Architecture of Classic Ethernet

Ethernet is a set of technologies and protocols that are used primarily in LANs. It was first standardized in the 1980s as the IEEE 802.3 standard. Ethernet is classified into two categories: classic Ethernet and switched Ethernet.

Classic Ethernet is the original form of Ethernet that provides data rates between 3 to 10 Mbps. The varieties are commonly referred to as 10BASE-X. Here, 10 is the maximum throughput (10 Mbps), BASE denotes use of baseband transmission, and X is the type of medium used.

Architecture

Classic Ethernet is the simplest form of Ethernet. It comprises an Ethernet medium composed of a long piece of coaxial cable acting as a shared transmission medium. Stations connect to the coaxial cable using a card called the network interface (NI). The NIs are responsible for receiving and transmitting data through the network.

Repeaters are used to make end-to-end joins between cable segments as well as regenerate the signals if they weaken. When a station is ready to transmit, it places its frame on the cable. This arrangement is called a broadcast bus because all stations share the same communication medium.

Frame Format of Classic Ethernet

The frame format defines how data is structured for transmission over the network. The main fields of a classic Ethernet frame are:

• Preamble − An 8-byte starting field that provides alert and timing pulses for transmission synchronization.

• Destination Address − A 6-byte field containing the physical address of the destination station.

• Source Address − A 6-byte field containing the physical address of the sending station.

• Type − A 2-byte field that instructs the receiver which process to give the frame to.

• Data − A variable-sized field that carries the data from the upper layers. The maximum size of the data field is 1500 bytes.

• Padding − Added to the data to bring its length to the minimum requirement of 46 bytes.

• CRC − Cyclic Redundancy Check contains error detection information for the entire frame.

Key Characteristics

• Shared medium − All stations share the same coaxial cable, creating potential collisions.

• CSMA/CD protocol − Uses Carrier Sense Multiple Access with Collision Detection to manage access to the shared medium.

• Bus topology − Linear arrangement with terminators at both ends to prevent signal reflection.

Conclusion

Classic Ethernet provides a simple broadcast bus architecture using coaxial cable as a shared medium. Its standardized frame format ensures reliable data transmission with error detection, though the shared medium creates collision issues that modern switched Ethernet addresses.