Last updated

An Ethernet port on a laptop computer connected to a twisted pair cable with an 8P8C modular connector Ethernet Connection.jpg
An Ethernet port on a laptop computer connected to a twisted pair cable with an 8P8C modular connector
Symbol used by Apple on some devices to denote an Ethernet connection Apple Ethernet Symbol.svg
Symbol used by Apple on some devices to denote an Ethernet connection

Ethernet ( /ˈθərnɛt/ EE-thər-net) is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). [1] It was commercially introduced in 1980 and first standardized in 1983 as IEEE 802.3. Ethernet has since been refined to support higher bit rates, a greater number of nodes, and longer link distances, but retains much backward compatibility. Over time, Ethernet has largely replaced competing wired LAN technologies such as Token Ring, FDDI and ARCNET.


The original 10BASE5 Ethernet uses a thick coaxial cable as a shared medium. This was largely superseded by 10BASE2, which used a thinner and more flexible cable that was both cheaper and easier to use. More modern Ethernet variants use twisted pair and fiber optic links in conjunction with switches. Over the course of its history, Ethernet data transfer rates have been increased from the original 2.94  Mbit/s [2] to the latest 400 Gbit/s, with rates up to 1.6  Tbit/s under development. The Ethernet standards include several wiring and signaling variants of the OSI physical layer.

Systems communicating over Ethernet divide a stream of data into shorter pieces called frames. Each frame contains source and destination addresses, and error-checking data so that damaged frames can be detected and discarded; most often, higher-layer protocols trigger retransmission of lost frames. Per the OSI model, Ethernet provides services up to and including the data link layer. [3] The 48-bit MAC address was adopted by other IEEE 802 networking standards, including IEEE 802.11 (Wi-Fi), as well as by FDDI. EtherType values are also used in Subnetwork Access Protocol (SNAP) headers.

Ethernet is widely used in homes and industry, and interworks well with wireless Wi-Fi technologies. The Internet Protocol is commonly carried over Ethernet and so it is considered one of the key technologies that make up the Internet.


Accton Etherpocket-SP parallel port Ethernet adapter (circa 1990). Supports both coaxial (10BASE2) and twisted pair (10BASE-T) cables. Power is drawn from a PS/2 port passthrough cable. Accton-etherpocket-sp-parallel-port-ethernet-adapter.jpg
Accton Etherpocket-SP parallel port Ethernet adapter (circa 1990). Supports both coaxial (10BASE2) and twisted pair (10BASE-T) cables. Power is drawn from a PS/2 port passthrough cable.

Ethernet was developed at Xerox PARC between 1973 and 1974. [4] [5] It was inspired by ALOHAnet, which Robert Metcalfe had studied as part of his PhD dissertation. [6] [7] The idea was first documented in a memo that Metcalfe wrote on May 22, 1973, where he named it after the luminiferous aether once postulated to exist as an "omnipresent, completely-passive medium for the propagation of electromagnetic waves." [4] [8] [9] In 1975, Xerox filed a patent application listing Metcalfe, David Boggs, Chuck Thacker, and Butler Lampson as inventors. [10] In 1976, after the system was deployed at PARC, Metcalfe and Boggs published a seminal paper. [11] [lower-alpha 1] Yogen Dalal, [13] Ron Crane, Bob Garner, and Roy Ogus facilitated the upgrade from the original 2.94 Mbit/s protocol to the 10 Mbit/s protocol, which was released to the market in 1980. [14]

Metcalfe left Xerox in June 1979 to form 3Com. [4] [15] He convinced Digital Equipment Corporation (DEC), Intel, and Xerox to work together to promote Ethernet as a standard. As part of that process Xerox agreed to relinquish their 'Ethernet' trademark. [16] The first standard was published on September 30, 1980, as "The Ethernet, A Local Area Network. Data Link Layer and Physical Layer Specifications". This so-called DIX standard (Digital Intel Xerox) [17] specified 10 Mbit/s Ethernet, with 48-bit destination and source addresses and a global 16-bit Ethertype-type field. [18] Version 2 was published in November 1982 [19] and defines what has become known as Ethernet II. Formal standardization efforts proceeded at the same time and resulted in the publication of IEEE 802.3 on June 23, 1983. [20]

Ethernet initially competed with Token Ring and other proprietary protocols. Ethernet was able to adapt to market needs and with 10BASE2, shift to inexpensive thin coaxial cable and from 1990, to the now-ubiquitous twisted pair with 10BASE-T. By the end of the 1980s, Ethernet was clearly the dominant network technology. [4] In the process, 3Com became a major company. 3Com shipped its first 10 Mbit/s Ethernet 3C100 NIC in March 1981, and that year started selling adapters for PDP-11s and VAXes, as well as Multibus-based Intel and Sun Microsystems computers. [21] :9 This was followed quickly by DEC's Unibus to Ethernet adapter, which DEC sold and used internally to build its own corporate network, which reached over 10,000 nodes by 1986, making it one of the largest computer networks in the world at that time. [22] An Ethernet adapter card for the IBM PC was released in 1982, and, by 1985, 3Com had sold 100,000. [15] In the 1980s, IBM's own PC Network product competed with Ethernet for the PC, and through the 1980s, LAN hardware, in general, was not common on PCs. However, in the mid to late 1980s, PC networking did become popular in offices and schools for printer and fileserver sharing, and among the many diverse competing LAN technologies of that decade, Ethernet was one of the most popular. Parallel port based Ethernet adapters were produced for a time, with drivers for DOS and Windows. By the early 1990s, Ethernet became so prevalent that Ethernet ports began to appear on some PCs and most workstations. This process was greatly sped up with the introduction of 10BASE-T and its relatively small modular connector, at which point Ethernet ports appeared even on low-end motherboards.[ citation needed ]

Since then, Ethernet technology has evolved to meet new bandwidth and market requirements. [23] In addition to computers, Ethernet is now used to interconnect appliances and other personal devices. [4] As Industrial Ethernet it is used in industrial applications and is quickly replacing legacy data transmission systems in the world's telecommunications networks. [24] By 2010, the market for Ethernet equipment amounted to over $16 billion per year. [25]


An Intel 82574L Gigabit Ethernet NIC, PCI Express x1 card An Intel 82574L Gigabit Ethernet NIC, PCI Express x1 card.jpg
An Intel 82574L Gigabit Ethernet NIC, PCI Express ×1 card

In February 1980, the Institute of Electrical and Electronics Engineers (IEEE) started project 802 to standardize local area networks (LAN). [15] [26] The "DIX-group" with Gary Robinson (DEC), Phil Arst (Intel), and Bob Printis (Xerox) submitted the so-called "Blue Book" CSMA/CD specification as a candidate for the LAN specification. [18] In addition to CSMA/CD, Token Ring (supported by IBM) and Token Bus (selected and henceforward supported by General Motors) were also considered as candidates for a LAN standard. Competing proposals and broad interest in the initiative led to strong disagreement over which technology to standardize. In December 1980, the group was split into three subgroups, and standardization proceeded separately for each proposal. [15]

Delays in the standards process put at risk the market introduction of the Xerox Star workstation and 3Com's Ethernet LAN products. With such business implications in mind, David Liddle (General Manager, Xerox Office Systems) and Metcalfe (3Com) strongly supported a proposal of Fritz Röscheisen (Siemens Private Networks) for an alliance in the emerging office communication market, including Siemens' support for the international standardization of Ethernet (April 10, 1981). Ingrid Fromm, Siemens' representative to IEEE 802, quickly achieved broader support for Ethernet beyond IEEE by the establishment of a competing Task Group "Local Networks" within the European standards body ECMA TC24. In March 1982, ECMA TC24 with its corporate members reached an agreement on a standard for CSMA/CD based on the IEEE 802 draft. [21] :8 Because the DIX proposal was most technically complete and because of the speedy action taken by ECMA which decisively contributed to the conciliation of opinions within IEEE, the IEEE 802.3 CSMA/CD standard was approved in December 1982. [15] IEEE published the 802.3 standard as a draft in 1983 and as a standard in 1985. [27]

Approval of Ethernet on the international level was achieved by a similar, cross-partisan action with Fromm as the liaison officer working to integrate with International Electrotechnical Commission (IEC) Technical Committee 83 and International Organization for Standardization (ISO) Technical Committee 97 Sub Committee 6. The ISO 8802-3 standard was published in 1989. [28]


Ethernet has evolved to include higher bandwidth, improved medium access control methods, and different physical media. The multidrop coaxial cable was replaced with physical point-to-point links connected by Ethernet repeaters or switches. [29]

Ethernet stations communicate by sending each other data packets: blocks of data individually sent and delivered. As with other IEEE 802 LANs, adapters come programmed with globally unique 48-bit MAC address so that each Ethernet station has a unique address. [lower-alpha 2] The MAC addresses are used to specify both the destination and the source of each data packet. Ethernet establishes link-level connections, which can be defined using both the destination and source addresses. On reception of a transmission, the receiver uses the destination address to determine whether the transmission is relevant to the station or should be ignored. A network interface normally does not accept packets addressed to other Ethernet stations. [lower-alpha 3] [lower-alpha 4]

An EtherType field in each frame is used by the operating system on the receiving station to select the appropriate protocol module (e.g., an Internet Protocol version such as IPv4). Ethernet frames are said to be self-identifying, because of the EtherType field. Self-identifying frames make it possible to intermix multiple protocols on the same physical network and allow a single computer to use multiple protocols together. [30] Despite the evolution of Ethernet technology, all generations of Ethernet (excluding early experimental versions) use the same frame formats. [31] Mixed-speed networks can be built using Ethernet switches and repeaters supporting the desired Ethernet variants. [32]

Due to the ubiquity of Ethernet, and the ever-decreasing cost of the hardware needed to support it, by 2004 most manufacturers built Ethernet interfaces directly into PC motherboards, eliminating the need for a separate network card. [33]

Shared medium

Older Ethernet equipment. Clockwise from top-left: An Ethernet transceiver with an in-line 10BASE2 adapter, a similar model transceiver with a 10BASE5 adapter, an AUI cable, a different style of transceiver with 10BASE2 BNC T-connector, two 10BASE5 end fittings (N connectors), an orange vampire tap installation tool (which includes a specialized drill bit at one end and a socket wrench at the other), and an early model 10BASE5 transceiver (h4000) manufactured by DEC. The short length of yellow 10BASE5 cable has one end fitted with an N connector and the other end prepared to have an N connector shell installed; the half-black, half-grey rectangular object through which the cable passes is an installed vampire tap. 10Base5transcievers.jpg
Older Ethernet equipment. Clockwise from top-left: An Ethernet transceiver with an in-line 10BASE2 adapter, a similar model transceiver with a 10BASE5 adapter, an AUI cable, a different style of transceiver with 10BASE2 BNC T-connector, two 10BASE5 end fittings (N connectors), an orange vampire tap installation tool (which includes a specialized drill bit at one end and a socket wrench at the other), and an early model 10BASE5 transceiver (h4000) manufactured by DEC. The short length of yellow 10BASE5 cable has one end fitted with an N connector and the other end prepared to have an N connector shell installed; the half-black, half-grey rectangular object through which the cable passes is an installed vampire tap.

Ethernet was originally based on the idea of computers communicating over a shared coaxial cable acting as a broadcast transmission medium. The method used was similar to those used in radio systems, [lower-alpha 5] with the common cable providing the communication channel likened to the Luminiferous aether in 19th-century physics, and it was from this reference that the name "Ethernet" was derived. [34]

Original Ethernet's shared coaxial cable (the shared medium) traversed a building or campus to every attached machine. A scheme known as carrier-sense multiple access with collision detection (CSMA/CD) governed the way the computers shared the channel. This scheme was simpler than competing Token Ring or Token Bus technologies. [lower-alpha 6] Computers are connected to an Attachment Unit Interface (AUI) transceiver, which is in turn connected to the cable (with thin Ethernet the transceiver is usually integrated into the network adapter). While a simple passive wire is highly reliable for small networks, it is not reliable for large extended networks, where damage to the wire in a single place, or a single bad connector, can make the whole Ethernet segment unusable. [lower-alpha 7]

Through the first half of the 1980s, Ethernet's 10BASE5 implementation used a coaxial cable 0.375 inches (9.5 mm) in diameter, later called thick Ethernet or thicknet. Its successor, 10BASE2, called thin Ethernet or thinnet, used the RG-58 coaxial cable. The emphasis was on making installation of the cable easier and less costly. [35] :57

Since all communication happens on the same wire, any information sent by one computer is received by all, even if that information is intended for just one destination. [lower-alpha 8] The network interface card interrupts the CPU only when applicable packets are received: the card ignores information not addressed to it. [lower-alpha 3] Use of a single cable also means that the data bandwidth is shared, such that, for example, available data bandwidth to each device is halved when two stations are simultaneously active. [36]

A collision happens when two stations attempt to transmit at the same time. They corrupt transmitted data and require stations to re-transmit. The lost data and re-transmission reduces throughput. In the worst case, where multiple active hosts connected with maximum allowed cable length attempt to transmit many short frames, excessive collisions can reduce throughput dramatically. However, a Xerox report in 1980 studied performance of an existing Ethernet installation under both normal and artificially generated heavy load. The report claimed that 98% throughput on the LAN was observed. [37] This is in contrast with token passing LANs (Token Ring, Token Bus), all of which suffer throughput degradation as each new node comes into the LAN, due to token waits. This report was controversial, as modeling showed that collision-based networks theoretically became unstable under loads as low as 37% of nominal capacity. Many early researchers failed to understand these results. Performance on real networks is significantly better. [38]

In a modern Ethernet, the stations do not all share one channel through a shared cable or a simple repeater hub; instead, each station communicates with a switch, which in turn forwards that traffic to the destination station. In this topology, collisions are only possible if station and switch attempt to communicate with each other at the same time, and collisions are limited to this link. Furthermore, the 10BASE-T standard introduced a full duplex mode of operation which became common with Fast Ethernet and the de facto standard with Gigabit Ethernet. In full duplex, switch and station can send and receive simultaneously, and therefore modern Ethernets are completely collision-free.

Repeaters and hubs

A 1990s ISA network interface card supporting both coaxial-cable-based 10BASE2 (BNC connector, left) and twisted-pair-based 10BASE-T (8P8C connector, right) Network card.jpg
A 1990s ISA network interface card supporting both coaxial-cable-based 10BASE2 (BNC connector, left) and twisted-pair-based 10BASE-T (8P8C connector, right)

For signal degradation and timing reasons, coaxial Ethernet segments have a restricted size. [39] Somewhat larger networks can be built by using an Ethernet repeater. Early repeaters had only two ports, allowing, at most, a doubling of network size. Once repeaters with more than two ports became available, it was possible to wire the network in a star topology. Early experiments with star topologies (called Fibernet) using optical fiber were published by 1978. [40]

Shared cable Ethernet is always hard to install in offices because its bus topology is in conflict with the star topology cable plans designed into buildings for telephony. Modifying Ethernet to conform to twisted pair telephone wiring already installed in commercial buildings provided another opportunity to lower costs, expand the installed base, and leverage building design, and, thus, twisted-pair Ethernet was the next logical development in the mid-1980s.

Ethernet on unshielded twisted-pair cables (UTP) began with StarLAN at 1 Mbit/s in the mid-1980s. In 1987 SynOptics introduced the first twisted-pair Ethernet at 10 Mbit/s in a star-wired cabling topology with a central hub, later called LattisNet. [15] [34] :29 [41] These evolved into 10BASE-T, which was designed for point-to-point links only, and all termination was built into the device. This changed repeaters from a specialist device used at the center of large networks to a device that every twisted pair-based network with more than two machines had to use. The tree structure that resulted from this made Ethernet networks easier to maintain by preventing most faults with one peer or its associated cable from affecting other devices on the network.[ citation needed ]

Despite the physical star topology and the presence of separate transmit and receive channels in the twisted pair and fiber media, repeater-based Ethernet networks still use half-duplex and CSMA/CD, with only minimal activity by the repeater, primarily generation of the jam signal in dealing with packet collisions. Every packet is sent to every other port on the repeater, so bandwidth and security problems are not addressed. The total throughput of the repeater is limited to that of a single link, and all links must operate at the same speed. [34] :278

Bridging and switching

Patch cables with patch fields of two Ethernet switches Network switches.jpg
Patch cables with patch fields of two Ethernet switches

While repeaters can isolate some aspects of Ethernet segments, such as cable breakages, they still forward all traffic to all Ethernet devices. The entire network is one collision domain, and all hosts have to be able to detect collisions anywhere on the network. This limits the number of repeaters between the farthest nodes and creates practical limits on how many machines can communicate on an Ethernet network. Segments joined by repeaters have to all operate at the same speed, making phased-in upgrades impossible.[ citation needed ]

To alleviate these problems, bridging was created to communicate at the data link layer while isolating the physical layer. With bridging, only well-formed Ethernet packets are forwarded from one Ethernet segment to another; collisions and packet errors are isolated. At initial startup, Ethernet bridges work somewhat like Ethernet repeaters, passing all traffic between segments. By observing the source addresses of incoming frames, the bridge then builds an address table associating addresses to segments. Once an address is learned, the bridge forwards network traffic destined for that address only to the associated segment, improving overall performance. Broadcast traffic is still forwarded to all network segments. Bridges also overcome the limits on total segments between two hosts and allow the mixing of speeds, both of which are critical to the incremental deployment of faster Ethernet variants.[ citation needed ]

In 1989, Motorola Codex introduced their 6310 EtherSpan, and Kalpana introduced their EtherSwitch; these were examples of the first commercial Ethernet switches. [lower-alpha 9] Early switches such as this used cut-through switching where only the header of the incoming packet is examined before it is either dropped or forwarded to another segment. [42] This reduces the forwarding latency. One drawback of this method is that it does not readily allow a mixture of different link speeds. Another is that packets that have been corrupted are still propagated through the network. The eventual remedy for this was a return to the original store and forward approach of bridging, where the packet is read into a buffer on the switch in its entirety, its frame check sequence verified and only then the packet is forwarded. [42] In modern network equipment, this process is typically done using application-specific integrated circuits allowing packets to be forwarded at wire speed.[ citation needed ]

When a twisted pair or fiber link segment is used and neither end is connected to a repeater, full-duplex Ethernet becomes possible over that segment. In full-duplex mode, both devices can transmit and receive to and from each other at the same time, and there is no collision domain. [43] This doubles the aggregate bandwidth of the link and is sometimes advertised as double the link speed (for example, 200 Mbit/s for Fast Ethernet). [lower-alpha 10] The elimination of the collision domain for these connections also means that all the link's bandwidth can be used by the two devices on that segment and that segment length is not limited by the constraints of collision detection.

Since packets are typically delivered only to the port they are intended for, traffic on a switched Ethernet is less public than on shared-medium Ethernet. Despite this, switched Ethernet should still be regarded as an insecure network technology, because it is easy to subvert switched Ethernet systems by means such as ARP spoofing and MAC flooding.[ citation needed ] [44]

The bandwidth advantages, the improved isolation of devices from each other, the ability to easily mix different speeds of devices and the elimination of the chaining limits inherent in non-switched Ethernet have made switched Ethernet the dominant network technology. [45]

Advanced networking

A core Ethernet switch Coreswitch (2634205113).jpg
A core Ethernet switch

Simple switched Ethernet networks, while a great improvement over repeater-based Ethernet, suffer from single points of failure, attacks that trick switches or hosts into sending data to a machine even if it is not intended for it, scalability and security issues with regard to switching loops, broadcast radiation, and multicast traffic.[ citation needed ]

Advanced networking features in switches use Shortest Path Bridging (SPB) or the Spanning Tree Protocol (STP) to maintain a loop-free, meshed network, allowing physical loops for redundancy (STP) or load-balancing (SPB). Shortest Path Bridging includes the use of the link-state routing protocol IS-IS to allow larger networks with shortest path routes between devices.

Advanced networking features also ensure port security, provide protection features such as MAC lockdown [46] and broadcast radiation filtering, use VLANs to keep different classes of users separate while using the same physical infrastructure, employ multilayer switching to route between different classes, and use link aggregation to add bandwidth to overloaded links and to provide some redundancy.[ citation needed ]

In 2016, Ethernet replaced InfiniBand as the most popular system interconnect of TOP500 supercomputers. [47]


The Ethernet physical layer evolved over a considerable time span and encompasses coaxial, twisted pair and fiber-optic physical media interfaces, with speeds from 1 Mbit/s to 400 Gbit/s. [48] The first introduction of twisted-pair CSMA/CD was StarLAN, standardized as 802.3 1BASE5. [49] While 1BASE5 had little market penetration, it defined the physical apparatus (wire, plug/jack, pin-out, and wiring plan) that would be carried over to 10BASE-T through 10GBASE-T.

The most common forms used are 10BASE-T, 100BASE-TX, and 1000BASE-T. All three use twisted-pair cables and 8P8C modular connectors. They run at 10 Mbit/s, 100 Mbit/s, and 1 Gbit/s, respectively. [50] [51] [52]

Fiber optic variants of Ethernet (that commonly use SFP modules) are also very popular in larger networks, offering high performance, better electrical isolation and longer distance (tens of kilometers with some versions). In general, network protocol stack software will work similarly on all varieties. [53]

Frame structure

A close-up of the SMSC LAN91C110 (SMSC 91x) chip, an embedded Ethernet chip SMSC LAN91C110 ethernet chip.jpg
A close-up of the SMSC LAN91C110 (SMSC 91x) chip, an embedded Ethernet chip

In IEEE 802.3, a datagram is called a packet or frame. Packet is used to describe the overall transmission unit and includes the preamble, start frame delimiter (SFD) and carrier extension (if present). [lower-alpha 11] The frame begins after the start frame delimiter with a frame header featuring source and destination MAC addresses and the EtherType field giving either the protocol type for the payload protocol or the length of the payload. The middle section of the frame consists of payload data including any headers for other protocols (for example, Internet Protocol) carried in the frame. The frame ends with a 32-bit cyclic redundancy check, which is used to detect corruption of data in transit. [54] :sections 3.1.1 and 3.2 Notably, Ethernet packets have no time-to-live field, leading to possible problems in the presence of a switching loop.


Autonegotiation is the procedure by which two connected devices choose common transmission parameters, e.g. speed and duplex mode. Autonegotiation was initially an optional feature, first introduced with 100BASE-TX, while it is also backward compatible with 10BASE-T. Autonegotiation is mandatory for 1000BASE-T and faster.

Error conditions

Switching loop

A switching loop or bridge loop occurs in computer networks when there is more than one Layer 2 (OSI model) path between two endpoints (e.g. multiple connections between two network switches or two ports on the same switch connected to each other). The loop creates broadcast storms as broadcasts and multicasts are forwarded by switches out every port, the switch or switches will repeatedly rebroadcast the broadcast messages flooding the network. Since the Layer 2 header does not support a time to live (TTL) value, if a frame is sent into a looped topology, it can loop forever. [55]

A physical topology that contains switching or bridge loops is attractive for redundancy reasons, yet a switched network must not have loops. The solution is to allow physical loops, but create a loop-free logical topology using the SPB protocol or the older STP on the network switches.[ citation needed ]


A node that is sending longer than the maximum transmission window for an Ethernet packet is considered to be jabbering. Depending on the physical topology, jabber detection and remedy differ somewhat.

Runt frames

See also


  1. The experimental Ethernet described in the 1976 paper ran at 2.94 Mbit/s and has eight-bit destination and source address fields, so the original Ethernet addresses are not the MAC addresses they are today. [12] By software convention, the 16 bits after the destination and source address fields specify a "packet type", but, as the paper says, "different protocols use disjoint sets of packet types". Thus the original packet types could vary within each different protocol. This is in contrast to the EtherType in the IEEE Ethernet standard, which specifies the protocol being used.
  2. In some cases, the factory-assigned address can be overridden, either to avoid an address change when an adapter is replaced or to use locally administered addresses.
  3. 1 2 Unless it is put into promiscuous mode.
  4. Of course bridges and switches will accept other addresses for forwarding the packet.
  5. There are fundamental differences between wireless and wired shared-medium communication, such as the fact that it is much easier to detect collisions in a wired system than a wireless system.
  6. In a CSMA/CD system packets must be large enough to guarantee that the leading edge of the propagating wave of a message gets to all parts of the medium and back again before the transmitter stops transmitting, guaranteeing that collisions (two or more packets initiated within a window of time that forced them to overlap) are discovered. As a result, the minimum packet size and the physical medium's total length are closely linked.
  7. Multipoint systems are also prone to strange failure modes when an electrical discontinuity reflects the signal in such a manner that some nodes would work properly, while others work slowly because of excessive retries or not at all. See standing wave for an explanation. These could be much more difficult to diagnose than a complete failure of the segment.
  8. This one speaks, all listen property is a security weakness of shared-medium Ethernet, since a node on an Ethernet network can eavesdrop on all traffic on the wire if it so chooses.
  9. The term switch was invented by device manufacturers and does not appear in the IEEE 802.3 standard.
  10. This is misleading, as performance will double only if traffic patterns are symmetrical.
  11. The carrier extension is defined to assist collision detection on shared-media gigabit Ethernet.

Related Research Articles

In computer networking, the maximum transmission unit (MTU) is the size of the largest protocol data unit (PDU) that can be communicated in a single network layer transaction. The MTU relates to, but is not identical to the maximum frame size that can be transported on the data link layer, e.g. Ethernet frame.

100BaseVG is a 100 Mbit/s Ethernet standard specified to run over four pairs of category 3 cable. It is also called 100VG-AnyLAN because it was defined to carry both Ethernet and Token Ring frame types.

A network switch is networking hardware that connects devices on a computer network by using packet switching to receive and forward data to the destination device.

Carrier-sense multiple access with collision detection (CSMA/CD) is a medium access control (MAC) method used most notably in early Ethernet technology for local area networking. It uses carrier-sensing to defer transmissions until no other stations are transmitting. This is used in combination with collision detection in which a transmitting station detects collisions by sensing transmissions from other stations while it is transmitting a frame. When this collision condition is detected, the station stops transmitting that frame, transmits a jam signal, and then waits for a random time interval before trying to resend the frame.

<span class="mw-page-title-main">Fiber Distributed Data Interface</span> Standard for data transmission in a local area network

Fiber Distributed Data Interface (FDDI) is a standard for data transmission in a local area network. It uses optical fiber as its standard underlying physical medium, although it was also later specified to use copper cable, in which case it may be called CDDI, standardized as TP-PMD, also referred to as TP-DDI.

<span class="mw-page-title-main">Network topology</span> Arrangement of the elements of a communication network

Network topology is the arrangement of the elements of a communication network. Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including command and control radio networks, industrial fieldbusses and computer networks.

A virtual local area network (VLAN) is any broadcast domain that is partitioned and isolated in a computer network at the data link layer. In this context, virtual, refers to a physical object recreated and altered by additional logic, within the local area network. VLANs work by applying tags to network frames and handling these tags in networking systems – creating the appearance and functionality of network traffic that is physically on a single network but acts as if it is split between separate networks. In this way, VLANs can keep network applications separate despite being connected to the same physical network, and without requiring multiple sets of cabling and networking devices to be deployed.

In the IEEE 802 reference model of computer networking, the logical link control (LLC) data communication protocol layer is the upper sublayer of the data link layer of the seven-layer OSI model. The LLC sublayer acts as an interface between the media access control (MAC) sublayer and the network layer.

The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer provides the functional and procedural means to transfer data between network entities and may also provide the means to detect and possibly correct errors that can occur in the physical layer.

<span class="mw-page-title-main">Medium access control</span> Service layer in IEEE 802 network standards

In IEEE 802 LAN/MAN standards, the medium access control sublayer is the layer that controls the hardware responsible for interaction with the wired, optical or wireless transmission medium. The MAC sublayer and the logical link control (LLC) sublayer together make up the data link layer. The LLC provides flow control and multiplexing for the logical link, while the MAC provides flow control and multiplexing for the transmission medium.

A network segment is a portion of a computer network. The nature and extent of a segment depends on the nature of the network and the device or devices used to interconnect end stations.

<span class="mw-page-title-main">Network interface controller</span> Hardware component that connects a computer to a network

A network interface controller is a computer hardware component that connects a computer to a computer network.

<span class="mw-page-title-main">Medium Attachment Unit</span>

A Medium Attachment Unit (MAU) is a transceiver which converts signals on an Ethernet cable to and from Attachment Unit Interface (AUI) signals.

<span class="mw-page-title-main">Ethernet hub</span> Device for interconnecting Ethernet devices

An Ethernet hub, active hub, network hub, repeater hub, multiport repeater, or simply hub is a network hardware device for connecting multiple Ethernet devices together and making them act as a single network segment. It has multiple input/output (I/O) ports, in which a signal introduced at the input of any port appears at the output of every port except the original incoming. A hub works at the physical layer of the OSI model. A repeater hub also participates in collision detection, forwarding a jam signal to all ports if it detects a collision. In addition to standard 8P8C ("RJ45") ports, some hubs may also come with a BNC or an Attachment Unit Interface (AUI) connector to allow connection to legacy 10BASE2 or 10BASE5 network segments.

<span class="mw-page-title-main">Link aggregation</span> Using multiple network connections in parallel to increase capacity and reliability

In computer networking, link aggregation is the combining of multiple network connections in parallel by any of several methods. Link aggregation increases total throughput beyond what a single connection could sustain, and provides redundancy where all but one of the physical links may fail without losing connectivity. A link aggregation group (LAG) is the combined collection of physical ports.

<span class="mw-page-title-main">Computer network</span> Network that allows computers to share resources and communicate with each other

A computer network is a set of computers sharing resources located on or provided by network nodes. Computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are made up of telecommunication network technologies based on physically wired, optical, and wireless radio-frequency methods that may be arranged in a variety of network topologies.

<span class="mw-page-title-main">Ethernet physical layer</span> Electrical or optical properties between network devices

The physical-layer specifications of the Ethernet family of computer network standards are published by the Institute of Electrical and Electronics Engineers (IEEE), which defines the electrical or optical properties and the transfer speed of the physical connection between a device and the network or between network devices. It is complemented by the MAC layer and the logical link layer.

<span class="mw-page-title-main">Token Ring</span> Technology for computer networking

Token Ring is a computer networking technology used to build local area networks. It was introduced by IBM in 1984, and standardized in 1989 as IEEE 802.5.

In computer networking, an Ethernet frame is a data link layer protocol data unit and uses the underlying Ethernet physical layer transport mechanisms. In other words, a data unit on an Ethernet link transports an Ethernet frame as its payload.

The 5-4-3 rule, also referred to as the IEEE way, is a design guideline for Ethernet computer networks covering the number of repeaters and segments on shared-medium Ethernet backbones in a tree topology. It means that in a collision domain there should be at most 5 segments tied together with 4 repeaters, with up to 3 mixing segments. Link segments can be 10BASE-T, 10BASE-FL or 10BASE-FB. This rule is also designated the 5-4-3-2-1 rule with there being two link segments and one collision domain.


  1. Ralph Santitoro (2003). "Metro Ethernet Services – A Technical Overview" (PDF). Archived from the original (PDF) on December 22, 2018. Retrieved January 9, 2016.
  2. Xerox (August 1976). "Alto: A Personal Computer System Hardware Manual" (PDF). Xerox. p. 37. Archived (PDF) from the original on September 4, 2017. Retrieved August 25, 2015.
  3. Charles M. Kozierok (September 20, 2005). "Data Link Layer (Layer 2)". Archived from the original on May 20, 2019. Retrieved January 9, 2016.
  4. 1 2 3 4 5 The History of Ethernet. 2006. Archived from the original on December 11, 2021. Retrieved September 10, 2011.
  5. "Ethernet Prototype Circuit Board". Smithsonian National Museum of American History. 1973. Archived from the original on October 28, 2014. Retrieved September 2, 2007.
  6. Gerald W. Brock (September 25, 2003). The Second Information Revolution . Harvard University Press. p.  151. ISBN   0-674-01178-3.
  7. Metz, Cade (March 22, 2023). "Turing Award Won by Co-Inventor of Ethernet Technology". The New York Times. Archived from the original on March 23, 2023. Retrieved March 23, 2023.
  8. Cade Metz (March 13, 2009). "Ethernet — a networking protocol name for the ages: Michelson, Morley, and Metcalfe". The Register. p. 2. Archived from the original on November 8, 2012. Retrieved March 4, 2013.
  9. Mary Bellis. "Inventors of the Modern Computer". Retrieved September 10, 2011.[ permanent dead link ]
  10. U.S. Patent 4,063,220 "Multipoint data communication system (with collision detection)"
  11. Robert Metcalfe; David Boggs (July 1976). "Ethernet: Distributed Packet Switching for Local Computer Networks" (PDF). Communications of the ACM . 19 (7): 395–405. doi:10.1145/360248.360253. S2CID   429216. Archived (PDF) from the original on March 15, 2016. Retrieved August 25, 2015.
  12. John F. Shoch; Yogen K. Dalal; David D. Redell; Ronald C. Crane (August 1982). "Evolution of the Ethernet Local Computer Network" (PDF). IEEE Computer. 15 (8): 14–26. doi:10.1109/MC.1982.1654107. S2CID   14546631. Archived (PDF) from the original on August 15, 2011. Retrieved April 7, 2011.
  13. Pelkey, James L. (2007). "Yogen Dalal". Entrepreneurial Capitalism and Innovation: A History of Computer Communications, 1968–1988. Archived from the original on September 5, 2019. Retrieved September 5, 2019.
  14. "Introduction to Ethernet Technologies". WideBand Products. Archived from the original on April 10, 2018. Retrieved April 9, 2018.
  15. 1 2 3 4 5 6 von Burg, Urs; Kenney, Martin (December 2003). "Sponsors, Communities, and Standards: Ethernet vs. Token Ring in the Local Area Networking Business" (PDF). Industry & Innovation. 10 (4): 351–375. doi:10.1080/1366271032000163621. S2CID   153804163. Archived from the original (PDF) on December 6, 2011. Retrieved February 17, 2014.
  16. Charles E. Spurgeon (February 2000). "Chapter 1. The Evolution of Ethernet". Ethernet: The Definitive Guide. ISBN   1565926609. Archived from the original on December 5, 2018. Retrieved December 4, 2018.
  17. "Ethernet: Bridging the communications gap". Hardcopy . March 1981. p. 12.
  18. 1 2 Digital Equipment Corporation; Intel Corporation; Xerox Corporation (September 30, 1980). "The Ethernet, A Local Area Network. Data Link Layer and Physical Layer Specifications, Version 1.0" (PDF). Xerox Corporation. Archived (PDF) from the original on August 25, 2019. Retrieved December 10, 2011.{{cite journal}}: Cite journal requires |journal= (help)
  19. Digital Equipment Corporation; Intel Corporation; Xerox Corporation (November 1982). "The Ethernet, A Local Area Network. Data Link Layer and Physical Layer Specifications, Version 2.0" (PDF). Xerox Corporation. Archived (PDF) from the original on December 15, 2011. Retrieved December 10, 2011.{{cite journal}}: Cite journal requires |journal= (help)
  20. "IEEE 802.3 'Standard for Ethernet' Marks 30 Years of Innovation and Global Market Growth" (Press release). IEEE. June 24, 2013. Archived from the original on January 12, 2014. Retrieved January 11, 2014.
  21. 1 2 Robert Breyer; Sean Riley (1999). Switched, Fast, and Gigabit Ethernet. Macmillan. ISBN   1-57870-073-6.
  22. Jamie Parker Pearson (1992). Digital at Work. Digital Press. p. 163. ISBN   1-55558-092-0.
  23. Rick Merritt (December 20, 2010). "Shifts, growth ahead for 10G Ethernet". E Times. Archived from the original on January 18, 2012. Retrieved September 10, 2011.{{cite journal}}: Cite journal requires |journal= (help)
  24. "My oh My – Ethernet Growth Continues to Soar; Surpasses Legacy". Telecom News Now. July 29, 2011. Archived from the original on November 18, 2011. Retrieved September 10, 2011.
  25. Jim Duffy (February 22, 2010). "Cisco, Juniper, HP drive Ethernet switch market in Q4". Network World. International Data Group. Archived from the original on August 11, 2019. Retrieved August 11, 2019.
  26. Vic Hayes (August 27, 2001). "Letter to FCC" (PDF). Archived from the original (PDF) on July 27, 2011. Retrieved October 22, 2010. IEEE 802 has the basic charter to develop and maintain networking standards... IEEE 802 was formed in February 1980...
  27. IEEE 802.3-2008, p.iv
  28. "ISO 8802-3:1989". ISO. Archived from the original on July 9, 2015. Retrieved July 8, 2015.
  29. Jim Duffy (April 20, 2009). "Evolution of Ethernet". Network World. Archived from the original on June 11, 2017. Retrieved January 1, 2016.
  30. Douglas E. Comer (2000). Internetworking with TCP/IP – Principles, Protocols and Architecture (4th ed.). Prentice Hall. ISBN   0-13-018380-6. 2.4.9 – Ethernet Hardware Addresses, p. 29, explains the filtering.
  31. Iljitsch van Beijnum (July 15, 2011). "Speed matters: how Ethernet went from 3Mbps to 100Gbps... and beyond". Ars Technica . Archived from the original on July 9, 2012. Retrieved July 15, 2011. All aspects of Ethernet were changed: its MAC procedure, the bit encoding, the wiring... only the packet format has remained the same.
  32. Fast Ethernet Turtorial, Lantronix, December 9, 2014, archived from the original on November 28, 2015, retrieved January 1, 2016
  33. Geetaj Channana (November 1, 2004). "Motherboard Chipsets Roundup". PCQuest. Archived from the original on July 8, 2011. Retrieved October 22, 2010. While comparing motherboards in the last issue we found that all motherboards support Ethernet connection on board.
  34. 1 2 3 Charles E. Spurgeon (2000). Ethernet: The Definitive Guide . O'Reilly. ISBN   978-1-56592-660-8.
  35. Heinz-Gerd Hegering; Alfred Lapple (1993). Ethernet: Building a Communications Infrastructure . Addison-Wesley. ISBN   0-201-62405-2.
  36. Ethernet Tutorial – Part I: Networking Basics, Lantronix, December 9, 2014, archived from the original on February 13, 2016, retrieved January 1, 2016
  37. Shoch, John F.; Hupp, Jon A. (December 1980). "Measured performance of an Ethernet local network". Communications of the ACM. ACM Press. 23 (12): 711–721. doi:10.1145/359038.359044. ISSN   0001-0782. S2CID   1002624.
  38. Boggs, D.R.; Mogul, J.C. & Kent, C.A. (September 1988). "Measured capacity of an Ethernet: myths and reality" (PDF). DEC WRL. Archived (PDF) from the original on March 2, 2012. Retrieved December 20, 2012.{{cite journal}}: Cite journal requires |journal= (help)
  39. "Ethernet Media Standards and Distances". Archived from the original on June 19, 2010. Retrieved October 10, 2017.
  40. Eric G. Rawson; Robert M. Metcalfe (July 1978). "Fibemet: Multimode Optical Fibers for Local Computer Networks" (PDF). IEEE Transactions on Communications. 26 (7): 983–990. doi:10.1109/TCOM.1978.1094189. Archived (PDF) from the original on August 15, 2011. Retrieved June 11, 2011.
  41. Urs von Burg (2001). The Triumph of Ethernet: technological communities and the battle for the LAN standard. Stanford University Press. p. 175. ISBN   0-8047-4094-1. Archived from the original on January 9, 2017. Retrieved September 23, 2016.
  42. 1 2 Robert J. Kohlhepp (October 2, 2000). "The 10 Most Important Products of the Decade". Network Computing. Archived from the original on January 5, 2010. Retrieved February 25, 2008.
  43. Nick Pidgeon (April 2000). "Full-duplex Ethernet". How Stuff Works. Archived from the original on June 4, 2020. Retrieved February 3, 2020.
  44. Wang, Shuangbao Paul; Ledley, Robert S. (October 25, 2012). Computer Architecture and Security: Fundamentals of Designing Secure Computer Systems. John Wiley & Sons. ISBN   978-1-118-16883-7. Archived from the original on March 15, 2021. Retrieved October 2, 2020.
  45. "Token Ring-to-Ethernet Migration". Cisco. Archived from the original on July 8, 2011. Retrieved October 22, 2010. Respondents were first asked about their current and planned desktop LAN attachment standards. The results were clear—switched Fast Ethernet is the dominant choice for desktop connectivity to the network
  46. David Davis (October 11, 2007). "Lock down Cisco switch port security". Archived from the original on July 31, 2020. Retrieved April 19, 2020.
  47. "HIGHLIGHTS – JUNE 2016". June 2016. Archived from the original on January 30, 2021. Retrieved February 19, 2021. InfiniBand technology is now found on 205 systems, down from 235 systems, and is now the second most-used internal system interconnect technology. Gigabit Ethernet has risen to 218 systems up from 182 systems, in large part thanks to 176 systems now using 10G interfaces.
  48. "[STDS-802-3-400G] IEEE P802.3bs Approved!". IEEE 802.3bs Task Force. Archived from the original on June 12, 2018. Retrieved December 14, 2017.
  49. "1BASE5 Medium Specification (StarLAN)". December 28, 1996. Archived from the original on July 10, 2015. Retrieved November 11, 2014.
  50. IEEE 802.3 14. Twisted-pair medium attachment unit (MAU) and baseband medium, type 10BASE-T including type 10BASE-Te
  51. IEEE 802.3 25. Physical Medium Dependent (PMD) sublayer and baseband medium, type 100BASE-TX
  52. IEEE 802.3 40. Physical Coding Sublayer (PCS), Physical Medium Attachment (PMA) sublayer and baseband medium, type 1000BASE-T
  53. IEEE 802.3 4.3 Interfaces to/from adjacent layers
  54. "802.3-2012 – IEEE Standard for Ethernet" (PDF). IEEE Standards Association. December 28, 2012. Archived from the original on February 23, 2014. Retrieved February 8, 2014.
  55. "Layer 2 Switching Loops in Network Explained". ComputerNetworkingNotes. Archived from the original on January 8, 2022. Retrieved January 8, 2022.
  56. IEEE 802.3 8.2 MAU functional specifications
  57. IEEE 802.3 Jabber function requirements
  58. IEEE 802.3 Jabber function
  59. IEEE 802.3 9.6.5 MAU Jabber Lockup Protection
  60. IEEE 802.3 Timers
  61. IEEE 802.3 Timers
  62. IEEE 802.3 Receive jabber functional requirements
  63. IEEE 802.1 Table C-1—Largest frame base values
  64. "Troubleshooting Ethernet". Cisco. Archived from the original on March 3, 2021. Retrieved May 18, 2021.

Further reading