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My understanding is that the 802.11 frame header is an equivalent of ether header. In the ether header, there is an EtherType field that identifies the payload protocol, such as IPv4/IPv6/ARP etc. However in 802.11 frame header, such an identifier does not seem to exist. I can think of two ways L3 protocol can be specified:

  1. default is IPv4, and other protocol packets have to be packaged into an IPv4 packet.
  2. in the payload of 802.11 frame, there is still an ether header.

Is one of the two correct, or is there some other means?

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802.11 uses the same 'core' frame as the other (IEEE) MAC protocols. It just adds a header of its own. It uses the same EtherType field and values.

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    Thanks. I found the following wiki pages helpful. en.wikipedia.org/wiki/IEEE_802.11#Data_frames and en.wikipedia.org/wiki/IEEE_802.2#IPv4,_IPX,_and_802.2_LLC. "Using LLC is compulsory for all IEEE 802 networks with the exception of Ethernet." It turns out that 802.11 frame payload begins with a 802.2 LLC header, and protocols such as ARP/IPv4/IPv6 are specified in either LSAP or SNAP extension fields of the 802.2 LLC header. Ethernet is an exception among 802 family - it can use Ethernet II frame header, and skip LLC sublayer.
    – QnA
    Apr 8 '20 at 14:46

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