2021.9442429. ISBN   978-1-5044-7390-3.
  4. ↑ EPpatent 3369083B1
  5. ↑ Kais Belwafi; Ruba Alkadi; Sultan A. Alameri; Hussam Al-Hamadi; Abdulhadi Shoufan (2022). "Unmanned Aerial Vehicles' Remote Identification: A Tutorial and Survey". IEEE Access . 10: 87577–87601. doi:10.1109/ACCESS.2022.3199909. ISSN   2169-3536. Wikidata   Q125618419.
  6. 1 2 Rapp, Dale (May 17, 2014). "THE TO DS AND FROM DS FIELDS". DALESWIFISEC. Retrieved August 13, 2019.
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