Basic Ethernet

Ethernet is a set of technologies and protocols that are used primarily in LANs. However, Ethernet can also be used in MANs and even WANs. It was first standardized in the 1980s as IEEE 802.3 standard. Since then, it has gone through four generations, as shown in the following chart

Standard Ethernet is also referred to as Basic Ethernet. It uses 10Base5 coaxial cables for communications. Ethernet provides service up to the data link layer. At the data link layer, Ethernet divides the data stream received from the upper layers and encapsulates it into frames, before passing them on to the physical layer.

The main parts of an Ethernet frame are

• Preamble − It is the starting field that provides alert and timing pulse for transmission.
• Destination Address − It is a 6-byte field containing the physical address of destination stations.
• Source Address − It is a 6-byte field containing the physical address of the sending station.
• Length − It stores the number of bytes in the data field.
• Data and Padding − This carries the data from the upper layers.
• CRC − It contains error detection information.

Standard Ethernet has many physical layer implementations. The four main physical layer implementations are shown in the following diagram