14.3 WIRED LOCAL AREA NETWORKS (ETHERNET)

In contemporary networking, Ethernet forms the universal foundation of wired local area networks. While earlier LAN technologies such as Token Ring and FDDI once competed for enterprise deployment, Ethernet has achieved near-total dominance across access, distribution, and core layers of modern networks.

Originally conceived as a shared-medium bus network using carrier-sense multiple access with collision detection (CSMA/CD), Ethernet has evolved into a high-speed, switched, full-duplex architecture capable of supporting multi-gigabit and terabit data rates. Today’s Ethernet networks no longer rely on shared coaxial segments; instead, they employ structured cabling and fiber-optic links interconnected by intelligent switches that perform frame forwarding based on MAC addresses.

Understanding Ethernet therefore requires both historical context and an appreciation of its modern implementation. The following sections examine the evolution of Ethernet from shared-medium beginnings to switched architectures, describe the Ethernet frame format, and outline the physical media and topological structures used in current deployments.