This lesson begins our discussion of Ethernet. We’ll explore how layer 2 networks work and how to configure and manage Ethernet switches. However, first let's take a look at the Ethernet standards.

Why do we need the Ethernet standard?

Ethernet is a family of networking technologies used in local area networks (LANs), which are defined under IEEE 802.2 and 802.3 standards. It is the most widely used LAN technology family today. 

Before we dive in, let's first clarify the question: Why do we need Ethernet standards?

The Ethernet standards ensure that all devices, regardless of manufacturer, can communicate with each other. Without standards, every company could use its own methods for cabling, signaling, and data formats, so devices wouldn’t interoperate, as shown in the diagram below.

Standards guarantee compatibility, simplify design, reduce cost, and help networks scale easily.

What is Ethernet?

Ethernet is a set of networking standards that define how devices in a local area network (LAN) communicate. It covers things like cable types, signaling, data frames, and how devices share the network medium. Ethernet is the most common LAN technology, and it allows computers, switches, and other devices to send and receive data reliably at high speeds.

The most important thing is to understand that Ethernet is not a single standard or protocol; it’s a family of standards. 

Ethernet has evolved over time to support different speeds, cable types, topologies, and features. For example, you’ll see standards for 10 Mbps, 100 Mbps, 1 Gbps, 10 Gbps, and even faster rates. Some Ethernet standards use copper cabling, while others use fiber optics. The IEEE 802.3 working group manages all these variations. This is why Ethernet can fit into so many different environments — from a small home network to a large data center — because all these related standards work together to ensure interoperability and flexibility.

Ethernet and the OSI model

The Ethernet family of protocols operates at both layer 2 (data link layer) and layer 1 (physical layer) of the OSI model. They are defined in the IEEE 802.2 and 802.3 standards.

As shown in the diagram above, Ethernet standards define both Layer 2 and Layer 1 technologies. At the data-link layer, Ethernet relies on two separate sub-layers to operate, the Logical Link Control sublayer and the Media Access Control sublayer.

LLC sublayer

The LLC sublayer is used to communicate with the upper protocol layers of the OSI model. It takes the protocol data units (PDUs) from the upper layers, which are typically IPv4 packets, and adds control information to help deliver the data to its destination.

The LLC sublayer is implemented in software and is hardware agnostic. An example of the LLC can be considered the network driver software of a server's NIC. The NIC driver is a software program that interacts directly with the NIC hardware and passes data between the MAC sublayer and the physical media.

MAC sublayer

MAC constitutes the lower sublayer of the data link layer. The MAC sublayer is implemented in hardware, typically in the server's NIC. The Ethernet MAC sublayer has two primary functions:

• Data Encapsulation and Decapsulation
  • Frame Delimiting
  • Addressing
  • Error detection
• Media Access Control
  • Control of media access
  • Media recovery