Ethernet data is encapsulated in frames as shown in the following figure for standard Ethernet frames. The fields in the frame are transmitted from left to right. The bytes within the fields are transmitted from left to right (from least significant bit to most significant bit unless specified otherwise). The Ethernet MAC can handle jumbo Ethernet frames where the data field can be much larger than 1,500 bytes.
The Ethernet MAC can also accept Virtual LAN (VLAN) frames. The VLAN frame format is shown in the following figure. If the frame is a VLAN type frame, the Ethernet MAC accepts four additional bytes.
Ethernet PAUSE/flow control frames can be transmitted and received by the Ethernet MAC. Figure 1 shows how a PAUSE/flow control frame differs from the standard Ethernet frame format. The following subsections describe the individual fields of an Ethernet frame and some basic functionality of the Ethernet MAC.