protocols that use the control field of the 802.2 layer (such as the NetBIOS Frame protocol, which actually uses the flow-control and acknowledgment features). protocols that require one of the Service Access Point fields of the 802.2 layer to indicate that the payload is for that protocol. protocols that require the length field (because - unlike, for example, IPv4 and IPv6 - they don't have a length field of their own, or anything else to allow the handler for the protocol to distinguish payload from trailer). (I don't have a copy of DIX 2.0, so I don't know whether it speaks of an 8-byte preamble or a 7-byte preamble and 1 byte of SFD.)Īnd the "Ethernet frame" Wikipedia article also says "Many years later, the 802.3x-1997 standard, and later versions of the 802.3 standard, formally approved of both types of framing.", so, as of 1997, frames with a type field and frames with a length field are both "802.3 frames" a better terminology might be "frames with a type field" vs. It's not as if the preamble/SOF will tell you whether there's a type field or a length field - both types of frame begin with 7 bytes of 10101010, followed by 1 byte of 10101011, followed by the destination field, followed by the source field, followed by the 2-byte type/length field, followed by the payload. 
I.e., the only difference in what they say goes on the wire is that DIX calls the 8th byte, the one with 10101011, part of the preamble, while 802.3 calls it the SFD what actually goes on the wire is the same in both specs. The 2000 version of 802.3 says in section 4.2.5 "Preamble generation" that the 7-byte preamble has 7 bytes of 10101010, followed by the Start Frame Delimiter, and says in section 3.2.2 "Start Frame Delimiter (SFD) field" that the SFD is 1 byte of 10101011.
The DIX version 1.0 spec says, in section 7.5.1.3 "Preamble Generation", that the 8-byte preamble has 7 bytes of 10101010 and 1 byte of 10101011. Ethernet ii (aka DIX) not making use of an SOF (start of frame) byte right after the 8-byte preamble whereas ethernet 802.3 has a 7-byte preamble and 1 byte SOF.
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