802.11 MAC Header Management

Important The Native 802.11 Wireless LAN interface is deprecated in Windows 10 and later. Please use the WLAN Device Driver Interface (WDI) instead. For more information about WDI, see WLAN Universal Windows driver model.

Each packet sent by the 802.11 station through calls to the MiniportSendNetBufferLists function begins with an 802.11 MAC header.

For more information about the format of the 802.11 MAC header, refer to Clause 8.2.1 of the IEEE 802.11-2012 standard.

The following table describes which fields and subfields within the 802.11 MAC header are set by the operating system or 802.11 station.

Field name Subfield name Set by operating system Set by 802.11 station

Frame Control

Protocol Version

X

Frame Control

Type

X

Frame Control

Subtype

X

X

Frame Control

To DS

X

Frame Control

From DS

X

Frame Control

More Fragments

X

Frame Control

Retry

X

Frame Control

Pwr Mgt

X

Frame Control

More Data

X

Frame Control

Protected Frame

X

Frame Control

Order

X

Duration/ID

X

Address 1

X

Address 2

X

Address 3

X

Sequence Control

Fragment Number

X

Sequence Control

Sequence Number

X

Address 4

X

Note The following notes apply to the preceding table: †When operating in safe-mode, miniport drivers should not modify the Protected Frame bit.

The following points apply to the Subtype subfield of the 802.11 MAC header.

  • If the Type subfield is set to zero (management), the operating system will set the Subtype subfield. In this situation, the 802.11 station must not change the value of this subfield.

  • If the Type subfield is set to 2 (data), the operating system will set the Subtype subfield. However, the 802.11 station can change the value of this subfield if it is extending the MAC header to support fields not supported by the operating system. Note If the original value of the Subtype subfield was 4 (null data) and the 802.11 station changes the subfield, the station must use an equivalent "null data" value.

The operating system uses the Address 4 field of the 802.11 MAC header under the following conditions:

  • The 802.11 station has connected to an infrastructure basic service set (BSS) network.

  • After associating with an access point (AP) in the BSS network, the miniport driver makes an NDIS_STATUS_DOT11_ASSOCIATION_COMPLETION indication with the bFourAddressSupported member of the DOT11_ASSOCIATION_COMPLETION_PARAMETERS structure set to TRUE.

  • The From DS and To DS subfields in the MAC header are set to one.

The 802.11 station must update the MAC header to provide any fields from standards or proprietary protocols not supported by the operating system. For more information about this, see Extending Packet Data During Send Operations.