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= Ethernet Encapsulation and De-encapsulation =

Ethernet encapsulation describes the process by which an 802.11 MPDU wraps a full Ethernet frame for transmission while Ethernet de-encapsulation describes the reverse. The 802.11-2012 standard describes this process in Annex P, "the Integration Function." The process is slightly different depending whether the device performing the action is an access point or station.

== Access Point ==

||  [[Image(wiki:802.11/files:AP_encap.png, width=600)]]  ||
||  '''AP Encapsulation and De-encapsulation'''  ||

The above figure shows how an AP encapsulates and de-encapsulates different types of Ethernet frames.

=== Encapsulation ===

When an AP encapsulates a packet, it treats the destination address in that Ethernet frame as the receiver address (addr1) in the outgoing wireless MPDU. The source address of the Ethernet frame, however, is not the transmitter address (addr2) of the outgoing wireless MPDU -- the TA address must be the wireless MAC address (or BSSID) of the AP. Instead, the source address of the Ethernet frame is put into the third address location (addr3) of the outgoing 802.11 header.

=== De-encapsulation ===

De-encapsulation at the AP recognizes that a station must include the BSSID of the AP as the first argument of the 802.11 header. This receiver address (addr1) is not the destination address of the Ethernet frame. Instead, the destination address is included in the third address location (addr3) of the incoming 802.11 header. The transmitter address (addr2) is the source address of the Ethernet frame that should be generated.

== Station ==

||  [[Image(wiki:802.11/files:STA_encap.png, width=600)]]  ||
||  '''STA Encapsulation and De-encapsulation'''  ||