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

Ethernet and the OSI model

Ethernet family of protocols operate 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.

Ethernet and the OSI model
Figure 1. Ethernet and the OSI model

As shown in Figure 1, 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.

LLC sublayer is implemented in software, and its implementation 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 the data between the MAC sublayer and the physical media.

MAC sublayer

MAC constitutes the lower sublayer of the data link layer. MAC sublayer is implemented in hardware, typically in the server's NIC. 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

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