Overview[ edit ] An Ethernet frame including the EtherType field.
Each ether options slot designates an octet; the EtherType is two octets long. In modern implementations of Ethernet, the field within the Ethernet frame used to describe the EtherType can also be used to represent the size of the payload of the Ethernet Frame.
Historically, depending on the type of Ethernet framing that was in use on an Ethernet segment, both interpretations were simultaneously valid, leading to potential ambiguity. That value was chosen because the maximum length MTU of the data field of an Ethernet Thus, values of and below for this field indicate that the field is used as the size of the payload of the Ethernet frame while values of and above indicate that the field is used to represent an EtherType. The interpretation of values —, inclusive, is undefined.
However, as the minimum payload of an Ethernet frame is 46 bytes, a protocol which uses EtherType must include its own length field if that is necessary for the recipient of the frame to determine the length of short packets if allowed for that protocol.
VLAN tagging[ ether options ] Insertion of the The payload following includes a bit tag control identifier TCI followed by an Ethernet frame beginning with a second original EtherType field for consumption by end stations. IEEE The proposition to resolve this conflict was to substitute ether options special EtherType value 0x when a length would otherwise be used.
The chair of IEEE The draft authors also responded to the chair's letter, but no subsequent answer from the IEEE However, for Ethernet, Ethernet II framing is still used.