Ethernet MAC Frames
As shown in Figure 4.3, an Ethernet MAC frame starts with a header that includes its destination and source MAC addresses. It ends in a frame check sequence (FCS) field that contains a CRC code that is used to detect transmission errors.
Figure 4.3. General format of an Ethernet frame.
Preamble and Start Frame Delimiter Patterns
A station transmits two special bit patterns—a preamble and a start frame delimiter—prior to sending a MAC frame. Figure 4.4 shows a MAC frame preceded by its preamble and start frame delimiter.
Figure 4.4. Preamble, start frame delimiter, and MAC frame.
The preamble pattern tells ...