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Scanning for Non-Broadcast SSIDs

  • Artigo

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.

 

An access point (AP) or peer station can be configured to exclude the service set identifier (SSID) in the SSID information element (IE) of any broadcast 802.11 Beacon or Probe Response frames. For example, an AP could exclude its SSID by either setting the Length or SSID fields of the SSID IE to zero.

When the 802.11 station receives an 802.11 Beacon or Probe Response with an excluded SSID, the station must follow these guidelines:

  • If the 802.11 station is performing an explicit scan operation through a set of OID_DOT11_SCAN_REQUEST, the station must resolve excluded SSIDs as part of the scan operation. In this situation, the 802.11 station resolves an excluded SSID from the list of SSIDs specified through the udot11SSIDsOffset member of the DOT11_SCAN_REQUEST_V2 structure.

  • If the 802.11 station is performing an implicit scan operation, the station can optionally resolve excluded SSIDs. If the 802.11 station attempts to resolve excluded SSIDs, it must follow these guidelines:

    • When OID_DOT11_SCAN_REQUEST is set, the 802.11 station must cache the list of SSIDs specified through the udot11SSIDsOffset member.
    • When performing the implicit scan operation, the 802.11 station must only resolve excluded SSIDs from the cached list of SSIDs.

Note  If the uNumOfdot11SSIDs member of the DOT11_SCAN_REQUEST_V2 structure has a value of zero, the 802.11 station must not attempt to resolve excluded SSIDs when performing a scan operation.

 

The 802.11 station resolves the excluded SSID by sending an 802.11 Probe Request frame with the SSID IE set to the value of an SSID specified through the udot11SSIDsOffset member. The 802.11 station can either:

  • Send the Probe Request frame directly to the AP or peer station from which the station received the Beacon or Probe Response frame with the excluded SSID.

  • Broadcast the Probe Request frame to the BSS network from which the station received the Beacon or Probe Response frame with the excluded SSID.