Ethernet is a family of wired networking technologies used to connect computers, servers, switches, routers, printers, access points, storage systems and other networked devices. It defines mechanisms for transmitting digital data over physical network links and forms one of the principal technologies used in local area networks. Ethernet can operate over copper twisted-pair cabling, fibre-optic cabling and other physical media, with different standards providing different speeds and physical characteristics.
Common Ethernet speeds include 100 megabits per second, 1 gigabit per second, 2.5 gigabits per second, 5 gigabits per second, 10 gigabits per second and much higher rates in enterprise and data-centre environments. Ethernet is fundamentally a Layer 2 technology in the OSI conceptual model, while IP operates at a higher networking layer. An Ethernet network can therefore carry IP traffic but is not itself synonymous with the Internet or with IP networking.
Traditional Ethernet identifies devices on a local network using Media Access Control addresses, commonly called MAC addresses. A MAC address is associated with a network interface and is used for local frame delivery. Ethernet transmits data in units called frames, which contain fields including source and destination MAC addresses and an indication of the encapsulated protocol. A network switch examines these addresses and forwards frames through appropriate ports rather than indiscriminately sending every frame everywhere.
Modern switched Ethernet networks are predominantly full-duplex, meaning devices can transmit and receive simultaneously without the collision behaviour associated with early shared Ethernet networks. This differs from the original Ethernet model, which used a shared medium and Carrier Sense Multiple Access with Collision Detection, or CSMA/CD. The widespread adoption of switched full-duplex Ethernet made those historical collision-management mechanisms largely unnecessary in ordinary modern switched networks.
Ethernet can use several physical media. Twisted-pair copper Ethernet is extremely common in offices and homes and generally uses modular connectors commonly called RJ45, although the formal connector terminology can be more specific. Categories of twisted-pair cable such as Cat5e, Cat6 and Cat6A specify electrical characteristics relevant to different Ethernet applications. Fibre Ethernet uses optical transceivers and fibre cables and is widely used for longer distances, higher speeds, backbone connections and electrically noisy environments.
Different Ethernet standards specify combinations of speed, encoding, signalling, cable characteristics and maximum distances. The physical layer determines how bits are represented electrically or optically, while the Ethernet framing system determines how data is organised into local network frames. This separation allows Ethernet to evolve to much higher speeds while retaining fundamental concepts such as frame-based local delivery and MAC addressing.
Ethernet switches are central to modern local Ethernet networks. A switch maintains information about which MAC addresses are reachable through its ports and uses this information to forward frames efficiently. If a destination address is unknown, a frame may initially be flooded within the relevant broadcast domain so that the destination can respond and its location can be learned. Switches can support features such as VLANs, link aggregation, Quality of Service, port security, spanning-tree mechanisms and management interfaces.
VLANs allow one physical switching infrastructure to support multiple logically separated Layer 2 networks. Routers perform a different function by forwarding packets between IP networks. In a typical home network, an Ethernet switch or the integrated switching functionality in a router connects wired devices, while the router provides the boundary between the local network and other networks such as an Internet service provider's network.
Ethernet is widely valued for predictable performance, low latency and reliability. A wired Ethernet connection is generally less susceptible to radio-frequency interference and wireless congestion than Wi-Fi. It is commonly used for desktop computers, servers, network-attached storage, gaming systems, access points, security cameras, industrial equipment and infrastructure links. Power over Ethernet, commonly called PoE, allows compatible Ethernet cabling to carry both network data and electrical power to devices such as wireless access points, IP cameras and VoIP telephones. Different PoE standards support different power levels and negotiation mechanisms. Ethernet can therefore provide both connectivity and power through a single cable in appropriate installations. Cable length, electromagnetic conditions, connector quality and the capabilities of network interfaces remain relevant to actual reliability and performance.
Ethernet's origins can be traced to work at Xerox PARC in the 1970s, where Robert Metcalfe and colleagues developed an early form of Ethernet networking. The technology initially used a shared coaxial cable and later evolved through twisted-pair and fibre implementations. Ethernet standards became associated with the IEEE 802.3 family, which has continued to define new physical and data-link technologies as networking requirements have increased.
The transition from shared coaxial networks to switched twisted-pair networks dramatically changed how Ethernet was deployed. Speeds increased from early megabit implementations through Fast Ethernet and Gigabit Ethernet to multi-gigabit and high-speed data-centre Ethernet. Despite these changes, Ethernet remains one of the foundational technologies for wired computer networking because its standards have evolved without abandoning the core frame-based networking model.
Ethernet should not be confused with the Internet. Ethernet can connect devices within a local network, whereas the Internet is a global interconnected system of networks using Internet protocols and routing. Ethernet is also distinct from Wi-Fi, although both commonly carry IP traffic and can connect devices to the same local network. Another misconception is that Ethernet always means one specific speed.
A home computer connected through a gigabit interface and a data-centre server connected through a 400-gigabit optical link can both be using Ethernet while operating at radically different rates. Similarly, an Ethernet cable does not inherently guarantee a particular throughput because the network interfaces, cable category, switch ports, negotiated link mode and traffic conditions all matter.
Ethernet remains important because it provides a scalable foundation for networks ranging from small home LANs to enormous data centres. Modern Ethernet can support very high bandwidth and sophisticated switching architectures while maintaining interoperability through standardised protocols. Technologies such as fibre Ethernet enable long-distance backbone links, while copper Ethernet remains economical for typical room and building connections. Ethernet's relatively deterministic physical medium is particularly useful for infrastructure where stable latency and throughput are important. Industrial variants can incorporate specialised requirements for harsh environments and real-time communication. The term Ethernet consequently describes a broad standards family rather than one cable or one speed, with its common purpose being the reliable exchange of framed digital data across compatible network links.
