1.
Vampire tap
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A vampire tap is a device for physically connecting a station, typically a computer, to a network that uses 10BASE5 cabling. The vampire tap usually has an integrated AUI, from this a short multicore cable connects to the card in the station. Vampire taps allow new connections to be made on a physical cable while the cable is in use. This allows administrators to expand bus-topology network sections without interrupting communications, without a vampire tap, the cable has to be cut and connectors have to be attached to both ends. Network tap Insulation-displacement connector, another insulation-piercing system Image of a Vampire Tap
2.
Medium Attachment Unit
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A Medium Attachment Unit is a transceiver which converts signals on an Ethernet cable to and from Attachment Unit Interface signals. On original 10BASE5 Ethernet, the MAU was typically clamped to the Ethernet cable, for backwards compatibility with equipment which still has external AUI interfaces, MAUs are still available with 10BASE2 or 10BASET connections. The following standard, Fast Ethernet introduces division onto Media Access Controller, some early Fast Ethernet hardware had a physical external MII connectors, functionally similar to AUI connector. Objectives of MAU, Provide the physical means for communication between local network data link entities, Provide a communication channel capable of high bandwidth and low bit error ratio performance. Provide for ease of installation and service, MAU Characteristics, Enables coupling the Physical Layer Signalling by way of the AUI to the explicit baseband coaxial transmission system. Supports message traffic at a rate of 10,100. Provides for driving up to 500m of coaxial cable without the use of a repeater. Permits the DTE to test the MAU and the medium itself, supports system configurations using the CSMA/CD access mechanism defined with baseband signaling. Collision detection and Loop-back functions direct transfer through the MAU and it removes equipment from the network whenever it continuously transmits for periods significantly longer than required for a maximum-length packet, indicating a possible problem with the NIC. The signal quality error test detects silent failures in the circuitry, Link integrity functions detects breaks in the wire pairs. Both Signal quality error test and Link integrity functions assist in fault isolation, two modes of operation, Normal mode, The MAU functions as a direct connection between the baseband medium and the DTE. Data output from the DTE is output to the coaxial trunk medium and this mode is the “normal” mode of operation for the intended message traffic between stations. Monitor mode or Isolated mode, The MAU functions as a connection between the baseband medium and the DTE. Data output from the DTE is suppressed and only data on the coaxial trunk medium is input to the DTE and this mode is for observing message traffic. Receive function The ability to receive serial data bit streams over the baseband medium, collision Presence function The ability to detect the presence of two or more stations concurrent transmissions. Monitor function The ability to inhibit the normal transmit data stream to the medium at the time the normal receive function and collision presence function remain operational. Jabber function The ability to interrupt the transmit function and inhibit an abnormally long output data stream. It removes equipment from the network whenever it continuously transmits for periods longer than required for a maximum-length packet
3.
Ethernet
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Ethernet /ˈiːθərnɛt/ is a family of computer networking technologies commonly used in local area networks, metropolitan area networks and wide area networks. It was commercially introduced in 1980 and first standardized in 1983 as IEEE802.3, over time, Ethernet has largely replaced competing wired LAN technologies such as token ring, FDDI and ARCNET. The original 10BASE5 Ethernet uses coaxial cable as a medium, while the newer Ethernet variants use twisted pair. Over the course of its history, Ethernet data transfer rates have increased from the original 2.94 megabits per second to the latest 100 gigabits per second. The Ethernet standards comprise several wiring and signaling variants of the OSI physical layer in use with Ethernet, systems communicating over Ethernet divide a stream of data into shorter pieces called frames. As per the OSI model, Ethernet provides services up to, since its commercial release, Ethernet has retained a good degree of backward compatibility. Features such as the 48-bit MAC address and Ethernet frame format have influenced other networking protocols, the primary alternative for some uses of contemporary LANs is Wi-Fi, a wireless protocol standardized as IEEE802.11. Ethernet was developed at Xerox PARC between 1973 and 1974 and it was inspired by ALOHAnet, which Robert Metcalfe had studied as part of his PhD dissertation. In 1975, Xerox filed a patent application listing Metcalfe, David Boggs, Chuck Thacker, in 1976, after the system was deployed at PARC, Metcalfe and Boggs published a seminal paper. Metcalfe left Xerox in June 1979 to form 3Com and he convinced Digital Equipment Corporation, Intel, and Xerox to work together to promote Ethernet as a standard. The so-called DIX standard, for Digital/Intel/Xerox, specified 10 Mbit/s Ethernet, with 48-bit destination and source addresses and it was published on September 30,1980 as The Ethernet, A Local Area Network. Data Link Layer and Physical Layer Specifications, version 2 was published in November,1982 and defines what has become known as Ethernet II. Formal standardization efforts proceeded at the time and resulted in the publication of IEEE802.3 on June 23,1983. Ethernet initially competed with two largely proprietary systems, Token Ring and Token Bus, in the process, 3Com became a major company. 3Com shipped its first 10 Mbit/s Ethernet 3C100 NIC in March 1981, an Ethernet adapter card for the IBM PC was released in 1982, and, by 1985, 3Com had sold 100,000. Parallel port based Ethernet adapters were produced for a time, with drivers for DOS, by the early 1990s, Ethernet became so prevalent that it was a must-have feature for modern computers, and Ethernet ports began to appear on some PCs and most workstations. This process was sped up with the introduction of 10BASE-T and its relatively small modular connector. Since then, Ethernet technology has evolved to meet new bandwidth, in addition to computers, Ethernet is now used to interconnect appliances and other personal devices
4.
10BASE2
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As of 2011, IEEE802.3 has deprecated this standard for new installations. The name 10BASE2 is derived from several characteristics of the physical medium, the 10 comes from the transmission speed of 10 Mbit/s. The BASE stands for baseband signalling, and the 2 for a maximum segment length approaching 200 m.10 Mbit/s Ethernet uses Manchester coding. A binary zero is indicated by a low to high transition in the middle of the bit period and this allows the clock to be recovered from the signal. However, the additional transitions double the signal bandwidth, 10BASE2 coax cables have a maximum length of 185 metres. The maximum practical number of nodes that can be connected to a 10BASE2 segment is limited to 30 with a distance of 50 cm. In a 10BASE2 network, each stretch of cable is connected to the using a BNC T-connector. The T-connector must be plugged directly into the network adaptor with no cable in between, as is the case with most other high-speed buses, Ethernet segments have to be terminated with a resistor at each end. Each end of the cable has a 50 ohm resistor attached, typically this resistor is built into a male BNC and attached to the last device on the bus. This is most commonly connected directly to the T-connector on a workstation though it not technically have to be. A few devices such as Digitals DEMPR and DESPR have a built-in terminator, if termination is missing, or if there is a break in the cable, the AC signal on the bus is reflected, rather than dissipated, when it reaches the end. This reflected signal is indistinguishable from a collision, so no communication can take place, when wiring a 10BASE2 network, special care has to be taken to ensure that cables are properly connected to all T-connectors, and appropriate terminators are installed. One, and only one, terminator must be connected to ground via a ground wire, bad contacts or shorts are especially difficult to diagnose, though a time-domain reflectometer will find most problems quickly. A failure at any point of the network cabling tends to prevent all communications, for this reason, 10BASE2 networks can be difficult to maintain and were often replaced by 10BASE-T networks, which also provided a good upgrade path to 100BASE-TX. An alternative, more reliable connection was established by the introduction of EAD sockets, there were proprietary wallport/cable systems that claimed to avoid these problems but these never became widespread, possibly due to a lack of standardization. 10BASE2 systems do have a number of advantages over 10BASE-T, no hub is required as with 10BASE-T, so the hardware cost is minimal, and wiring can be particularly easy since only a single wire run is needed, which can be sourced from the nearest computer. These characteristics mean that 10BASE2 is ideal for a network of two or three machines, perhaps in a home where easily concealed wiring may be an advantage. For a larger complex office network, the difficulties of tracing poor connections make it impractical, unfortunately for 10BASE2, by the time multiple home computer networks became common, the format had already been practically superseded
5.
Ethernet over twisted pair
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Ethernet over twisted pair technologies use twisted-pair cables for the physical layer of an Ethernet computer network. Early Ethernet had used various grades of coaxial cable, but in 1984 and this led to the development of 10BASE-T and its successors 100BASE-TX and 1000BASE-T, supporting speeds of 10,100 and 1,000 Mbit/s respectively. All these three standards define both full-duplex and half-duplex communication, however, half-duplex operation for gigabit speed isnt supported by any existing hardware. All these standards use 8P8C connectors, and the cables from Cat3 to Cat8 have four pairs of wires, though 10BASE-T, the Institute of Electrical and Electronics Engineers standards association ratified several versions of the technology. The first two designs were StarLAN, standardized in 1986, at one megabit per second, and LattisNet, developed in January 1987. Both were developed before the 10BASE-T standard and used different signalling, in 1988 AT&T released StarLAN10, named for working at 10 Mbit/s. The StarLAN10 signalling was used as the basis of 10BASE-T, the centralized star topology was a more common approach to cabling than the bus in earlier standards and easier to manage. Using point-to-point links instead of a shared bus greatly simplified troubleshooting and was prone to failure. Exchanging cheap repeater hubs for more advanced switching hubs provided an upgrade path. Mixing different speeds in a single network became possible with the arrival of Fast Ethernet, depending on cable grades, subsequent upgrading to Gigabit Ethernet or faster may be as easy as replacing the network switches. The common names for the standards derive from aspects of the physical media, the leading number refers to the transmission speed in Mbit/s. BASE denotes that baseband transmission is used, the T designates twisted pair cable, where the pair of wires for each signal is twisted together to reduce radio frequency interference and crosstalk between pairs. Where there are standards for the same transmission speed, they are distinguished by a letter or digit following the T, such as TX, referring to the encoding method. Twisted-pair Ethernet standards are such that the majority of cables can be wired straight-through and it is conventional to wire cables for 10- or 100-Mbit/s Ethernet to either the T568A or T568B standards. The terms used in the explanations of the 568 standards, tip and ring, refer to older communication technologies, and equate to the positive and negative parts of the connections. A 10BASE-T or 100BASE-TX node such as a PC uses a connector wiring called medium dependent interfaces, transmitting on pin 1 and 2, an infrastructure node accordingly uses a connector wiring called MDI-X, transmitting on pin 3 and 6 and receiving on pin 1 and 2. These ports are connected using a cable, so each transmitter talks to the receiver on the other side. Nodes can have two types of ports, MDI or MDI-X, hubs and switches have regular ports
6.
Fast Ethernet
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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. Of the Fast Ethernet standards, 100BASE-TX is by far the most common, Fast Ethernet was introduced in 1995 as the IEEE802. 3u standard and remained the fastest version of Ethernet for three years before the introduction of Gigabit Ethernet. The acronym GE/FE is sometimes used for supporting both standards. Fast Ethernet is an extension of the 10-megabit Ethernet standard and it runs on UTP data or optical fiber cable in a star wired bus topology, similar to 10BASE-T where all cables are attached to a hub. Fast Ethernet devices are backward compatible with existing 10BASE-T systems. Fast Ethernet is sometimes referred to as 100BASE-X, where X is a placeholder for the FX, the standard specifies the use of CSMA/CD for media access control. A full-duplex mode is also specified and in all modern networks use Ethernet switches. The 100 in the type designation refers to the transmission speed of 100 Mbit/s. The letter following the dash refers to the medium that carries the signal. A Fast Ethernet adapter can be divided into a media access controller, which deals with the higher-level issues of medium availability. The MAC may be linked to the PHY by a four-bit 25 MHz synchronous parallel interface known as a media-independent interface, in rare cases the MII may be an external connection but is usually a connection between ICs in a network adapter or even within a single IC. The specs are based on the assumption that the interface between MAC and PHY will be a MII but they do not require it. Repeaters may use the MII to connect to multiple PHYs for their different interfaces, the MII fixes the theoretical maximum data bit rate for all versions of Fast Ethernet to 100 Mbit/s. 100BASE-T is any of several Fast Ethernet standards for twisted pair cables, including, 100BASE-TX, 100BASE-T4, the segment length for a 100BASE-T cable is limited to 100 metres. All are or were standards under IEEE802.3, almost all 100BASE-T installations are 100BASE-TX. In the early days of Fast Ethernet, much vendor advertising centered on claims by competing standards that said vendors standards will work better with existing cables than other standards. Thus most networks had to be rewired for 100 Megabit speed whether or not there had supposedly been CAT3 or CAT5 cable runs, 100BASE-TX is the predominant form of Fast Ethernet, and runs over two wire-pairs inside a category 5 or above cable. Like 10BASE-T, the pairs in a standard connection are terminated on pins 1,2,3 and 6
7.
Gigabit Ethernet
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In computer networking, Gigabit Ethernet is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second, as defined by the IEEE802. 3-2008 standard. It came into use beginning in 1999, gradually supplanting Fast Ethernet in wired local networks, the cables and equipment are very similar to previous standards and have been very common and economical since 2010. Ethernet was the result of the research done at Xerox PARC in the early 1970s, Ethernet later evolved into a widely implemented physical and link layer protocol. Fast Ethernet increased speed from 10 to 100 megabits per second, Gigabit Ethernet was the next iteration, increasing the speed to 1000 Mbit/s. The initial standard for Gigabit Ethernet was produced by the IEEE in June 1998 as IEEE802. 3z,802. 3z is commonly referred to as 1000BASE-X, where -X refers to either -CX, -SX, -LX, or -ZX. For the history behind the X see Fast Ethernet, IEEE802. 3ab, ratified in 1999, defines Gigabit Ethernet transmission over unshielded twisted pair category 5, 5e or 6 cabling, and became known as 1000BASE-T. With the ratification of 802. 3ab, Gigabit Ethernet became a desktop technology as organizations could use their existing copper cabling infrastructure, IEEE802. 3ah, ratified in 2004 added two more gigabit fiber standards, 1000BASE-LX10 and 1000BASE-BX10. This was part of a group of protocols known as Ethernet in the First Mile. Initially, Gigabit Ethernet was deployed in high-capacity backbone network links, in 2000, Apples Power Mac G4 and PowerBook G4 were the first mass-produced personal computers featuring the 1000BASE-T connection. It quickly became a feature in many other computers. There are five physical layer standards for Gigabit Ethernet using optical fiber, twisted pair cable and these standards use 8b/10b encoding, which inflates the line rate by 25%, from 1000 Mbit/s to 1250 Mbit/s, to ensure a DC balanced signal. The symbols are sent using NRZ. Optical fiber transceivers are most often implemented as modules in SFP form or GBIC on older devices. IEEE802. 3ab, which defines the widely used 1000BASE-T interface type, uses a different encoding scheme in order to keep the rate as low as possible. IEEE802. 3ap defines Ethernet Operation over Electrical Backplanes at different speeds, Ethernet in the First Mile later added 1000BASE-LX10 and -BX10. 1000BASE-CX is a standard for Gigabit Ethernet connections with maximum distances of 25 meters using balanced shielded twisted pair. The short segment length is due to high signal transmission rate. 1000BASE-KX is part of the IEEE802. 3ap standard for Ethernet Operation over Electrical Backplanes and this standard defines one to four lanes of backplane links, one RX and one TX differential pair per lane, at link bandwidth ranging from 100Mbit to 10Gbit per second
8.
Baseband
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Baseband is a signal that has a very narrow and near-zero frequency range, i. e. a spectral magnitude that is nonzero only for frequencies in the vicinity of the origin and negligible elsewhere. In telecommunications and signal processing, baseband signals are transmitted without modulation, baseband has a low-frequency—contained within the bandwidth frequency close to 0 hertz up to a higher cut-off frequency. Baseband can be synonymous with lowpass or non-modulated, and is differentiated from passband, bandpass, carrier-modulated, intermediate frequency, or radio frequency. A baseband bandwidth is equal to the highest frequency of a signal or system, or a bound on such frequencies. By contrast, passband bandwidth is the difference between a highest frequency and a nonzero lowest frequency, a baseband channel or lowpass channel is a communication channel that can transfer frequencies that are very near zero. Examples are serial cables and local networks, as opposed to passband channels such as radio frequency channels. Frequency division multiplexing allows an analog telephone wire to carry a telephone call. Passband transmission makes communication possible over a bandpass filtered channel, such as the telephone network local-loop or a wireless channel. The word BASE in Ethernet physical layer standards, for example 10BASE5, 100BASE-TX and 1000BASE-SX, a baseband processor also known as BP or BBP is used to process the down-converted digital signal to retrieve essential data for the wireless digital system. The baseband processing block in receivers is usually responsible for providing data, code pseudo-ranges and carrier phase measurements. A baseband signal or lowpass signal is a signal that can include frequencies that are very near zero, the equivalent baseband signal is Z = I + j Q where I is the inphase signal, Q the quadrature phase signal, and j the imaginary unit. In a digital method, the I and Q signals of each modulation symbol are evident from the constellation diagram. The frequency spectrum of this includes negative as well as positive frequencies. The physical passband signal corresponds to I cos − Q sin = R e where ω is the angular frequency in rad/s. A signal at baseband is often used to modulate a higher frequency signal in order that it may be transmitted via radio. Modulation results in shifting the signal up to higher frequencies than it originally spanned. A key consequence of the usual double-sideband amplitude modulation is that the range of frequencies the signal spans is doubled, thus, the RF bandwidth of a signal is twice its baseband bandwidth. Steps may be taken to reduce this effect, such as single-sideband modulation, some transmission schemes such as frequency modulation use even more bandwidth
9.
Ethernet physical layer
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The Ethernet physical layer evolved over a considerable time span and encompasses quite a few physical media interfaces and several magnitudes of speed. The speed ranges from 1 Mbit/s to 100 Gbit/s, while the medium can range from bulky coaxial cable to twisted pair. In general, network protocol stack software will work similarly on all physical layers,10 Gigabit Ethernet was already used in both enterprise and carrier networks by 2007, with 40 Gbit/s and 100 Gigabit Ethernet ratified. Robert Metcalfe, one of the co-inventors of Ethernet, in 2008 said he believed commercial applications using Terabit Ethernet may occur by 2015, though it might require new Ethernet standards. Many Ethernet adapters and switch ports support multiple speeds, using autonegotiation to set the speed, while this can practically be taken for granted for ports supporting twisted-pair cabling, only few optical-fiber ports support multiple speeds. If auto-negotiation fails, some multiple-speed devices sense the speed used by their partner, a 10/100 Ethernet port supports 10BASE-T and 100BASE-TX. A 10/100/1000 Ethernet port supports 10BASE-T, 100BASE-TX, and 1000BASE-T, generally, layers are named by their specifications,10,100,1000, 10G. – the nominal, usable speed for the MAC layer, encoded PHY sublayers usually run higher bitrates BASE, BROAD, PASS – indicates baseband, broadband, or passband signaling -T, -S, -L, -C, -K. g. X for 8b/10b block encoding, R for large blocks 1,2,4,10 – number of lanes used per link or reach for WAN PHYs For 10 Mbit/s, most twisted pair layers use unique encoding, so most often just -T is used. The following sections provide a summary of official Ethernet media types. In addition to 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 the signal was self-clocking, all Fast Ethernet variants use a star topology. All Gigabit Ethernet variants use a star topology, initially, half-duplex mode was included in the standard but has been abandoned since. Very few devices support gigabit speed in half-duplex,2. 5GBASE-T and 5GBASE-T are scaled-down variants of 10GBASE-T. These physical layers support twisted pair copper cabling only,10 Gigabit Ethernet defines a version of Ethernet with a nominal data rate of 10 Gbit/s, ten times as fast as Gigabit Ethernet. In 2002, the first 10 Gigabit Ethernet standard was published as IEEE Std 802. 3ae-2002, subsequent standards encompass media types for single-mode fibre, multi-mode fibre, copper backplane and copper twisted pair. All 10-gigabit standards were consolidated into IEEE Std 802. 3-2008, as of 2009,10 Gigabit Ethernet is predominantly deployed in carrier networks, where 10GBASE-LR and 10GBASE-ER enjoy significant market shares. Single-lane 25-gigabit Ethernet is based on one 25.78125 GBd lane of the four from the 100 Gigabit Ethernet standard developed by task force P802. 3by, 25GBASE-T over twisted pair was approved alongside 40GBASE-T within IEEE802. 3bq
10.
Coaxial cable
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Coaxial cable, or coax, is a type of cable that has an inner conductor surrounded by a tubular insulating layer, surrounded by a tubular conducting shield. Many coaxial cables also have an outer sheath or jacket. The term coaxial comes from the conductor and the outer shield sharing a geometric axis. Coaxial cable was invented by English engineer and mathematician Oliver Heaviside, Coaxial cable is used as a transmission line for radio frequency signals. Its applications include feedlines connecting radio transmitters and receivers with their antennas, computer network connections, digital audio and this allows coaxial cable runs to be installed next to metal objects such as gutters without the power losses that occur in other types of transmission lines. Coaxial cable also provides protection of the signal from external electromagnetic interference, the cable is protected by an outer insulating jacket. Normally, the shield is kept at ground potential and a signal carrying voltage is applied to the center conductor, the advantage of coaxial design is that electric and magnetic fields are restricted to the dielectric with little leakage outside the shield. Conversely, electric and magnetic fields outside the cable are largely kept from interfering with signals inside the cable, larger diameter cables and cables with multiple shields have less leakage. Common applications of coaxial cable include video and CATV distribution, RF and microwave transmission, the characteristic impedance of the cable is determined by the dielectric constant of the inner insulator and the radii of the inner and outer conductors. A controlled cable characteristic impedance is important because the source and load impedance should be matched to ensure maximum power transfer, other important properties of coaxial cable include attenuation as a function of frequency, voltage handling capability, and shield quality. Coaxial cable design choices affect physical size, frequency performance, attenuation, power handling capabilities, flexibility, strength, the inner conductor might be solid or stranded, stranded is more flexible. To get better performance, the inner conductor may be silver-plated. Copper-plated steel wire is used as an inner conductor for cable used in the cable TV industry. The insulator surrounding the conductor may be solid plastic, a foam plastic. The properties of control some electrical properties of the cable. A common choice is a solid polyethylene insulator, used in lower-loss cables, solid Teflon is also used as an insulator. Some coaxial lines use air and have spacers to keep the conductor from touching the shield. Many conventional coaxial cables use braided copper wire forming the shield and this allows the cable to be flexible, but it also means there are gaps in the shield layer, and the inner dimension of the shield varies slightly because the braid cannot be flat
11.
Ohm
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The ohm is the SI derived unit of electrical resistance, named after German physicist Georg Simon Ohm. The definition of the ohm was revised several times, today the definition of the ohm is expressed from the quantum Hall effect. In many cases the resistance of a conductor in ohms is approximately constant within a range of voltages, temperatures. In alternating current circuits, electrical impedance is also measured in ohms, the siemens is the SI derived unit of electric conductance and admittance, also known as the mho, it is the reciprocal of resistance in ohms. The power dissipated by a resistor may be calculated from its resistance, non-linear resistors have a value that may vary depending on the applied voltage. The rapid rise of electrotechnology in the last half of the 19th century created a demand for a rational, coherent, consistent, telegraphers and other early users of electricity in the 19th century needed a practical standard unit of measurement for resistance. Two different methods of establishing a system of units can be chosen. Various artifacts, such as a length of wire or a standard cell, could be specified as producing defined quantities for resistance, voltage. This latter method ensures coherence with the units of energy, defining a unit for resistance that is coherent with units of energy and time in effect also requires defining units for potential and current. Some early definitions of a unit of resistance, for example, the absolute-units system related magnetic and electrostatic quantities to metric base units of mass, time, and length. These units had the advantage of simplifying the equations used in the solution of electromagnetic problems. However, the CGS units turned out to have impractical sizes for practical measurements, various artifact standards were proposed as the definition of the unit of resistance. In 1860 Werner Siemens published a suggestion for a reproducible resistance standard in Poggendorffs Annalen der Physik und Chemie and he proposed a column of pure mercury, of one square millimetre cross section, one metre long, Siemens mercury unit. However, this unit was not coherent with other units, one proposal was to devise a unit based on a mercury column that would be coherent – in effect, adjusting the length to make the resistance one ohm. Not all users of units had the resources to carry out experiments to the required precision. The BAAS in 1861 appointed a committee including Maxwell and Thomson to report upon Standards of Electrical Resistance, in the third report of the committee,1864, the resistance unit is referred to as B. A. unit, or Ohmad. By 1867 the unit is referred to as simply Ohm, the B. A. ohm was intended to be 109 CGS units but owing to an error in calculations the definition was 1. 3% too small. The error was significant for preparation of working standards, on September 21,1881 the Congrès internationale délectriciens defined a practical unit of Ohm for the resistance, based on CGS units, using a mercury column at zero deg
12.
Fluorinated ethylene propylene
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Fluorinated ethylene propylene or FEP is a copolymer of hexafluoropropylene and tetrafluoroethylene. It differs from the PTFE resins in that it is using conventional injection molding. Fluorinated ethylene propylene was invented by DuPont and is sold under the brandname Teflon FEP, other brandnames are Neoflon FEP from Daikin or Dyneon FEP from Dyneon/3M. FEP is very similar in composition to the fluoropolymers PTFE and PFA, FEP and PFA both share PTFEs useful properties of low friction and non-reactivity, but are more easily formable. FEP is softer than PTFE and melts at 260 °C, it is transparent and resistant to sunlight. FEP is produced by polymerization of mixtures of tetrafluoroethylene and hexafluoropropylene. The mixture is biased to compensate for the low reactivity of the propylene component. The process is initiated with peroxydisulfate, which homolyzes to generate sulfate radicals. Because FEP is poorly soluble in almost all solvents, the polymerization is conducted as an emulsion in water, the polymer contains about 5% of the propylene component. Useful comparison tables of PTFE against FEP, PFA and ETFE can be found on DuPonts website, listing the mechanical, thermal, chemical, electrical and vapour properties of each, side by side. Thermally, FEP stands out from PTFE and PFA by having a point of 260 °C, around forty degrees lower than PFA. Electrically, PTFE, FEP and PFA have identical dielectric constants, however, while PFA has a similar dissipation factor to PTFE, FEPs dissipation is around six times that of PFA and EFTE. Mechanically, FEP is slightly more flexible than PTFE, perhaps surprisingly, it does not withstand repetitive folding as well as PTFE. It also features a poorer coefficient of friction, is softer and has a slightly lower tensile strength than PTFE. A noteworthy property of FEP is that it is superior to PTFE in some coating applications involving exposure to detergents. Like PTFE, FEP is mainly used for wiring, e. g. hookup wire, coaxial cable, wiring for computer wires, an illustrative end product is for coaxial cables like RG-316. In manufacturing high-quality composite parts, such as in the aerospace industry, in such applications, the film is called release film and is intended to prevent the curing adhesive polymer from bonding to the metal tooling. Being able to maintain composure in extreme temperatures and resist damage from chemical fuels further makes FEP a suitable choice in the industry
13.
Transceiver
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A transceiver is a device comprising both a transmitter and a receiver that are combined and share common circuitry or a single housing. When no circuitry is common between transmit and receive functions, the device is a transmitter-receiver, the term originated in the early 1920s. Similar devices include transponders, transverters, and repeaters, in radio terminology, a transceiver means a unit which contains both a receiver and a transmitter. From the beginning days of radio the receiver and transmitter were separate units, amateur radio or ham radio operators can build their own equipment and it is now easier to design and build a simple unit containing both of the functions, transmitting and receiving. Almost all modern radio equipment is now a transceiver but there is an active market for pure radio receivers. An example of a transceiver would be a walkie-talkie or a CB radio, on a wired telephone, the handset contains the transmitter and receiver for the audio and in the 20th century was usually wired to the base unit by tinsel wire. The whole unit is referred to as a receiver. On a mobile telephone or other radiotelephone, the unit is a transceiver. A cordless telephone uses an audio and radio transceiver for the handset, if a speakerphone is included in a wired telephone base or in a cordless base station, the base also becomes an audio transceiver in addition to the handset. A modem is similar to a transceiver, in that it sends and receives a signal and it modulates a signal being transmitted and demodulates a signal being received. Transceivers are called Medium Attachment Units in IEEE802.3 documents and were used in 10BASE2. Fiber-optic gigabit,10 Gigabit Ethernet,40 Gigabit Ethernet, and 100 Gigabit Ethernet utilize transceivers known as GBIC, SFP, SFP+, QSFP, XFP, XAUI, CXP, and CFP. 4P4C, de facto standard connector for telephone handsets Duplex, two-Way communications capability Transponder#Optical communications U. S, patent 0,716,136, John Stone Stone, Apparatus for simultaneously transmitting and receiving space telegraph signals 7 MHz SSB transceiver Homebrew HF transceivers
14.
N connector
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The N connector is a threaded, weatherproof, medium-size RF connector used to join coaxial cables. It was one of the first connectors capable of carrying microwave-frequency signals, originally, the connector was designed to carry signals at frequencies up to 1 GHz in military applications, but todays common Type N easily handles frequencies up to 11 GHz. More recent precision enhancements to the design by Julius Botka at Hewlett Packard have pushed this to 18 GHz, the male connector is hand-tightened and has an air gap between the center and outer conductors. The coupling has a 5/8-24 thread, the center coaxial contacts are identical to TNC and BNC connectors. Amphenol suggests tightening to a torque of 15 inch-pounds, while Andrew Corporation suggest 20 inch-pounds for their hex nut variant, the peak power rating of an N connector is determined by voltage breakdown/ionisation of the air near the center pin. The average power rating is determined by overheating of the contact due to resistive insertion loss. Typical makers curves for a new clean connector with a perfect load give limits of ≈5000 W at 20 MHz and this square root frequency derating law is expected from the skin depth decreasing with frequency. At lower frequencies the same maker recommends an upper bound of ≈1000 V RMS, the N connector follows the MIL-STD-348 standard, defined by the US military, and comes in 50 and 75 ohm versions. The 50 ohm version is used in the infrastructure of land mobile, wireless data, paging. The 75 ohm version is used in the infrastructure of cable television systems. Connecting these two different types of connectors to each other can lead to damage, and/or intermittent operation due to the difference in diameter of the center pin. Unfortunately, many type N connectors are not labeled, and it can be difficult to prevent this situation in a mixed impedance environment. The 50 ohm type N connector is favored by enthusiasts who create their own Wireless LAN antenna systems, the Cantenna is one such design. The enthusiasts have settled on using the N connector as a connection for homebrew antennas. By using a cable with an N connector one can easily interchange homebrew antennas,50 Ω N connectors are also commonly used on amateur radio devices operating in UHF bands. A male N-connector can plug into an female SnapN, the HN connector is slightly larger and is designed for high-voltage applications. RF connector SMA connector, SMB connector, SMC connector UHF connector Optical fiber connector ^ N type connectors from Cmpter Electronics
15.
Electrical termination
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Electrical termination is an electrical industry term used to describe the specific point at which a conductive device, such as wire or cable, ends or starts. The conductive device may or may not pass the carried electricity or signal onto another conductive device at this point, a common point of electrical termination is at a terminal block. A wire typically ends, or terminates, at the terminal block, ordinary electrical cables suffice to carry low frequency alternating current, such as mains power, which reverses direction 100 to 120 times per second, and audio signals. However, they cannot be used to carry currents in the frequency range, above about 30 kHz, because the energy tends to radiate off the cable as radio waves. The higher the frequency of waves moving through a given cable or medium. Transmission lines become necessary when the length of the cable is longer than a significant fraction of the transmitted frequencys wavelength, types of transmission line cables include parallel line, and coaxial cable. and these require high frequency signal termination. The terminator is usually placed at the end of a line or daisy chain bus, and is designed to match the AC impedance of the cable and hence minimize signal reflections. Less commonly, a terminator is also placed at the end of the wire or cable. Radio frequency currents tend to reflect from discontinuities in the such as connectors and joints. Secondary reflections can also occur at the start, allowing interference to persist as repeated echoes of old data. These reflections also act as bottlenecks, preventing the signal power from reaching the destination, transmission line cables require impedance matching to carry electromagnetic signals with minimal reflections and power losses. Signal terminators are designed to match the characteristic impedances at both cable ends. Types of transmission line cables include balanced line such as line, and twisted pairs. Passive terminators often consist of a resistor, however significantly reactive loads may require other passive components such as inductors, capacitors. Active terminators consist of a regulator that keeps the voltage used for the terminating resistor at a constant level. Forced Perfect Termination Forced Perfect Termination can be used on single ended buses where diodes remove over, the signal is locked between two actively regulated voltage levels, which results in superior performance over a standard active terminator. All parallel SCSI units use terminators, SCSI is primarily used for storage and backup. Controller area network, commonly known as CAN Bus, uses terminators consisting of a 120 ohm resistor, dummy loads are commonly used in HF to EHF frequency circuits
16.
Attachment Unit Interface
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The Attachment Unit Interface is a physical and logical interface defined in the original IEEE802.3 standard for 10BASE5 Ethernet. In the OSI Model, this serves as the demarcation point between the Physical and Data-Link layers. The physical interface consists 15 pin connection that provides a path between an Ethernet nodes Physical Signalling and the Medium Attachment Unit, sometimes known as a transceiver. An AUI cable may be up to 50 meters long, although frequently the cable is omitted altogether, the electrical AUI connection was still present inside the equipment. By the mid-1990s AUI had all but disappeared as Fast Ethernet became more common, Gigabit Ethernet and 10 Gigabit Ethernet have respectively the GMII and XGMII standards which are equivalent to AUI. A modified form using a connector called the AAUI was introduced on Apple Macintosh computers in 1991. An AUI connector is a DA-15 and it has a sliding clip in place of the thumbscrews normally found on a D-connector to hold two connectors together. This clip permits the MAU and MAC to be attached to one another even when their size. This clip is however found to be awkward and/or unreliable.3 or later
17.
EAD socket
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An EAD socket was a network connection socket used in the early 1990s. Ethernet networking of this period used thin coax or 10BASE2, all devices on a network segment connected to the same electrical section of RG-58 coaxial cable. Intermediate devices were connected via a T piece, the two ends of the segment were terminated with a resistive network terminator. Although these networks were reliable when connected, they were prone to accidental misconnection by non-technical office staff and this was particularly an issue when devices, such as desktop computers, were being added or removed from the network. Although a rare need at this time, the situation was worse for portable laptops. With the obsolescence of 10BASE2 networks, from the mid 1990s, in favour of Ethernet over twisted pair, EAD is an abbreviation for German Ethernet-Anschlussdose. The EAD standard defines wall mounted Ethernet connection outlets that are more reliable than standard BNC T-connectors, EAD outlets have been developed from TAE connectors for telephony applications but they are intended for connecting coaxial network cables like 10BASE2. A different mechanical encoding prevents mix-up with phone plugs, EAD cables are duplex connections replacing two thin-wire cables, the T-connector is integrated into the BNC end. The contacts of an EAD outlet are closed if no connector is plugged in, when a cable is plugged in, the normally closed contacts in the socket are opened so that signals pass through the loop cable. Worn out connectors or outlets can cause the problems that haunted the simpler connectors. Description of the EAD system at itwissen. info
18.
International Standard Book Number
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The International Standard Book Number is a unique numeric commercial book identifier. An ISBN is assigned to each edition and variation of a book, for example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, the method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country. The initial ISBN configuration of recognition was generated in 1967 based upon the 9-digit Standard Book Numbering created in 1966, the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108. Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure, however, this can be rectified later. Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines, the ISBN configuration of recognition was generated in 1967 in the United Kingdom by David Whitaker and in 1968 in the US by Emery Koltay. The 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108, the United Kingdom continued to use the 9-digit SBN code until 1974. The ISO on-line facility only refers back to 1978, an SBN may be converted to an ISBN by prefixing the digit 0. For example, the edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has SBN340013818 -340 indicating the publisher,01381 their serial number. This can be converted to ISBN 0-340-01381-8, the check digit does not need to be re-calculated, since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with Bookland European Article Number EAN-13s. An ISBN is assigned to each edition and variation of a book, for example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, a 13-digit ISBN can be separated into its parts, and when this is done it is customary to separate the parts with hyphens or spaces. Separating the parts of a 10-digit ISBN is also done with either hyphens or spaces, figuring out how to correctly separate a given ISBN number is complicated, because most of the parts do not use a fixed number of digits. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for country or territory regardless of the publication language. Some ISBN registration agencies are based in national libraries or within ministries of culture, in other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded. In Canada, ISBNs are issued at no cost with the purpose of encouraging Canadian culture. In the United Kingdom, United States, and some countries, where the service is provided by non-government-funded organisations. Australia, ISBNs are issued by the library services agency Thorpe-Bowker
19.
Institute of Electrical and Electronics Engineers
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The Institute of Electrical and Electronics Engineers is a professional association with its corporate office in New York City and its operations center in Piscataway, New Jersey. It was formed in 1963 from the amalgamation of the American Institute of Electrical Engineers, today, it is the worlds largest association of technical professionals with more than 400,000 members in chapters around the world. Its objectives are the educational and technical advancement of electrical and electronic engineering, telecommunications, computer engineering, IEEE stands for the Institute of Electrical and Electronics Engineers. The association is chartered under this full legal name, IEEEs membership has long been composed of engineers and scientists. For this reason the organization no longer goes by the name, except on legal business documents. The IEEE is dedicated to advancing technological innovation and excellence and it has about 430,000 members in about 160 countries, slightly less than half of whom reside in the United States. The major interests of the AIEE were wire communications and light, the IRE concerned mostly radio engineering, and was formed from two smaller organizations, the Society of Wireless and Telegraph Engineers and the Wireless Institute. After World War II, the two became increasingly competitive, and in 1961, the leadership of both the IRE and the AIEE resolved to consolidate the two organizations. The two organizations merged as the IEEE on January 1,1963. The IEEE is incorporated under the Not-for-Profit Corporation Law of the state of New York and it was formed in 1963 by the merger of the Institute of Radio Engineers and the American Institute of Electrical Engineers. The IEEE serves as a publisher of scientific journals and organizer of conferences, workshops. IEEE develops and participates in activities such as accreditation of electrical engineering programs in institutes of higher learning. The IEEE logo is a design which illustrates the right hand grip rule embedded in Benjamin Franklins kite. IEEE has a dual complementary regional and technical structure – with organizational units based on geography and it manages a separate organizational unit which recommends policies and implements programs specifically intended to benefit the members, the profession and the public in the United States. The IEEE includes 39 technical Societies, organized around specialized technical fields, the IEEE Standards Association is in charge of the standardization activities of the IEEE. The IEEE History Center became an organization to the Engineering. The new ETHW is an effort by various engineering societies as a formal repository of topic articles, oral histories, first-hand histories, Landmarks + Milestones. The IEEE History Center is annexed to Stevens University Hoboken, NJ, in 2016, the IEEE acquired GlobalSpec, adding the provision of engineering data for a profit to its organizational portfolio
20.
Free On-line Dictionary of Computing
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The Free On-line Dictionary of Computing is an online, searchable, encyclopedic dictionary of computing subjects. It was founded in 1985 by Denis Howe and was hosted by Imperial College London, in May 2015, the site was updated to state that it was no longer supported by Imperial College Department of Computing. Howe has served as the editor-in-chief since the inception, with visitors to the website able to make suggestions for additions or corrections to articles. The dictionary incorporates the text of other resources, such as the Jargon File. Due to its availability under the GNU Free Documentation License, a license, it has in turn been incorporated in whole or part into other free content projects
21.
GNU Free Documentation License
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The GNU Free Documentation License is a copyleft license for free documentation, designed by the Free Software Foundation for the GNU Project. It is similar to the GNU General Public License, giving readers the rights to copy, redistribute, copies may also be sold commercially, but, if produced in larger quantities, the original document or source code must be made available to the works recipient. The GFDL was designed for manuals, textbooks, other reference and instructional materials, however, it can be used for any text-based work, regardless of subject matter. For example, the online encyclopedia Wikipedia uses the GFDL for all of its text. The GFDL was released in form for feedback in September 1999. After revisions, version 1.1 was issued in March 2000, version 1.2 in November 2002, the current state of the license is version 1.3. The first discussion draft of the GNU Free Documentation License version 2 was released on September 26,2006, material licensed under the current version of the license can be used for any purpose, as long as the use meets certain conditions. All previous authors of the work must be attributed, all changes to the work must be logged. All derivative works must be licensed under the same license, the full text of the license, unmodified invariant sections as defined by the author if any, and any other added warranty disclaimers and copyright notices from previous versions must be maintained. Technical measures such as DRM may not be used to control or obstruct distribution or editing of the document, the license explicitly separates any kind of Document from Secondary Sections, which may not be integrated with the Document, but exist as front-matter materials or appendices. Secondary sections can contain information regarding the authors or publishers relationship to the subject matter, if the material is modified, its title has to be changed. The license also has provisions for the handling of front-cover and back-cover texts of books, as well as for History, Acknowledgements, Dedications and Endorsements sections. These features were added in part to make the more financially attractive to commercial publishers of software documentation. Endorsements sections are intended to be used in official standard documents, the GFDL requires the ability to copy and distribute the Document in any medium, either commercially or noncommercially and therefore is incompatible with material that excludes commercial re-use. Material that restricts commercial re-use is incompatible with the license and cannot be incorporated into the work, one example of such liberal and commercial fair use is parody. Although the two work on similar copyleft principles, the GFDL is not compatible with the Creative Commons Attribution-ShareAlike license. These exemptions allow a GFDL-based collaborative project with multiple authors to transition to the CC BY-SA3, if it was not originally published on an MMC, it can only be relicensed if it were added to an MMC before November 1,2008. To prevent the clause from being used as a general compatibility measure, at the release of version 1.3, the FSF stated that all content added before November 1,2008 to Wikipedia as an example satisfied the conditions
22.
Local area network
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By contrast, a wide area network, not only covers a larger geographic distance, but also generally involves leased telecommunication circuits or Internet links. An even greater contrast is the Internet, which is a system of globally connected business, Ethernet and Wi-Fi are the two most common transmission technologies in use for local area networks. Historical technologies include ARCNET, Token ring, and AppleTalk, the increasing demand and use of computers in universities and research labs in the late 1960s generated the need to provide high-speed interconnections between computer systems. A1970 report from the Lawrence Radiation Laboratory detailing the growth of their Octopus network gave an indication of the situation. A number of experimental and early commercial LAN technologies were developed in the 1970s, Cambridge Ring was developed at Cambridge University starting in 1974. Ethernet was developed at Xerox PARC in 1973–1975, and filed as U. S, in 1976, after the system was deployed at PARC, Robert Metcalfe and David Boggs published a seminal paper, Ethernet, Distributed Packet-Switching for Local Computer Networks. ARCNET was developed by Datapoint Corporation in 1976 and announced in 1977 and it had the first commercial installation in December 1977 at Chase Manhattan Bank in New York. The initial driving force for networking was generally to share storage and printers, there was much enthusiasm for the concept and for several years, from about 1983 onward, computer industry pundits would regularly declare the coming year to be, “The year of the LAN”. In practice, the concept was marred by proliferation of incompatible physical layer and network protocol implementations, typically, each vendor would have its own type of network card, cabling, protocol, and network operating system. Netware dominated the personal computer LAN business from early after its introduction in 1983 until the mid-1990s when Microsoft introduced Windows NT Advanced Server, of the competitors to NetWare, only Banyan Vines had comparable technical strengths, but Banyan never gained a secure base. During the same period, Unix workstations were using TCP/IP networking, early LAN cabling had generally been based on various grades of coaxial cable. This led to the development of 10BASE-T and structured cabling which is still the basis of most commercial LANs today, while fiber-optic cabling is common for links between switches, use of fiber to the desktop is rare. Many LANs use wireless technologies that are built into Smartphones, tablet computers, in a wireless local area network, users may move unrestricted in the coverage area. Wireless networks have become popular in residences and small businesses, because of their ease of installation, guests are often offered Internet access via a hotspot service. Network topology describes the layout of interconnections between devices and network segments, at the data link layer and physical layer, a wide variety of LAN topologies have been used, including ring, bus, mesh and star. At the higher layers, NetBEUI, IPX/SPX, AppleTalk and others were once common, simple LANs generally consist of cabling and one or more switches. A switch can be connected to a router, cable modem, a LAN can include a wide variety of other network devices such as firewalls, load balancers, and network intrusion detection. LANs can maintain connections with other LANs via leased lines, leased services, depending on how the connections are established and secured, and the distance involved, such linked LANs may also be classified as a metropolitan area network or a wide area network
23.
10 Gigabit Ethernet
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10 Gigabit Ethernet is a group of computer networking technologies for transmitting Ethernet frames at a rate of 10 gigabits per second. It was first defined by the IEEE802. 3ae-2002 standard, half duplex operation and repeater hubs do not exist in 10GbE. Like previous versions of Ethernet, 10GbE can use either copper or fiber cabling, however, because of its bandwidth requirements, higher-grade copper cables are required, category 6a or Class F/Category 7 cables for lengths up to 100 meters. The 10 Gigabit Ethernet standard encompasses a number of different physical layer standards, a networking device, such as a switch or a network interface controller may have different PHY types through pluggable PHY modules, such as those based on SFP+. At the time that the 10 Gigabit Ethernet standard was developed, the WAN PHY encapsulates Ethernet packets in SONET OC-192c frames and operates at a slightly slower data-rate than the local area network PHY. Over the years the Institute of Electrical and Electronics Engineers 802.3 working group has published several standards relating to 10GbE, to implement different 10GbE physical layer standards, many interfaces consist of a standard socket into which different PHY modules may be plugged. Physical layer modules are not specified in a standards body. Relevant MSAs for 10GbE include XENPAK, XFP and SFP+, when choosing a PHY module, a designer considers cost, reach, media type, power consumption, and size. A single point-to-point link can have different MSA pluggable formats on either end as long as the 10GbE optical or copper port type inside the pluggable is identical, XENPAK was the first MSA for 10GE and had the largest form factor. X2 and XPAK were later competing standards with smaller form factors, X2 and XPAK have not been as successful in the market as XENPAK. XFP came after X2 and XPAK and it is also smaller, the newest module standard is the enhanced small form-factor pluggable transceiver, generally called SFP+. Based on the small form-factor pluggable transceiver and developed by the ANSI T11 fibre channel group, it is smaller still, SFP+ has become the most popular socket on 10GE systems. SFP+ modules do only optical to electrical conversion, no clock and data recovery, SFP+ modules share a common physical form factor with legacy SFP modules, allowing higher port density than XFP and the re-use of existing designs for 24 or 48 ports in a 19 rack width blade. Optical modules are connected to a host by either a XAUI, XENPAK, X2, and XPAK modules use XAUI to connect to their hosts. XAUI uses a data channel and is specified in IEEE802.3 Clause 48. XFP modules use a XFI interface and SFP+ modules use an SFI interface, XFI and SFI use a single lane data channel and the 64b/66b encoding specified in IEEE802.3 Clause 49. SFP+ modules can further be grouped into two types of host interfaces, linear or limiting, limiting modules are preferred except when using old fiber infrastructure which requires the use of the linear interface provided by 10GBASE-LRM modules. There are two classifications for optical fiber, single-mode and multi-mode, in SMF light follows a single path through the fiber while in MMF it takes multiple paths resulting in differential mode delay
24.
100 Gigabit Ethernet
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40 Gigabit Ethernet and 100 Gigabit Ethernet are groups of computer networking technologies for transmitting Ethernet frames at rates of 40 and 100 gigabits per second, respectively. The technology was first defined by the IEEE802. 3ba-2010 standard and later by the 802. 3bg-2011,802. 3bj-2014, the standards define numerous port types with different optical and electrical interfaces and different numbers of optical fiber strands per port. Short distances over twinaxial cable are supported, 40GBASE-T uses twisted pair cabling for 40 Gbit/s over up to 30 m. On July 18,2006, a call for interest for a High Speed Study Group to investigate new standards for high speed Ethernet was held at the IEEE802.3 plenary meeting in San Diego. The first 802.3 HSSG study group meeting was held in September 2006, in June 2007, a trade group called Road to 100G was formed after the NXTcomm trade show in Chicago. The project is to provide for the interconnection of equipment satisfying the requirements of the intended applications. The 802. 3ba task force met for the first time in January 2008 and this standard was approved at the June 2010 IEEE Standards Board meeting under the name IEEE Std 802. 3ba-2010. On June 17,2010, the IEEE802. 3ba standard was approved In March 2011 the IEEE802. 3bg standard was approved, on September 10,2011, the P802. 3bj 100 Gbit/s Backplane and Copper Cable task force was approved. The scope of project is to specify additions to and appropriate modifications of IEEE Std 802. On May 10,2013, the P802. 3bm 40 Gbit/s and 100 Gbit/s Fiber Optic Task Force was approved and this project is to specify additions to and appropriate modifications of IEEE Std 802. In addition, to add 40 Gb/s Physical Layer specifications and management parameters for operation on extended reach single-mode fiber optic cables, also on May 10,2013, the P802. 3bq 40GBASE-T Task Force was approved. On June 12,2014, the IEEE802. 3bj standard was approved, on February 16,2015, the IEEE802. 3bm standard was approved. On May 12,2016, the IEEE P802. 3cd Task Force started working to define next generation two-lane 100 Gbit/s PHY, the IEEE802.3 working group is concerned with the maintenance and extension of the Ethernet data communications standard. Additions to the 802.3 standard are performed by forces which are designated by one or two letters. For example, the 802. 3z task force drafted the original Gigabit Ethernet standard,802. 3ba is the designation given to the higher speed Ethernet task force which completed its work to modify the 802.3 standard to support speeds higher than 10 Gbit/s in 2010. The speeds chosen by 802. 3ba were 40 and 100 Gbit/s to support both end-point and link aggregation needs and this was the first time two different Ethernet speeds were specified in a single standard. The decision to include both speeds came from pressure to support the 40 Gbit/s rate for local applications and the 100 Gbit/s rate for internet backbones. The standard was announced in July 2007 and was ratified on June 17,2010, the 40/100 Gigabit Ethernet standards encompass a number of different Ethernet physical layer specifications
25.
Autonegotiation
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Autonegotiation is an Ethernet procedure by which two connected devices choose common transmission parameters, such as speed, duplex mode, and flow control. In this process, the devices first share their capabilities regarding these parameters. In the OSI model, autonegotiation resides in the physical layer, for Ethernet over twisted pair it is defined in clause 28 of IEEE802.3. Autonegotiation was originally defined as an component in the fast Ethernet standard. It is backwards compatible with the normal link pulses used by 10BASE-T, the protocol was significantly extended in the gigabit Ethernet standard, and is mandatory for 1000BASE-T gigabit Ethernet over twisted pair. In 1995, a standard was released to allow connected network adapters to negotiate the best possible shared mode of operation, the initial autonegotiation standard contained a mechanism for detecting the speed but not the duplex setting of Ethernet peers that did not use autonegotiation. Autonegotiation can be used by devices that are capable of different transmission rates, different duplex modes, parallel detection is used when a device that is capable of autonegotiation is connected to one that is not. This happens if the device does not support autonegotiation or autonegotiation is administratively disabled. In this condition, the device that is capable of autonegotiation can determine and this procedure cannot determine the presence of full duplex, so half duplex is always assumed. The standards for 1000BASE-T, 1000BASE-TX and 10GBASE-T require autonegotiation to be always present, other than speed and duplex mode, autonegotiation is used to communicate the port type and the master-slave parameters. Auto-negotiation is based on similar to those used by 10BASE-T devices to detect the presence of a connection to another device. These connection present pulses are sent by Ethernet devices when they are not sending or receiving any frames and they are unipolar positive-only electrical pulses of a nominal duration of 100 ns, with a maximum pulse width of 200 ns, generated at a 16 ms time interval. These pulses are called link integrity test pulses in the 10BASE-T terminology, a device detects the failure of a link if neither a frame nor two of the LIT pulses is received for 50-150 ms. For this scheme to work, devices must send LIT pulses regardless of receiving any, auto-negotiation uses similar pulses labeled as NLP. NLP are still unipolar, positive-only, and of the duration of 100 ns. Each such pulse burst is called a fast link pulse burst, the time interval between the start of each FLP burst is the same 16 milliseconds as between normal link pulses. The FLP burst consists of 17 NLP at a 125 µs time interval, between each pair of two consecutive NLP an additional positive pulse may be present. The presence of this additional pulse indicates a logical 1, its absence a logical 0, as a result, every FLP contains a data word of 16 bits
26.
EtherType
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EtherType is a two-octet field in an Ethernet frame. It is used to indicate which protocol is encapsulated in the payload of the frame, the same field is also used to indicate the size of some Ethernet frames. EtherType was first defined by the Ethernet II framing standard, in modern implementations of Ethernet, the field within the Ethernet frame used to describe the EtherType also can be used to represent the size of the payload of the Ethernet Frame. Historically, depending on the type of Ethernet framing that was in use on an Ethernet segment, Ethernet II framing considered these octets to represent EtherType while the original IEEE802.3 framing considered these octets to represent the size of the payload in bytes. That value was chosen because the length of the data field of an Ethernet 802.3 frame is 1500 bytes. The interpretation of values 1501–1535, inclusive, is undefined, with 802. 1Q VLAN tagging and QinQ the sparse 16-bit EtherType is being completely used. The 16-bit EtherType not only tags the payload class, it serves to help end any VLAN tagging or QinQ stacking. Via look-ahead peeking in streams, the 16-bit EtherType can help to confirm or package a QinQ 32+32+16=80-bit header between the 48-bit MAC addresses and the payload, of those 80-bits only 32-bits are used for dynamic information. For a full 66-bit addressing system,18 bits are needed beyond the MAC, thus, additional EtherType values are required and used for Triple Tagging QinQinQ. Vendor implementations may avoid wasting bandwidth sending those 48-bits in proprietary link compression schemes, the EtherType usually does not contain any CRC or FCS information. The size of the payload of non-standard jumbo frames, typically ~9000 Bytes long, falls within the range used by EtherType, the proposition to resolve this conflict was to substitute the special EtherType value when a length would otherwise be used. However, the proposition was not accepted and it is defunct, the chair of IEEE802.3 at the time, Geoff Thompson, responded to the draft outlining IEEE802. 3s official position and the reasons behind the position. The draft authors also responded to the letter, but no subsequent answer from the IEEE802.3 has been recorded. However, for Ethernet, the Ethernet II header is still used, not all well known de facto uses of EtherTypes are always recorded in the IEEE list of EtherType values. For example, EtherType 0x0806 appears in the IEEE list only as Symbolics, however, the IEEE Registration Authority lists all the accepted EtherTypes, including the 0x0806. IEEE Registration Authority Tutorials IEEE EtherType Registration Authority
27.
Ethernet flow control
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Ethernet flow control is a mechanism for temporarily stopping the transmission of data on Ethernet family computer networks. The first flow control mechanism, the frame, was defined by the IEEE802. 3x standard. The goal of this mechanism is to zero loss under congestion in data center bridging networks. Ethernet is a family of computer network protocols. Flow control can be implemented at the link layer. A sending station may be transmitting data faster than the end of the link can accept it. The first flow control mechanism, the frame, was defined by the Institute of Electrical. The IEEE standard 802. 3x was issued in 1997, an overwhelmed network node can send a pause frame, which halts the transmission of the sender for a specified period of time. A media access control frame is used to carry the pause command, only stations configured for full-duplex operation may send PAUSE frames. The use of a well-known address makes it unnecessary for a station to discover, another advantage of using this multicast address arises from the use of flow control between network switches. The particular multicast address used is selected from a range of address which have been reserved by the IEEE802. 1D standard which specifies the operation of switches used for bridging. Normally, a frame with a multicast destination sent to a switch will be forwarded out to all ports of the switch. However, this range of multicast address is special and will not be forwarded by an 802. 1D-compliant switch, instead, frames sent to this range are understood to be frames meant to be acted upon only within the switch. A pause frame includes the period of time being requested. This number is the duration of the pause. The pause time is measured in units of pause quanta, where each unit is equal to 512 bit times, by 1999, several vendors supported receiving pause frames, but fewer implemented sending them. One original motivation for the frame was to handle network interface controllers that did not have enough buffering to handle full-speed reception. This problem is not as common with advances in bus speeds, a more likely scenario is network congestion within a switch
28.
Ethernet frame
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A data packet on an Ethernet link is called an Ethernet packet, which transports an Ethernet frame as its payload. An Ethernet frame is preceded by a preamble and start frame delimiter, each Ethernet frame starts with an Ethernet header, which contains destination and source MAC addresses as its first two fields. The middle section of the frame is payload data including any headers for other protocols carried in the frame, the frame ends with a frame check sequence, which is a 32-bit cyclic redundancy check used to detect any in-transit corruption of data. A data packet on the wire and the frame as its payload consist of binary data, Ethernet transmits data with the most-significant octet first, within each octet, however, the least-significant bit is transmitted first. The internal structure of an Ethernet frame is specified in IEEE802.3, the table below shows the complete Ethernet packet and the frame inside, as transmitted, for the payload size up to the MTU of 1500 octets. Some implementations of Gigabit Ethernet and other higher-speed variants of Ethernet support larger frames, the optional 802. 1Q tag consumes additional space in the frame. Field sizes for this option are indicated parenthetically in the table above, IEEE802. 1ad allows for multiple tags in each frame. This option is not illustrated here, an Ethernet packet starts with a seven-octet preamble and one-octet start frame delimiter. The preamble consists of a 56-bit pattern of alternating 1 and 0 bits, allowing devices on the network to easily synchronize their receiver clocks and it is followed by the SFD to provide byte-level synchronization and to mark a new incoming frame. The SFD is the value that marks the end of the preamble, which is the first field of an Ethernet packet. The SFD is designed to break the bit pattern of the preamble, the SFD is immediately followed by the destination MAC address, which is the first field in an Ethernet frame. SFD has the value of 171, which is transmitted with least-significant bit first as 213, physical layer transceiver circuitry is required to connect the Ethernet MAC to the physical medium. The connection between a PHY and MAC is independent of the medium and uses a bus from the media independent interface family. Fast Ethernet transceiver chips utilize the MII bus, which is a wide bus, therefore the preamble is represented as 14 instances of 0x5. Gigabit Ethernet transceiver chips use the GMII bus, which is a wide interface. The header features destination and source MAC addresses, the EtherType field and, optionally, the EtherType field is two octets long and it can be used for two different purposes. When used as EtherType, the length of the frame is determined by the location of the interpacket gap, the IEEE802. 1Q tag, if present, is a four-octet field that indicates virtual LAN membership and IEEE802. 1p priority. The minimum payload is 42 octets when an 802. 1Q tag is present and 46 octets when absent, the maximum payload is 1500 octets
29.
Ethernet Alliance
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The Ethernet Alliance was incorporated in the US state of California in August 2005 and officially launched in January 2006 as a non-profit industry consortium to promote and support Ethernet. The Ethernet Alliance work groups are called subcommittees and these subcommittees are focused on efforts around specific standards-based Ethernet initiatives. As of March 2011, the working subcommittees within the Ethernet Alliance included,802. 3av-2009 that extended the speed of EPON networks to 10 Gbit/s. 802. 3an-2006 which defined a specification for running 10 Gigabit Ethernet over twisted-pair copper designated 10GBASE-T, Carrier Ethernet helps guide work being done to support the specific, evolving and growing demands of Ethernet from carriers and service providers. Energy Efficient Ethernet work is based up EEE Standard 802. 3az-2010. Ethernet in the Data Center focus includes protocols such as Data Center Bridging, Fibre Channel over Ethernet, iSCSI, Remote direct memory access over Converged Ethernet, higher Speed Ethernet encompasses all aspects of 40 Gbit/s and 100 Gbit/s Ethernet largely based op the work of IEEE Std. High Speed Modular Interconnects helps drive the adoption through demonstrating interoperability of compliant HS Modular Interconnect devices and ports including optical modules, in previous Ethernet technology iterations, an alliance was formed to support the adoption of that new technology into the market. The Ethernet Alliance was preceded by the Fast Ethernet Alliance, the Gigabit Ethernet Alliance, the 10 Gigabit Ethernet Alliance, and these alliances would dissolve a few years after the completion of the standards effort they supported. Unfortunately, this was long before the technology would reach volume adoption. He worked with others in the industry and the bodies to create an alliance that would exist as long as Ethernet technology existed. The Road to 100G Alliance was formally announced on June 19,2007 at the NXTcomm 2007 show in Chicago, the founding members were Bay Microsystems, Enigma Semiconductor, Integrated Device Technology, IP Infusion, and Lattice Semiconductor. It was headquartered in the Silicon Valley area of California, with the expanded charter and the formation of the HSE and Carrier Ethernet subcommittees, the Road to 100G alliance merged with the Ethernet Alliance on December 31,2008. The Ethernet Alliance offers white papers, presentations, frequently asked questions and these materials are available on the Ethernet Alliance public website and are available free of charge. These papers provide educational materials with an industry-based perspective and they may be based upon the work of Ethernet Alliance subcommittees or support the activities inside Ethernet standards bodies. TEFs offer face-to-face events to bring members of the various Ethernet communities to discuss. The Ethernet Alliance offers an opportunity for academic institutions to become involved in the organization for no fee
