When set, the OID_DOT11_FRAGMENTATION_THRESHOLD object identifier (OID) requests that the miniport driver set the value of the IEEE 802.11 dot11FragmentationThreshold management information base (MIB) object to the specified value.
When queried, OID_DOT11_FRAGMENTATION_THRESHOLD requests that the miniport driver return the value of the dot11FragmentationThreshold MIB object.
This MIB object specifies the current maximum size, in bytes, of the MAC protocol data unit (MPDU) frame that the PHY can transmit.
The 802.11 station fragments a MAC service data unit (MSDU) packet if the payload length (plus the 802.11 MAC header and trailer) exceeds the value of dot11FragmentationThreshold.
The data type for OID_DOT11_FRAGMENTATION_THRESHOLD is a ULONG value that specifies the fragmentation threshold in bytes.
The aMPDUMaxLength attribute of the current PHY type on the 802.11 station determines the range of values for the dot11FragmentationThreshold MIB object, and is based on the following formula:
256 <= dot11FragmentationThreshold <= min(2346, aMPDUMaxLength PHY attribute)
When OID_DOT11_FRAGMENTATION_THRESHOLD is set, the 802.11 station must do the following:
After the set request, use the new fragmentation threshold value on all MSDU packets issued by the operating system to the miniport driver's MiniportSendNetBufferLists function.
Either use the new fragmentation threshold value on all MSDU packets that are pending in the station's transmit queue, or continue to use the old fragmentation threshold value for the pending MSDU packets.
When OID_DOT11_FRAGMENTATION_THRESHOLD is set, the 802.11 station must not apply the new fragmentation threshold value on the MSDU packet that the station is transmitting.
The following points apply to a miniport driver operating in Extensible Station (ExtSTA) mode:
If the miniport driver has enabled automatic MAC configuration, it can fail the set request if the 802.11 station manages the MAC-layer configuration. In this situation, the driver returns NDIS_STATUS_DOT11_AUTO_CONFIG_ENABLED from its MiniportOidRequest function.
For more information about the automatic MAC configuration, see OID_DOT11_AUTO_CONFIG_ENABLED.
The current PHY type is determined through the ExtSTA msDot11CurrentPhyID MIB object. This MIB object specifies the index of the current PHY type within the 802.11 station's list of supported PHY types. For more information about msDot11CurrentPhyID, see OID_DOT11_CURRENT_PHY_ID.
The default value for the dot11FragmentationThreshold MIB object depends on the IEEE 802.11 aMPDUMaxLength attribute of the current PHY type on the 802.11 station based on the following formula:
dot11FragmentationThreshold = min(2346, aMPDUMaxLength)
The miniport driver must set the dot11FragmentationThreshold MIB object to this default when all of the following apply:
A set request of OID_DOT11_CURRENT_PHY_ID changes the current PHY type.
The miniport driver initializes the current PHY type through its MiniportInitializeEx function.
A method request of OID_DOT11_RESET_REQUEST is made to reset the MAC layer of the 802.11 station and the bSetDefaultMIB member of the DOT11_RESET_REQUEST structure is TRUE.
For more information about the aMPDUMaxLength PHY attribute, see OID_DOT11_MPDU_MAX_LENGTH.
Note A Native 802.11 miniport driver that is designed to run on the Windows Vista or Windows Server 2008 operating systems must always reset this 802.11 MIB OID to its default value. This is the case regardless of the value of the bSetDefaultMIB member of the DOT11_RESET_REQUEST structure. This requirement applies to a miniport driver that, in a call to the NdisMSetMiniportAttributes function, sets MiniportAttributes -> Native_802_11_Attributes -> Header -> Revision to NDIS_MINIPORT_ADAPTER_802_11_ATTRIBUTES_REVISION_1.
|Available in Windows Vista and later versions of the Windows operating systems.|