75-516: Emulex Corporation was an American computer hardware company active from 1978 to 2015. The company was a provider of computer network connectivity, monitoring and management hardware and software. The company's I/O connectivity offerings, including its line of Ethernet and Fibre Channel -based connectivity products, are or were used in server and storage products from OEMs, including Cisco , Dell , EMC Corporation , Fujitsu , Hitachi , HP , Huawei , IBM , NetApp , and Oracle Corporation . In 2015,
150-454: 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). 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
225-459: A duplex mismatch . With rare exceptions, a 100BASE-TX port ( 10/100 ) also supports 10BASE-T while a 1000BASE-T port ( 10/100/1000 ) also supports 10BASE-T and 100BASE-TX. Most 10GBASE-T ports also support 1000BASE-T, some even 100BASE-TX or 10BASE-T. While autonegotiation can practically be relied on for Ethernet over twisted pair , few optical-fiber ports support multiple speeds. In any case, even multi-rate fiber interfaces only support
300-417: A signal attenuator if used within a building. 10BASE2 installations, running on RG-58 coaxial cable, require a minimum of 0.5 m between stations tapped into the network cable to minimize reflections. 10BASE-T, 100BASE-T, and 1000BASE-T installations running on twisted pair cable use a star topology . No minimum cable length is required for these networks. Some networking standards are not part of
375-515: A buffer on the switch in its entirety, its frame check sequence verified and only then the packet is forwarded. In modern network equipment, this process is typically done using application-specific integrated circuits allowing packets to be forwarded at wire speed . 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
450-506: 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. Since all communication happens on the same wire, any information sent by one computer is received by all, even if that information
525-499: A departure from both 10BASE-T and 100BASE-TX, 1000BASE-T and above use all four cable pairs for simultaneous transmission in both directions through the use of echo cancellation . Using point-to-point copper cabling provides the opportunity to deliver electrical power along with the data. This is called power over Ethernet and there are several variations defined in IEEE 802.3 standards. Combining 10BASE-T (or 100BASE-TX) with Mode A allows
600-581: 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. 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
675-536: 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
750-748: A hub or a switch to transmit both power and data over only two pairs. This was designed to leave the other two pairs free for analog telephone signals. The pins used in Mode B supply power over the spare pairs not used by 10BASE-T and 100BASE-TX. 4PPoE defined in IEEE 802.3bt can use all four pairs to supply up to 100 W. The cable requirements depend on the transmission speed and the employed encoding method. Generally, faster speeds require both higher-grade cables and more sophisticated encoding. [REDACTED] Some fiber connections have minimum cable lengths due to maximum level constraints on received signals. Fiber ports designed for long-haul wavelengths may require
825-725: A large computer board. One bag also said, " Disk Controllers " while the second bag said, " Communication Controllers ;" the third said " Tape Controllers ." In 1992, Emulex spun off what became QLogic . Much of Emulex's early market was for Digital Equipment Corporation 's VAX and PDP-11 systems. Computer History Museum 's collections include an Emulex disk drive. Headquartered in Costa Mesa, California , Emulex employed more than 1,200 people in 2013. In 2000, Emulex acquired Giganet for $ 645 million, and in 2013, it acquired Endace , based in New Zealand. On April 21, 2009, Broadcom made
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#1733085117560900-464: A link with worse channel parameters can also work but only over a shorter distance. Reach and maximum distance have the same meaning. The following sections provide a brief summary of official Ethernet media types. In addition to these official standards, many vendors have implemented proprietary media types for various reasons—often to support longer distances over fiber optic cabling. Early Ethernet standards used Manchester coding so that
975-541: A loop-free logical topology using the SPB protocol or the older STP on the network switches. 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. Ethernet physical layer The physical-layer specifications of the Ethernet family of computer network standards are published by
1050-553: A practical price point. The Ethernet Technology Consortium proposed an 800 Gbit/s Ethernet PCS variant based on tightly bundled 400GBASE-R in April 2020. In February 2024, the IEEE 802.3df Task Force defined variants for 800 Gbit/s Ethernet over twinaxial copper, electrical backplanes, single-mode and multi-mode optical fiber along with new 200 and 400 Gbit/s variants using 100 Gbit/s lanes. In December 2022, IEEE started
1125-594: A proposal to the Emulex board of directors to buy all existing shares of Emulex for $ 764 million, or $ 9.25 per share, a 40% premium over the stock's closing price on April 20, 2009. After Emulex's board of directors recommended against the sale, Broadcom increased their offer to $ 11 per share on June 30, which valued the company at $ 925 million. On July 9, 2009, it too was rejected Broadcom subsequently withdrew its offer. In February 2015, Avago Technologies Limited announced it would acquire Emulex for $ 8 per share, in cash. Avago,
1200-485: A single wavelength (e.g. 850 nm for 1000BASE-SX or 10GBASE-SR). 10 Gigabit Ethernet was already used in both enterprise and carrier networks by 2007, with 40 Gbit/s and 100 Gigabit Ethernet ratified. In 2017, the fastest additions to the Ethernet family were 200 and 400 Gbit/s . Development of 800 Gbit/s and 1.6 Tbit/s Ethernet standards started in 2021. Generally, layers are named by their specifications: For 10 Mbit/s, no encoding
1275-606: A spinoff of Hewlett Packard, merged with Broadcom in May of that year. Avago assumed the Broadcom name. Ethernet Ethernet ( / ˈ iː θ ər n ɛ t / 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). 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 ,
1350-497: A standard for CSMA/CD based on the IEEE 802 draft. 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. IEEE published the 802.3 standard as a draft in 1983 and as a standard in 1985. Approval of Ethernet on
1425-425: A standard. As part of that process Xerox agreed to relinquish their 'Ethernet' trademark. 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) specified 10 Mbit/s Ethernet, with 48-bit destination and source addresses and a global 16-bit Ethertype -type field. Version 2
1500-430: A standardized reach of up to 80 km. In general, network protocol stack software will work similarly on all physical layers. Many Ethernet adapters and switch ports support multiple speeds by using autonegotiation to set the speed and duplex for the best values supported by both connected devices. If autonegotiation fails, some multiple-speed devices sense the speed used by their partner, but this may result in
1575-401: 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 (1995 IEEE 802.3u Fast Ethernet standard), and is backward compatible with 10BASE-T. The specification was improved in the 1998 release of IEEE 802.3. Autonegotiation
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#17330851175601650-666: Is a version of Ethernet with a nominal data rate of 10 Gbit/s, ten times as fast as Gigabit Ethernet. The first 10 Gigabit Ethernet standard, IEEE Std 802.3ae-2002, was published in 2002. Subsequent standards encompass media types for single-mode fiber (long haul), multi-mode fiber (up to 400 m), copper backplane (up to 1 m) and copper twisted pair (up to 100 m). All 10-gigabit standards were consolidated into IEEE Std 802.3-2008. Most 10-gigabit variants use 64b/66b PCS code ( -R ). 10 Gigabit Ethernet, specifically 10GBASE-LR and 10GBASE-ER , enjoys significant market shares in carrier networks. Single-lane 25-gigabit Ethernet
1725-577: Is based on one 25.78125 GBd lane of the four from the 100 Gigabit Ethernet standard developed by the P802.3by task force. 25GBASE-T over twisted pair was approved alongside 40GBASE-T within IEEE 802.3bq. This class of Ethernet was standardized in June 2010 as IEEE 802.3ba. The work also included the first 100 Gbit/s generation, published in March 2011 as IEEE 802.3bg. A 40 Gbit/s twisted-pair standard
1800-530: Is commonly carried over Ethernet and so it is considered one of the key technologies that make up the Internet . Ethernet was developed at Xerox PARC between 1973 and 1974 as a means to allow Alto computers to communicate with each other. It was inspired by ALOHAnet , which Robert Metcalfe had studied as part of his PhD dissertation and was originally called the Alto Aloha Network. Metcalfe's idea
1875-407: Is either dropped or forwarded to another segment. 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
1950-433: 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. Through the first half of the 1980s, Ethernet's 10BASE5 implementation used
2025-450: Is indicated as all variants use Manchester code . Most twisted pair layers use unique encoding, so most often just -T is used. The reach , especially for optical connections, is defined as the maximum achievable link length that is guaranteed to work when all channel parameters are met ( modal bandwidth , attenuation , insertion losses etc.). With better channel parameters, often a longer, stable link length can be achieved. Vice versa,
2100-476: 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. 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. A collision happens when two stations attempt to transmit at
2175-409: Is mandatory for 1000BASE-T and faster. 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 ,
2250-616: Is now used to interconnect appliances and other personal devices . As Industrial Ethernet it is used in industrial applications and is quickly replacing legacy data transmission systems in the world's telecommunications networks. By 2010, the market for Ethernet equipment amounted to over $ 16 billion per year. In February 1980, the Institute of Electrical and Electronics Engineers (IEEE) started project 802 to standardize local area networks (LAN). The DIX group with Gary Robinson (DEC), Phil Arst (Intel), and Bob Printis (Xerox) submitted
2325-436: Is significantly better. 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,
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2400-412: 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. Despite
2475-518: 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. For signal degradation and timing reasons, coaxial Ethernet segments have a restricted size. Somewhat larger networks can be built by using an Ethernet repeater . Early repeaters had only two ports, allowing, at most,
2550-731: 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 . An implementation of a specific physical layer is commonly referred to as PHY . The Ethernet physical layer has evolved over its existence starting in 1980 and encompasses multiple physical media interfaces and several orders of magnitude of speed from 1 Mbit/s to 400 Gbit/s . The physical medium ranges from bulky coaxial cable to twisted pair and optical fiber with
2625-545: The OSI model , Ethernet provides services up to and including the data link layer . 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
2700-699: The P802.3dj Task Force to define variants for 200, 400, 800 and 1600 Gbit/s over twinaxial copper, electrical backplanes, single-mode and multi-mode optical fiber along with new variants using 100 and 200 Gbit/s lanes. Ethernet in the first mile provides Internet access service directly from providers to homes and small businesses. Starting with Fast Ethernet, the physical layer specifications are divided into three sublayers in order to simplify design and interoperability: Several varieties of Ethernet were specifically designed to run over 4-pair copper structured cabling already installed in many locations. In
2775-573: 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 and broadcast radiation filtering, use VLANs to keep different classes of users separate while using
2850-606: The IEEE 802.3cd task force along with 50 and 200 Gbit/s standards. The third generation using a single 100 Gbit/s lane was standardized in September 2022 as IEEE 802.3ck along with 200 and 400 Gbit/s Ethernet. First generation 200 Gbit/s have been defined by the IEEE 802.3bs task force and standardized in 802.3bs-2017. The IEEE 802.3cd task force has developed 50 and next-generation 100 and 200 Gbit/s standards using one, two, or four 50 Gbit/s lanes respectively. The next generation using 100 Gbit/s lanes
2925-484: The LAN was observed. 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
3000-405: The co-inventors of Ethernet, said he believed commercial applications using Terabit Ethernet may occur by 2015, though it might require new Ethernet standards. It was predicted this would be followed rapidly by a scaling to 100 Terabit, possibly as early as 2020. These were theoretical predictions of technological ability, rather than estimates of when such speeds would actually become available at
3075-427: The company was acquired by Avago Technologies . Emulex was founded in 1978 by Fred B. Cox "as a supplier of data storage products and data communications equipment for the computer industry." By 1983, Emulex was able to advertise its products as if it were grocery items: a 2-page spread headlined "One stop shopping for VAX users? Emulex, of course" showed 3 paper bags, each with the Emulex name and logo and each holding
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3150-621: The course of its history, Ethernet data transfer rates have been increased from the original 2.94 Mbit/s 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
3225-455: 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. An EtherType field in each frame
3300-564: The elimination of the chaining limits inherent in non-switched Ethernet have made switched Ethernet the dominant network technology. 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. Advanced networking features in switches use Shortest Path Bridging (SPB) or
3375-482: 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
3450-449: The evolution of Ethernet technology, all generations of Ethernet (excluding early experimental versions) use the same frame formats. Mixed-speed networks can be built using Ethernet switches and repeaters supporting the desired Ethernet variants. 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
3525-612: 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. 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
3600-504: The group was split into three subgroups, and standardization proceeded separately for each proposal. 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
3675-439: 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 . These evolved into 10BASE-T, which
3750-510: 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. Ethernet has evolved to include higher bandwidth, improved medium access control methods, and different physical media. The multidrop coaxial cable
3825-540: The largest computer networks in the world at that time. An Ethernet adapter card for the IBM PC was released in 1982, and, by 1985, 3Com had sold 100,000. 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
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#17330851175603900-399: 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 . Notably, Ethernet packets have no time-to-live field , leading to possible problems in the presence of
3975-631: 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. Since then, Ethernet technology has evolved to meet new bandwidth and market requirements. In addition to computers, Ethernet
4050-401: The mixing of speeds, both of which are critical to the incremental deployment of faster Ethernet variants. In 1989, Motorola Codex introduced their 6310 EtherSpan, and Kalpana introduced their EtherSwitch; these were examples of the first commercial Ethernet switches. Early switches such as this used cut-through switching where only the header of the incoming packet is examined before it
4125-470: The need for a separate network card. 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, 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
4200-470: The network. 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
4275-577: The now-ubiquitous twisted pair with 10BASE-T. By the end of the 1980s, Ethernet was clearly the dominant network technology. 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. 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
4350-450: 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 . The bandwidth advantages, the improved isolation of devices from each other, the ability to easily mix different speeds of devices and
4425-411: The repeater is limited to that of a single link, and all links must operate at the same speed. 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
4500-549: 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. In 2016, Ethernet replaced InfiniBand as the most popular system interconnect of TOP500 supercomputers. 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 . The first introduction of twisted-pair CSMA/CD
4575-482: 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 (for example, 200 Mbit/s for Fast Ethernet). 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
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#17330851175604650-512: 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
4725-638: The signal was self-clocking and not adversely affected by high-pass filters . All Fast Ethernet variants use a star topology and generally use 4B5B line coding. All Gigabit Ethernet variants use a star topology. 1000BASE-X variants use 8b/10b PCS encoding. Initially, half-duplex mode was included in the standard but has since been abandoned. Very few devices support gigabit speed in half-duplex. 2.5GBASE-T and 5GBASE-T are scaled-down variants of 10GBASE-T and provide longer reach over pre- Cat 6A cabling. These physical layers support twisted-pair copper cabling and backplanes only. 10 Gigabit Ethernet
4800-413: The so-called Blue Book CSMA/CD specification as a candidate for the LAN specification. 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,
4875-411: 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
4950-478: 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. 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
5025-482: The system was deployed at PARC, Metcalfe and Boggs published a seminal paper. Ron Crane , Yogen Dalal , Robert Garner, Hal Murray, Roy Ogus, Dave Redell and John Shoch 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. Metcalfe left Xerox in June 1979 to form 3Com . He convinced Digital Equipment Corporation (DEC), Intel , and Xerox to work together to promote Ethernet as
5100-766: Was StarLAN , standardized as 802.3 1BASE5. 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. 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. In IEEE 802.3,
5175-435: Was derived. 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. Computers are connected to an Attachment Unit Interface (AUI) transceiver , which
5250-446: 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
5325-549: Was essentially to limit the Aloha-like signals inside a cable, instead of broadcasting into the air. 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." In 1975, Xerox filed a patent application listing Metcalfe, David Boggs , Chuck Thacker , and Butler Lampson as inventors. In 1976, after
5400-413: Was published in 2016 as IEEE 802.3bq-2016. The IEEE 802.3cd task force developed 50 Gbit/s along with next-generation 100 and 200 Gbit/s standards using 50 Gbit/s lanes. The first generation of 100 Gigabit Ethernet using 10 and 25 Gbit/s lanes was standardized in June 2010 as IEEE 802.3ba alongside 40 Gigabit Ethernet. The second generation using 50 Gbit/s lanes was developed by
5475-463: Was published in November 1982 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. 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
5550-407: Was replaced with physical point-to-point links connected by Ethernet repeaters or switches . 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. The MAC addresses are used to specify both
5625-561: Was standardized in September 2022 as IEEE 802.3ck along with 100 and 400 Gbit/s PHYs and attachment unit interfaces (AUI) using 100 Gbit/s lanes. An Ethernet standard capable of 200 and 400 Gbit/s is defined in IEEE 802.3bs-2017. 1 Tbit/s may be a further goal. In May 2018, IEEE 802.3 started the 802.3ck task force to develop standards for 100, 200, and 400 Gbit/s PHYs and attachment unit interfaces (AUI) using 100 Gbit/s lanes. The new standards were approved in September 2022. In 2008, Robert Metcalfe , one of
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