This illustration shows two rows broken up into segments-the top row represents an original Ethernet frame while the bottom row represents an 802.1Q-tagged Ethernet VLAN frame. Both frames begin with identical segments, labeled (from left to right): "Preamble," "Dest. address," and "Source address." The top frame follows with a narrow segment labeled "Type," and a longer segment labeled "Data." This is followed by ellipses, an unlabeled segment, and a segment labeled "CRC."

After "Source address" in the bottom frame, we see two short segments labeled "Tag Protocol Identifier" and "Tag Control Information." The remainder of the frame is the same as the frame above. Dashed lines connect Preamble to Preamble, and CRC to CRC. They also connect Type in the top frame with Tag Protocol Identifier in the bottom frame, as well as Type in the top frame with Type in the bottom frame.