Ethernet is a family of frame-based computer networking technologies for local area networks (LANs). In Computer networking, a frame is a Data packet of fixed or variable length which has been encoded by a Data link layer communications protocol for digital A computer network is a group of interconnected Computers. Networks may be classified according to a wide variety of characteristics The name comes from the physical concept of the ether. In the late 19th century " luminiferous aether " (or " ether " meaning light-bearing aether, was the term used to describe a medium for the propagation It defines a number of wiring and signaling standards for the physical layer, through means of network access at the Media Access Control (MAC)/Data Link Layer, and a common addressing format. The Physical Layer is the first level in the seven-layer OSI model of computer networking. The Media Access Control (MAC Data communication protocol sub-layer also known as the Medium Access Control is a sublayer of the Data Link Layer specified in the The Data Link Layer is Layer 2 of the seven-layer OSI model. It responds to service requests from the Network Layer and issues service requests to the
Ethernet is standardized as IEEE 802.3. IEEE 8023 is a collection of IEEE standards defining the Physical layer, and the media access control (MAC sublayer of the Data link layer, The combination of the twisted pair versions of Ethernet for connecting end systems to the network, along with the fiber optic versions for site backbones, is the most widespread wired LAN technology. There are a few standards for Ethernet over twisted pair or Copper -based computer networking physical connectivity methods It has been in use from around 1980 to the present, largely replacing competing LAN standards such as token ring, FDDI, and ARCNET. Token ring Local area network (LAN technology is a local area network protocol which resides at the Data link layer Fiber distributed data interface ( FDDI) provides a standard for Data transmission in a Local area network ARCNET (also CamelCased as ARCnet, an Acronym from Attached Resource Computer NETwork is a Local area network ( LAN) protocol In recent years, Wi-Fi, the wireless LAN standardized by IEEE 802.11, is prevalent in home and small office networks and augmenting Ethernet in larger installations. Wi-Fi (ˈwaɪfaɪ is the trade name for the popular wireless technology used IEEE 80211 is a set of standards for wireless local area network (WLAN computer communication developed by the IEEE LAN/MAN Standards Committee ( IEEE 802
Ethernet was originally developed at Xerox PARC in 1973–1975. PARC (Palo Alto Research Center Inc formerly Xerox PARC, is a Research and development company in Palo Alto California that began as a division of  In 1975, Xerox filed a patent application listing Metcalfe and Boggs, plus Chuck Thacker and Butler Lampson, as inventors ( : Multipoint data communication system with collision detection). Charles P (Chuck Thacker is a technical fellow and computer pioneer Butler W Lampson (born 1943 is a renowned Computer scientist. In 1976, after the system was deployed at PARC, Metcalfe and Boggs published a seminal paper. 
The experimental Ethernet described in that paper ran at 3 Mbit/s, and had 8-bit destination and source address fields, so Ethernet addresses were not the global addresses they are today. In telecommunications Bit rate or Data transfer rate is the average number of Bits characters or blocks per unit time passing between equipment in a data transmission By software convention, the 16 bits after the destination and source address fields were a packet type field, but, as the paper says, "different protocols use disjoint sets of packet types", so those were packet types within a given protocol, rather than the packet type in current Ethernet which specifies the protocol being used.
Metcalfe left Xerox in 1979 to promote the use of personal computers and local area networks (LANs), forming 3Com. He convinced DEC, Intel, and Xerox to work together to promote Ethernet as a standard, the so-called "DIX" standard, for "Digital/Intel/Xerox"; it standardized the 10 megabits/second Ethernet, with 48-bit destination and source addresses and a global 16-bit type field. Digital Equipment Corporation was a pioneering American company in the Computer industry Xerox Corporation ( (name ˈziːrɒks is a global document management company which manufactures and sells a range of color and black-and-white printers, multifunction The standard was first published on September 30, 1980. Events 1399 - Henry IV is proclaimed King of England. 1744 - France and Spain defeat the Year 1980 ( MCMLXXX) was a Leap year starting on Tuesday (link displays the 1980 Gregorian calendar) It competed with two largely proprietary systems, token ring and ARCNET, but those soon found themselves buried under a tidal wave of Ethernet products. Token ring Local area network (LAN technology is a local area network protocol which resides at the Data link layer ARCNET (also CamelCased as ARCnet, an Acronym from Attached Resource Computer NETwork is a Local area network ( LAN) protocol In the process, 3Com became a major company.
Twisted-pair Ethernet systems have been developed since the mid-80s, beginning with StarLAN, but becoming widely known with 10BASE-T. There are a few standards for Ethernet over twisted pair or Copper -based computer networking physical connectivity methods StarLAN was the first implementation of Ethernet Computer networking on Twisted pair wiring There are a few standards for Ethernet over twisted pair or Copper -based computer networking physical connectivity methods These systems replaced the coaxial cable on which early Ethernets were deployed with a system of hubs linked with unshielded twisted pair (UTP), ultimately replacing the CSMA/CD scheme in favor of a switched full duplex system offering higher performance. Twisted pair Cabling is a form of wiring in which two conductors (two halves of a single circuit) are wound together for the purposes of canceling out Carrier Sense Multiple Access With Collision Detection ( CSMA/CD) in Computer networking is a network control protocol in which a A duplex Communication system is a system composed of two connected parties or devices which can communicate with one another in both directions
Ethernet was originally based on the idea of computers communicating over a shared coaxial cable acting as a broadcast transmission medium. The methods used show some similarities to radio systems, although there are fundamental differences, such as the fact that it is much easier to detect collisions in a cable broadcast system than a radio broadcast. The common cable providing the communication channel was likened to the ether and it was from this reference that the name "Ethernet" was derived.
From this early and comparatively simple concept, Ethernet evolved into the complex networking technology that today underlies most LANs. The coaxial cable was replaced with point-to-point links connected by Ethernet hubs and/or switches to reduce installation costs, increase reliability, and enable point-to-point management and troubleshooting. A StarLAN was the first step in the evolution of Ethernet from a coaxial cable bus to a hub-managed, twisted-pair network. The advent of twisted-pair wiring dramatically lowered installation costs relative to competing technologies, including the older Ethernet technologies.
Above the physical layer, Ethernet stations communicate by sending each other data packets, blocks of data that are individually sent and delivered. As with other IEEE 802 LANs, each Ethernet station is given a single 48-bit MAC address, which is used both to specify the destination and the source of each data packet. IEEE 802 refers to a family of IEEE standards dealing with Local area networks and Metropolitan area networks More specifically the IEEE 802 standards are In Computer networking a Media Access Control address ( MAC address) or Ethernet Hardware Address ( EHA) hardware address Network interface cards (NICs) or chips normally do not accept packets addressed to other Ethernet stations. Adapters generally come programmed with a globally unique address, but this can be overridden, either to avoid an address change when an adapter is replaced, or to use locally administered addresses.
Despite the significant changes in Ethernet from a thick coaxial cable bus running at 10 Mbit/s to point-to-point links running at 1 Gbit/s and beyond, all generations of Ethernet (excluding early experimental versions) share the same frame formats (and hence the same interface for higher layers), and can be readily interconnected. In telecommunications Bit rate or Data transfer rate is the average number of Bits characters or blocks per unit time passing between equipment in a data transmission Gigabit Ethernet (GbE or 1 GigE is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second, as defined by the
Due to the ubiquity of Ethernet, the ever-decreasing cost of the hardware needed to support it, and the reduced panel space needed by twisted pair Ethernet, most manufacturers now build the functionality of an Ethernet card directly into PC motherboards, obviating the need for installation of a separate network card. Twisted pair Cabling is a form of wiring in which two conductors (two halves of a single circuit) are wound together for the purposes of canceling out
Ethernet originally used a shared coaxial cable (the shared medium) winding around a building or campus to every attached machine. Coaxial cable is a cable consisting of an inner conductor surrounded by a tubular insulating layer typically made from a flexible material with a high Dielectric constant, all A scheme known as carrier sense multiple access with collision detection (CSMA/CD) governed the way the computers shared the channel. Carrier Sense Multiple Access With Collision Detection ( CSMA/CD) in Computer networking is a network control protocol in which a This scheme was simpler than the competing token ring or token bus technologies. Token ring Local area network (LAN technology is a local area network protocol which resides at the Data link layer Token bus is a network implementing the Token ring protocol over a "virtual ring" on a Coaxial cable. When a computer wanted to send some information, it used the following algorithm:
This can be likened to what happens at a dinner party, where all the guests talk to each other through a common medium (the air). Before speaking, each guest politely waits for the current speaker to finish. If two guests start speaking at the same time, both stop and wait for short, random periods of time (in Ethernet, this time is generally measured in microseconds). The hope is that by each choosing a random period of time, both guests will not choose the same time to try to speak again, thus avoiding another collision. Exponentially increasing back-off times (determined using the truncated binary exponential backoff algorithm) are used when there is more than one failed attempt to transmit. Exponential growth (including Exponential decay) occurs when the growth rate of a mathematical function is proportional to the function's current value In a variety of Computer networks, binary exponential backoff or truncated binary exponential backoff refers to an Algorithm used to space out repeated
Computers were connected to an Attachment Unit Interface (AUI) transceiver, which was in turn connected to the cable (later with thin Ethernet the transceiver was integrated into the network adapter). An Attachment Unit Interface ( AUI) is a 15 pin connection that provides a path between a node's Ethernet interface and the Medium Attachment Unit (MAU A transceiver is a device that has both a Transmitter and a receiver which are combined and share common circuitry or a single housing While a simple passive wire was highly reliable for small Ethernets, it was not reliable for large extended networks, where damage to the wire in a single place, or a single bad connector, could make the whole Ethernet segment unusable. Multipoint systems are also prone to very 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 of why); these could be much more painful to diagnose than a complete failure of the segment. A standing wave, also known as a stationary wave, is a Wave that remains in a constant position Debugging such failures often involved several people crawling around wiggling connectors while others watched the displays of computers running a ping command and shouted out reports as performance changed. Ping is a Computer network tool used to test whether a particular host is reachable across an IP network it is also used to self test the network interface
Since all communications happen on the same wire, any information sent by one computer is received by all, even if that information is intended for just one destination. The network interface card interrupts the CPU only when applicable packets are received: the card ignores information not addressed to it unless it is put into "promiscuous mode". In computing promiscuous mode or promisc mode is a configuration of a Network card that makes the card pass all traffic it receives to the Central processing 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. Use of a single cable also means that the bandwidth is shared, so that network traffic can slow to a crawl when, for example, the network and nodes restart after a power failure.
For signal degradation and timing reasons, coaxial Ethernet segments had a restricted size which depended on the medium used. A network segment is a portion of a Computer network wherein every device communicates using the same Physical layer. For example, 10BASE5 coax cables had a maximum length of 500 meters (1,640 ft). Also, as was the case with most other high-speed buses, Ethernet segments had to be terminated with a resistor at each end. |- align = "center"| |width = "25"| | |- align = "center"| || Potentiometer |- align = "center"| | | |- align = "center"| Resistor| | For coaxial-cable-based Ethernet, each end of the cable had a 50-ohm resistor attached. The ohm (symbol Ω) is the SI unit of Electrical impedance or in the Direct current case Electrical resistance, Typically this resistor was built into a male BNC or N connector and attached to the last device on the bus, or, if vampire taps were in use, to the end of the cable just past the last device. The BNC ( Bayonet Neill Concelman) connector is a very common type of RF connector used for terminating Coaxial cable. The N connector (in full Type N connector) is a threaded RF connector used to join Coaxial cables. A vampire tap (also called a piercing tap is a device for physically connecting a station (i If termination was not done, or if there was a break in the cable, the AC signal on the bus was reflected, rather than dissipated, when it reached the end. An alternating current ( AC) is an Electric current whose direction reverses cyclically as opposed to Direct current, whose direction remains constant This reflected signal was indistinguishable from a collision, and so no communication would be able to take place.
A greater length could be obtained by an Ethernet repeater, which took the signal from one Ethernet cable and repeated it onto another cable. A repeater is an electronic device that receives a signal and Retransmits it at a higher level and/or higher power or onto the other side of an obstruction If a collision was detected, the repeater transmitted a jam signal onto all ports to ensure collision detection. In Telecommunications a jam signal is a signal that carries a 32-bit binary pattern sent by a data station to inform the other stations that they must not Repeaters could be used to connect segments such that there were up to five Ethernet segments between any two hosts, three of which could have attached devices. Repeaters could detect an improperly terminated link from the continuous collisions and stop forwarding data from it. Hence they alleviated the problem of cable breakages: when an Ethernet coax segment broke, while all devices on that segment were unable to communicate, repeaters allowed the other segments to continue working - although depending on which segment was broken and the layout of the network the partitioning that resulted may have made other segments unable to reach important servers and thus effectively useless.
People recognized the advantages of cabling in a star topology, primarily that only faults at the star point will result in a badly partitioned network, and network vendors started creating repeaters having multiple ports, thus reducing the number of repeaters required at the star point. Star networks are one of the most common Computer network topologies. In Packet networking a multiport repeater is the simplest multi-port active device in use Multiport Ethernet repeaters became known as "Ethernet hubs". Network vendors such as DEC and SynOptics sold hubs that connected many 10BASE2 thin coaxial segments. SynOptics Communications was a Santa Clara California -based early Ethernet vendor There were also "multi-port transceivers" or "fan-outs". These could be connected to each other and/or a coax backbone. The best-known early example was DEC's DELNI. Digital Equipment Corporation was a pioneering American company in the Computer industry These devices allowed multiple hosts with AUI connections to share a single transceiver. They also allowed creation of a small standalone Ethernet segment without using a coaxial cable.
Ethernet on unshielded twisted-pair cables (UTP), beginning with StarLAN and continuing with 10BASE-T, was designed for point-to-point links only and all termination was built into the device. Twisted pair Cabling is a form of wiring in which two conductors (two halves of a single circuit) are wound together for the purposes of canceling out There are a few standards for Ethernet over twisted pair or Copper -based computer networking physical connectivity methods StarLAN was the first implementation of Ethernet Computer networking on Twisted pair wiring This changed hubs 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 more reliable by preventing faults with (but not deliberate misbehavior of) one peer or its associated cable from affecting other devices on the network, although a failure of a hub or an inter-hub link could still affect lots of users. Also, since twisted pair Ethernet is point-to-point and terminated inside the hardware, the total empty panel space required around a port is much reduced, making it easier to design hubs with lots of ports and to integrate Ethernet onto computer motherboards.
Despite the physical star topology, hubbed Ethernet networks still use half-duplex and CSMA/CD, with only minimal activity by the hub, primarily the Collision Enforcement signal, in dealing with packet collisions. Every packet is sent to every port on the hub, so bandwidth and security problems aren't addressed. The total throughput of the hub is limited to that of a single link and all links must operate at the same speed.
Collisions reduce throughput by their very nature. In the worst case, when there are lots of hosts with long cables that attempt to transmit many short frames, excessive collisions can reduce throughput dramatically. However, a Xerox report in 1980 summarized the results of having 20 fast nodes attempting to transmit packets of various sizes as quickly as possible on the same Ethernet segment. Xerox Corporation ( (name ˈziːrɒks is a global document management company which manufactures and sells a range of color and black-and-white printers, multifunction  The results showed that, even for the smallest Ethernet frames (64B), 90% throughput on the LAN was the norm. This is in comparison 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. In Telecommunication, token passing is a Channel access method where a signal called a token is passed around between nodes that authorizes the node to
This report was wildly controversial, as modeling showed that collision-based networks became unstable under loads as low as 40% of nominal capacity. Many early researchers failed to understand the subtleties of the CSMA/CD protocol and how important it was to get the details right, and were really modeling somewhat different networks (usually not as good as real Ethernet). 
While repeaters could isolate some aspects of Ethernet segments, such as cable breakages, they still forwarded all traffic to all Ethernet devices. A network segment is a portion of a Computer network wherein every device communicates using the same Physical layer. This created practical limits on how many machines could communicate on an Ethernet network. Also as the entire network was one collision domain and all hosts had to be able to detect collisions anywhere on the network the number of repeaters between the farthest nodes was limited. Finally segments joined by repeaters had to all operate at the same speed, making phased-in upgrades impossible.
To alleviate these problems, bridging was created to communicate at the data link layer while isolating the physical layer. With bridging, only well-formed packets are forwarded from one Ethernet segment to another; collisions and packet errors are isolated. Bridges learn where devices are, by watching MAC addresses, and do not forward packets across segments when they know the destination address is not located in that direction. In Computer networking a Media Access Control address ( MAC address) or Ethernet Hardware Address ( EHA) hardware address
Prior to discovery of network devices on the different segments, Ethernet bridges and switches work somewhat like Ethernet hubs, passing all traffic between segments. However, as the switch discovers the addresses associated with each port, it only forwards network traffic to the necessary segments improving overall performance. Broadcast traffic is still forwarded to all network segments. In Computer networking, broadcasting refers to transmitting a packet that will be received (conceptually by every device on the network Bridges also overcame the limits on total segments between two hosts and allowed the mixing of speeds, both of which became very important with the introduction of Fast Ethernet. In Computer networking Fast Ethernet is a collective term for a number of Ethernet standards that carry traffic at the nominal rate of 100 Mbit/s against the original
Early bridges examined each packet one by one using software on a CPU, and some of them were significantly slower than hubs (multi-port repeaters) at forwarding traffic, especially when handling many ports at the same time. In 1989 the networking company Kalpana introduced their EtherSwitch, the first Ethernet switch. Kalpana was a Computer networking equipment manufacturer located in Silicon Valley during the 1980s and 1990s Kalpana introduced the concept An Ethernet switch does bridging in hardware, allowing it to forward packets at full wire speed. It is important to remember that the term switch was invented by device manufacturers and does not appear in the 802. 3 standard. Functionally, the two terms are interchangeable.
Since packets are typically only delivered to the port they are intended for, traffic on a switched Ethernet is slightly 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. Address Resolution Protocol (ARP spoofing, also known as ARP poisoning or ARP Poison Routing (APR is a technique used to attack an Ethernet wired In Computer networking, MAC flooding is a technique employed to compromise the security of Network switches Switches maintain a list (called a CAM (Content The bandwidth advantages, the slightly better 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.
When a twisted pair or fiber link segment is used and neither end is connected to a hub, full-duplex Ethernet becomes possible over that segment. A duplex Communication system is a system composed of two connected parties or devices which can communicate with one another in both directions In full duplex mode both devices can transmit and receive to/from each other at the same time, and there is no collision domain. This doubles the aggregate bandwidth of the link and is sometimes advertised as double the link speed (e. g. 200 Mbit/s) to account for this. However, this is misleading as performance will only double if traffic patterns are symmetrical (which in reality they rarely are). The elimination of the collision domain also means that all the link's bandwidth can be used and that segment length is not limited by the need for correct collision detection (this is most significant with some of the fiber variants of Ethernet).
In the early days of Fast Ethernet, Ethernet switches were relatively expensive devices. In Computer networking Fast Ethernet is a collective term for a number of Ethernet standards that carry traffic at the nominal rate of 100 Mbit/s against the original However, hubs suffered from the problem that if there were any 10BASE-T devices connected then the whole system would have to run at 10 Mbit. Therefore a compromise between a hub and a switch appeared known as a dual speed hub. These devices consisted of an internal two-port switch, dividing the 10BASE-T (10 Mbit) and 100BASE-T (100 Mbit) segments. A megabit is a unit of Information or computer storage abbreviated Mbit (or Mb) A megabit is a unit of Information or computer storage abbreviated Mbit (or Mb) The device would typically consist of more than two physical ports. When a network device becomes active on any of the physical ports, the device attaches it to either the 10BASE-T segment or the 100BASE-T segment, as appropriate. This prevented the need for an all-or-nothing migration from 10BASE-T to 100BASE-T networks. These devices are also known as dual-speed hubs because the traffic between devices connected at the same speed is not switched.
Simple switched Ethernet networks, while an improvement over hub based Ethernet, suffer from a number of issues:
Some switches offer a variety of tools to combat these issues including:
The autonegotiation standard does not allow autodetection to detect the duplex setting if the other computer is not also set to Autonegotation. Autonegotiation (formerly NWay) is an Ethernet procedure by which two connected devices choose common transmission parameters such as speed and duplex mode In Ethernet, a duplex mismatch is a condition where two connected devices operate in different duplex modes, that is one operates in half duplex while the other When two interfaces are connected and set to different "duplex" modes, the effect of the duplex mismatch is a network that works, but much slower than at its nominal speed. The primary rule for avoiding this is that you must not set one end of a connection to a forced full duplex setting and the other end to autonegotiation.
Many different modes of operations (10BASE-T half duplex, 10BASE-T full duplex, 100BASE-TX half duplex, …) exist for Ethernet over twisted pair cable using 8P8C modular connectors (not to be confused with FCC's RJ45), and most devices are capable of different modes of operations. There are a few standards for Ethernet over twisted pair or Copper -based computer networking physical connectivity methods Modular connector is the name given to a family of Electrical connectors examples of which are pictured A registered jack ( RJ) is a standardized physical interface — both jack construction and wiring pattern — for connecting telecommunications equipment (commonly a Telephone In 1995, a standard was released for allowing two network interfaces connected to each other to autonegotiate the best possible shared mode of operation. This works well for the case of every device being set to autonegotiate. The autonegotiation standard contained a mechanism for detecting the speed but not the duplex setting of Ethernet peers that did not use autonegotiation.
Interoperability problems lead network administrators to manually set the mode of operation of interfaces on network devices. What would happen is that some device would fail to autonegotiate and therefore had to be set into one setting or another. This often led to duplex setting mismatches: in particular, when two interfaces are connected to each other with one set to autonegotiation and one set to full duplex mode, a duplex mismatch results because the autonegotiation process fails and half duplex is assumed – the interface in full duplex mode then transmits at the same time as receiving, and the interface in half duplex mode then gives up on transmitting a packet. A duplex Communication system is a system composed of two connected parties or devices which can communicate with one another in both directions The interface in half duplex mode is not ready to receive a packet, so it signals a collision, and transmissions are halted, for amounts of time based on backoff (random wait times) algorithms. When both packets start trying to transmit again, they interfere again and the backoff strategy may result in a longer and longer wait time before attempting to transmit again; eventually a transmission succeeds but this then causes the flood and collisions to resume.
Because of the wait times, the effect of a duplex mismatch is a network that is not completely 'broken' but is incredibly slow.
The first Ethernet networks, 10BASE5, used thick yellow cable with vampire taps as a shared medium (using CSMA/CD). The Ethernet physical layer is the Physical layer component of the Ethernet standard A vampire tap (also called a piercing tap is a device for physically connecting a station (i Carrier Sense Multiple Access With Collision Detection ( CSMA/CD) in Computer networking is a network control protocol in which a Later, 10BASE2 Ethernet used thinner coaxial cable (with BNC connectors) as the shared CSMA/CD medium. Coaxial cable is a cable consisting of an inner conductor surrounded by a tubular insulating layer typically made from a flexible material with a high Dielectric constant, all The BNC ( Bayonet Neill Concelman) connector is a very common type of RF connector used for terminating Coaxial cable. The later StarLAN 1BASE5 and 10BASE-T used twisted pair connected to Ethernet hubs with 8P8C modular connectors (not to be confused with FCC's RJ45). StarLAN was the first implementation of Ethernet Computer networking on Twisted pair wiring Twisted pair Cabling is a form of wiring in which two conductors (two halves of a single circuit) are wound together for the purposes of canceling out Modular connector is the name given to a family of Electrical connectors examples of which are pictured A registered jack ( RJ) is a standardized physical interface — both jack construction and wiring pattern — for connecting telecommunications equipment (commonly a Telephone
Currently Ethernet has many varieties that vary both in speed and physical medium used. Perhaps the most common forms used are 10BASE-T, 100BASE-TX, and 1000BASE-T. There are a few standards for Ethernet over twisted pair or Copper -based computer networking physical connectivity methods All three utilize twisted pair cables and 8P8C modular connectors (often called RJ45). Modular connector is the name given to a family of Electrical connectors examples of which are pictured A registered jack ( RJ) is a standardized physical interface — both jack construction and wiring pattern — for connecting telecommunications equipment (commonly a Telephone They run at 10 Mbit/s, 100 Mbit/s, and 1 Gbit/s, respectively. However each version has become steadily more selective about the cable it runs on and some installers have avoided 1000BASE-T for everything except short connections to servers.
Fiber optic variants of Ethernet are commonly used in structured cabling applications. An optical fiber (or fibre) is a Glass or Plastic fiber that carries Light along its length Structured cabling is building or campus telecommunications cabling infrastructure that consists of a number of standardized smaller elements (hence structured called subsystems These variants have also seen substantial penetration in enterprise datacenter applications, but are rarely seen connected to end user systems for cost/convenience reasons. A data center is a facility used to house computer systems and associated components such as telecommunications and storage systems Their advantages lie in performance, electrical isolation and distance, up to tens of kilometers with some versions. Fiber versions of a new higher speed almost invariably come out before copper. 10 gigabit Ethernet is becoming more popular in both enterprise and carrier networks, with development starting on 40 Gbit/s  and 100 Gbit/s Ethernet. Metcalfe now believes commercial applications using terabit Ethernet may occur by 2015 though he says existing Ethernet standards may have to be overthrown to reach terabit Ethernet. Robert Melancton Metcalfe (born April 7, 1946 in Brooklyn, New York) is an electrical engineer from the United States who co-invented Ethernet A terabit is a unit of Information or Computer storage, abbreviated Tbit (or Tb) 
A data packet on the wire is called a frame. A frame viewed on the actual physical wire would show Preamble and Start Frame Delimiter, in addition to the other data. These are required by all physical hardware. They are not displayed by packet sniffing software because these bits are removed by the Ethernet adapter before being passed on to the host (in contrast, it is often the device driver which removes the CRC32 (FCS) from the packets seen by the user). A Network card, Network Adapter, LAN Adapter or NIC (network interface card is a piece of Computer hardware designed to allow computers In computing a device driver or software driver is a Computer program allowing higher-level computer programs to interact with a Hardware device A cyclic redundancy check (CRC is a type of function that takes as input a data stream of any length and produces as output a value of a certain space commonly a 32-bit integer
The table below shows the complete Ethernet frame, as transmitted. Note that the bit patterns in the preamble and start of frame delimiter are written as bit strings, with the first bit transmitted on the left (not as byte values, which in Ethernet are transmitted least significant bit first). This notation matches the one used in the IEEE 802. 3 standard.
|Preamble||Start-of-Frame-Delimiter||MAC destination||MAC source||Ethertype/Length||Payload||CRC32||Interframe gap|
|7 octets of 10101010||1 octet of 10101011||6 octets||6 octets||2 octets||46-1500 octets||4 octets||12 octets|
After a frame has been sent transmitters are required to transmit 12 octets of idle characters before transmitting the next frame. In Computer networking a Media Access Control address ( MAC address) or Ethernet Hardware Address ( EHA) hardware address EtherType is a field in the Ethernet networking standard ( Ethernet II framing, specifically A cyclic redundancy check (CRC is a type of function that takes as input a data stream of any length and produces as output a value of a certain space commonly a 32-bit integer Ethernet devices must allow a minimum idle period between transmission of Ethernet frames known as the interframe gap (IFG interframe spacing, or In Computing, an octet is a grouping of eight Bits Octet, with the only exception noted below always refers to an entity having exactly eight For 10M this takes 9600 ns, 100M 960 ns, 1000M 96 ns. A nanosecond ( ns) is one billionth of a second See also times of other orders of magnitude.
10/100M transceiver chips (MII PHY) work with 4-bits (nibble) at a time. The Media Independent Interface ( MII) is a standard interface used to connect a Fast Ethernet (i PHY (often ˈfaɪ "fye" is a common abbreviation for the Physical layer of the OSI model. A nibble (often nybble) is the Computing term for a four- Bit aggregation or half an octet (an octet being an 8-bit Byte Therefore the preamble will be 7 instances of 0101 + 0101, and the Start Frame Delimiter will be 0101 + 1101. 8-bit values are sent low 4-bit and then high 4-bit. 1000M transceiver chips (GMII) work with 8 bits at a time, and 10 Gbit/s (XGMII) PHY works with 32 bits at a time. Gigabit Media Independent Interface (GMII is an interface between the Media Access Control (MAC device and the physical layer ( PHY)
Some implementations use larger jumbo frames. In Computer networking, jumbo frames are Ethernet frames with more than 1500 bytes of payload ( MTU)
There are several types of Ethernet frames:
In addition, Ethernet frames may optionally contain a IEEE 802.1Q tag to identify what VLAN it belongs to and its IEEE 802.1p priority (quality of service). The Subnetwork Access Protocol (SNAP is a mechanism for multiplexing on networks using IEEE 802 IEEE 8021Q (also known as VLAN Tagging was a project in the IEEE 802 standards process to develop a mechanism to allow multiple bridged networks to transparently A virtual LAN, commonly known as a VLAN, is a group of hosts with a common set of requirements that communicate as if they were attached to the Broadcast domain IEEE 8021p is a standard that provides traffic class expediting and dynamic multicast filtering This encapsulation is defined in the IEEE 802. 3ac specification and increases the maximum frame by 4 bytes to 1522 bytes.
The different frame types have different formats and MTU values, but can coexist on the same physical medium. In Computer networking, the term Maximum Transmission Unit ( MTU) refers to the size (in Bytes of the largest packet or frame
Versions 1. 0 and 2. 0 of the Digital/Intel/Xerox (DIX) Ethernet specification have a 16-bit sub-protocol label field called the EtherType. Digital Equipment Corporation was a pioneering American company in the Computer industry Xerox Corporation ( (name ˈziːrɒks is a global document management company which manufactures and sells a range of color and black-and-white printers, multifunction EtherType is a field in the Ethernet networking standard ( Ethernet II framing, specifically The original IEEE 802.3 Ethernet specification replaced that with a 16-bit length field, with the MAC header followed by an IEEE 802.2 logical link control (LLC) header; the maximum length of a packet was 1500 bytes. IEEE 8023 is a collection of IEEE standards defining the Physical layer, and the media access control (MAC sublayer of the Data link layer, IEEE 8022 is the IEEE 802 standard defining Logical Link Control (LLC which is the upper portion of the data link layer for Local area networks The According to the IEEE 802 family of standards Logical Link Control ( LLC) is the upper sublayer of the OSI Data Link Layer. The two formats were eventually unified by the convention that values of that field between 0 and 1500 indicated the use of the original 802. 3 Ethernet format with a length field, while values of 1536 decimal (0600 hexadecimal) and greater indicated the use of the DIX frame format with an EtherType sub-protocol identifier.  This convention allows software to determine whether a frame is an Ethernet II frame or an IEEE 802. 3 frame, allowing the coexistence of both standards on the same physical medium. See also Jumbo Frames. In Computer networking, jumbo frames are Ethernet frames with more than 1500 bytes of payload ( MTU)
By examining the 802. 2 LLC header, it is possible to determine whether it is followed by a SNAP (subnetwork access protocol) header. The Subnetwork Access Protocol (SNAP is a mechanism for multiplexing on networks using IEEE 802 Some protocols, particularly those designed for the OSI networking stack, operate directly on top of 802. The Open Systems Interconnection (usually abbreviated to OSI) was an effort to standardize networking that was started in 1982 by the International A protocol stack (sometimes communications stack) is a particular software implementation of a Computer networking protocol suite 2 LLC, which provides both datagram and connection-oriented network services. The LLC header includes two additional eight-bit address fields, called service access points or SAPs in OSI terminology; when both source and destination SAP are set to the value 0xAA, the SNAP service is requested. The SNAP header allows EtherType values to be used with all IEEE 802 protocols, as well as supporting private protocol ID spaces. IEEE 802 refers to a family of IEEE standards dealing with Local area networks and Metropolitan area networks More specifically the IEEE 802 standards are In IEEE 802. 3x-1997, the IEEE Ethernet standard was changed to explicitly allow the use of the 16-bit field after the MAC addresses to be used as a length field or a type field.
Novell's "raw" 802. Novell Inc ( is a global Software Corporation based in the United States specializing in enterprise operating systems such as SUSE 3 frame format was based on early IEEE 802. 3 work. Novell used this as a starting point to create the first implementation of its own IPX Network Protocol over Ethernet. Internetwork Packet Exchange ( IPX) is the OSI-model Network layer protocol in the IPX/SPX Protocol stack. They did not use any LLC header but started the IPX packet directly after the length field. This does not conform to the IEEE 802. 3 standard, but since IPX has always FF at the first two bytes (while in IEEE 802. 2 LLC that pattern is theoretically possible but extremely unlikely), in practice this mostly coexists on the wire with other Ethernet implementations, with the notable exception of some early forms of DECnet which got confused by this. DECnet is a suite of Network protocols created by Digital Equipment Corporation, originally released in 1975 in order to connect two PDP-11 Minicomputers
Novell NetWare used this frame type by default until the mid nineties, and since Netware was very widespread back then, while IP was not, at some point in time most of the world's Ethernet traffic ran over "raw" 802. NetWare is a Network operating system developed by Novell Inc 3 carrying IPX. Since Netware 4. 10, Netware now defaults to IEEE 802. 2 with LLC (Netware Frame Type Ethernet_802. 2) when using IPX. (See "Ethernet Framing" in References for details. )
Mac OS uses 802. Mac OS is the trademarked name for a series of Graphical user interface -based Operating systems developed by Apple Inc 2/SNAP framing for the AppleTalk V2 protocol suite on Ethernet ("EtherTalk") and Ethernet II framing for TCP/IP. AppleTalk is a proprietary suite of protocols developed by Apple Inc for networking computers
The 802. 2 variants of Ethernet are not in widespread use on common networks currently, with the exception of large corporate Netware installations that have not yet migrated to Netware over IP. In the past, many corporate networks supported 802. 2 Ethernet to support transparent translating bridges between Ethernet and IEEE 802. 5 Token Ring or FDDI networks. The most common framing type used today is Ethernet Version 2, as it is used by most Internet Protocol-based networks, with its EtherType set to 0x0800 for IPv4 and 0x86DD for IPv6. The Internet Protocol ( IP) is a protocol used for communicating data across a Packet-switched Internetwork using the Internet Protocol EtherType is a field in the Ethernet networking standard ( Ethernet II framing, specifically Internet Protocol version 4 ( IPv4) is the fourth revision in the development of the Internet Protocol (IP and it is the first version of the protocol to be widely Internet Protocol version 6 ( IPv6) is an Internet Layer protocol for packet -switched internetworks.
There exists an Internet standard for encapsulating IP version 4 traffic in IEEE 802.2 frames with LLC/SNAP headers. In Computer network Engineering, an Internet Standard (STD is a Specification, put forward by the Internet Engineering Task Force (IETF for IEEE 8022 is the IEEE 802 standard defining Logical Link Control (LLC which is the upper portion of the data link layer for Local area networks The  It is almost never implemented on Ethernet (although it is used on FDDI and on token ring, IEEE 802.11, and other IEEE 802 networks). Fiber distributed data interface ( FDDI) provides a standard for Data transmission in a Local area network Token ring Local area network (LAN technology is a local area network protocol which resides at the Data link layer IEEE 80211 is a set of standards for wireless local area network (WLAN computer communication developed by the IEEE LAN/MAN Standards Committee ( IEEE 802 IEEE 802 refers to a family of IEEE standards dealing with Local area networks and Metropolitan area networks More specifically the IEEE 802 standards are IP traffic cannot be encapsulated in IEEE 802. 2 LLC frames without SNAP because, although there is an LLC protocol type for IP, there is no LLC protocol type for ARP. In Computer networking the Address Resolution Protocol ( ARP) is the method for finding a host's hardware address when only its Network Layer address is IP Version 6 can also be transmitted over Ethernet using IEEE 802. 2 with LLC/SNAP, but, again, that's almost never used (although LLC/SNAP encapsulation of IPv6 is used on IEEE 802 networks).
The IEEE 802.1Q tag, if present, is placed between the Source Address and the EtherType or Length fields. IEEE 8021Q (also known as VLAN Tagging was a project in the IEEE 802 standards process to develop a mechanism to allow multiple bridged networks to transparently The first two bytes of the tag are the Tag Protocol Identifier (TPID) value of 0x8100. This is located in the same place as the EtherType/Length field in untagged frames, so an EtherType value of 0x8100 means the frame is tagged, and the true EtherType/Length is located after the Q-tag. The TPID is followed by two bytes containing the Tag Control Information (TCI) (the IEEE 802. 1p priority (quality of service) and VLAN id). A virtual LAN, commonly known as a VLAN, is a group of hosts with a common set of requirements that communicate as if they were attached to the Broadcast domain The Q-tag is followed by the rest of the frame, using one of the types described above.
A runt frame is an Ethernet frame that is less than the IEEE 802.3 minimum length of 64 bytes. IEEE 8023 is a collection of IEEE standards defining the Physical layer, and the media access control (MAC sublayer of the Data link layer, Possible causes are: Collision, Underruns, Bad network card or Software.  
The 10 gigabit Ethernet family of standards encompasses media types for single-mode fibre (long haul), multi-mode fibre (up to 300m), copper backplane (up to 1m) and copper twisted pair (up to 100m). It was first standardised as IEEE Std 802. 3ae-2002, IEEE 802.3ae, but is now included in IEEE Std 802. 3-2005.
10 gigabit Ethernet is still an emerging technology, and it remains to be seen which of the standards will gain commercial acceptance.
It has been observed that Ethernet traffic has self-similar properties, with important consequences for traffic engineering. Avionics Full-Duplex Switched Ethernet (AFDX is a deterministic data network for safety critical applications that utilizes dedicated bandwidth while providing Quality of Service A Metro Ethernet is a Computer network based on the Ethernet standard and which covers a Metropolitan area. In Mathematics, a self-similar object is exactly or approximately similar to a part of itself (i