Definition: Ethernet is a physical and data link layer technology for local area networks (LANs). Ethernet was invented by engineer Robert Metcalfe.
When first widely deployed in the 1980s, Ethernet supported a maximum theoretical data rate of 10 megabits per second (Mbps). Later, so-called “Fast Ethernet” standards increased this maximum data rate to 100 Mbps. Gigabit Ethernet technology further extends peak performance up to 1000 Mbps, and 10 Gigabit Ethernet technology also exists.
Higher level network protocols like Internet Protocol (IP) use Ethernet as their transmission medium. Data travels over Ethernet inside protocol units called frames.
The run length of individual >Ethernet cables is limited to roughly 100 meters, but Ethernet networks can be easily extended to link entire schools or office buildings using network bridge devices.
The first experimental version of Ethernet wired networking ran at a connection speed of 2.94 megabits per second (Mbps) in 1973. By the time Ethernet became an industry standard in 1982, its speed rating increased to 10 Mbps due to improvements in the technology. Ethernet kept this same rating for more than ten years. Different forms of the standard were named starting with the number ten, including 10-Base2 and 10-BaseT.
The technology colloquially called Fast Ethernet was introduced starting in the mid-1990s. It picked up that name as Fast Ethernet standards support a maximum data rate of 100 Mbps, ten times faster than traditional Ethernet. Other common names for this new standard included 100-BaseT2 and 100-BaseTX.
Fast Ethernet was widely deployed as the need for greater LAN performance became critical to universities and businesses. A key element of its success was its ability to coexist with existing network installations. Mainstream network adapters of the day were built to support both traditional and Fast Ethernet. These so-called “10/100” adapters sense the line speed automatically and adjust connection data rates accordingly.
Just as Fast Ethernet improved on traditional Ethernet, Gigabit Ethernet improved on Fast Ethernet, offering rates up to 1000 Mbps. Although 1000-BaseX and 1000-BaseT versions were created in the late 1990s, it took many more years for Gigabit Ethernet to reach large-scale adoption due to its higher cost.
10 Gigabit Ethernet operates at 10,000 Mbps. Standard versions including 10G-BaseT were produced starting in the mid-2000s. Wired connections at this speed were only cost-effective in certain specialized environments like high-performance computing and some datacenters. 40 Gigabit Ethernet technology has also been under active development for some years.
Maximum Speed versus Actual Speed
The speed ratings of Ethernet have been criticized for being unachievable in real-word usage. Similar to the fuel efficiency ratings of automobiles, network connection speed ratings are calculated under ideal conditions that do not necessarily represent normal operating environments. It is not possible to exceed these speed ratings as they are maximum values.
There is no one specific percentage or formula that can be applied to the maximum speed rating to calculate how an Ethernet’s connection will perform in practice. Actual performance depends on many factors, including line interference or collisions that require applications to re-transmit messages sometimes. Because network protocols consume some amount of network capacity just to support the protocol headers, applications cannot get 100% just for themselves. It is also much more difficult for applications to fill a 10 Gbps connection with data than to fill a 10 Mbps connection. However, with the right applications and communication patterns, actual data rates can reach well over 90% of the theoretical maximum during peak usage.