Ethernet over twisted pair
Encyclopedia
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Ethernet over twisted-pair cable (upper) and 8P8C plug (lower) |
Ethernet over twisted pair technologies use twisted-pair cables for the physical layer
Physical layer
The physical layer or layer 1 is the first and lowest layer in the seven-layer OSI model of computer networking. The implementation of this layer is often termed PHY....
of an Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
computer network. Other Ethernet cable standards employ coaxial cable
Coaxial cable
Coaxial cable, or coax, has an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis...
or optical fiber
Optical fiber
An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...
. Early versions developed in the 1980s included StarLAN
StarLAN
StarLAN was the first implementation of 1 megabit per second Ethernet over twisted pair wiring. It was standardized by the standards association of the Institute of Electrical and Electronics Engineers as 802.3e in 1986, as the 1BASE5 version of Ethernet.-Description:StarLAN was developed by AT&T...
followed by 10BASE-T
10BASE-T
Ethernet over twisted pair technologies use twisted-pair cables for the physical layer of an Ethernet computer network. Other Ethernet cable standards employ coaxial cable or optical fiber. Early versions developed in the 1980s included StarLAN followed by 10BASE-T. By the 1990s, fast, inexpensive...
. By the 1990s, fast, inexpensive technologies began to emerge. Currently the most popular are 100BASE-TX (fast Ethernet) and 1000BASE-T (gigabit Ethernet), running at 100 Mbit/s and 1000 Mbit/s (1 Gbit/s), respectively. These standards all use 8P8C connectors.The 8P8C modular connector is often called RJ45 after a telephone industry standard
Registered jack
A registered jack is a standardized physical network interface — both jack construction and wiring pattern — for connecting telecommunications or data equipment to a service provided by a local exchange carrier or long distance carrier. The standard designs for these connectors and their wiring...
. Meanwhile higher-speed implementations generally support lower-speed standards inclusively; thus it is possible to mix different generations of equipment. Inclusive capability is designated 10/100 or 10/100/1000- for connections that support such combinations. The cables usually have four pairs of wires (though 10BASE-T and 100BASE-TX only require two of the pairs). The three standards support both full-duplex and half-duplex communication.
History
The Institute of Electrical and Electronics EngineersInstitute of Electrical and Electronics Engineers
The Institute of Electrical and Electronics Engineers is a non-profit professional association headquartered in New York City that is dedicated to advancing technological innovation and excellence...
(IEEE) standards association
IEEE Standards Association
The Institute of Electrical and Electronics Engineers Standards Association is an organization within IEEE that develops global standards in a broad range of industries, including: power and energy, biomedical and health care, information technology, telecommunication, transportation,...
ratified several versions of the technology.
The first two early designs were StarLAN
StarLAN
StarLAN was the first implementation of 1 megabit per second Ethernet over twisted pair wiring. It was standardized by the standards association of the Institute of Electrical and Electronics Engineers as 802.3e in 1986, as the 1BASE5 version of Ethernet.-Description:StarLAN was developed by AT&T...
, standardized in 1986, at 1 megabit per second,
and LattisNet
LattisNet
LattisNet was a family of computer networking hardware and software products built and sold by SynOptics Communications during the 1980s...
, developed in January 1987, at 10 megabit per second.
Both were developed before the 10BASE-T standard (published in 1990 as IEEE 802.3
IEEE 802.3
IEEE 802.3 is a working group and a collection of IEEE standards produced by the working group defining the physical layer and data link layer's media access control of wired Ethernet. This is generally a local area network technology with some wide area network applications...
i) and both were not compatible with it.
Naming
The common names for the standards derive from aspects of the physical media. The leading number (10 in 10BASE-T) refers to the transmission speed in Mbit/s. BASE denotes that basebandBaseband
In telecommunications and signal processing, baseband is an adjective that describes signals and systems whose range of frequencies is measured from close to 0 hertz to a cut-off frequency, a maximum bandwidth or highest signal frequency; it is sometimes used as a noun for a band of frequencies...
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 several standards for the same transmission speed, they are distinguished by a letter or digit following the T, such as TX.
Cabling
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Twisted-pair Ethernet standards are such that the majority of cables can be wired "straight-through" (pin 1 to pin 1, pin 2 to pin 2 and so on), but others may need to be wired in the "crossover
Ethernet crossover cable
An Ethernet crossover cable is a type of Ethernet cable used to connect computing devices together directly. Normal straight through or patch cables were used to connect from a host network interface controller to a network switch, hub or router.A cable with connections that "cross over" was used...
" form (receive to transmit and transmit to receive).
10BASE-T and 100BASE-TX only require two pairs to operate, located on pins 1 plus 2 and pins 3 plus 6. Since 10BASE-T and 100BASE-TX need only two pairs and Category 5 cable
Category 5 cable
Category 5 cable is a twisted pair cable for carrying signals. This type of cable is used in structured cabling for computer networks such as Ethernet. It is also used to carry other signals such as telephony and video. The cable is commonly connected using punch down blocks and modular connectors...
has four pairs, it is possible, but not standards compliant, to run two network connections or use spare pairs for PoE (Power over Ethernet) (or a network connection and two phone lines) over a Category 5 cable by using the normally unused pairs (pins 4–5, 7–8) in 10- and 100-Mbit/s configurations. In practice, great care must be taken to separate these pairs as most 10/100-Mbit/s hubs, switches and PCs electrically terminate
Electrical termination
Electrical termination of a signal involves providing a terminator at the end of a wire or cable to prevent an RF signal from being reflected back from the end, causing interference...
the unused pins. Moreover, 1000BASE-T requires all four pairs to operate, pins 1 and 2, 3 and 6 — as well as 4 and 5, 7 and 8.
It is conventional to wire cables for 10- or 100-Mbit/s Ethernet to either the T568A or T568B standards. Since these standards differ only in that they swap the positions of the two pairs used for transmitting and receiving (TX/RX), a cable with T568A wiring at one end and T568B wiring at the other is referred to as a crossover cable. The terms used in the explanations of the 568 standards, tip and ring
Tip and ring
"Tip" and "Ring" are common terms in the telephone service industry referring to the two wires or sides of an ordinary telephone line. Tip is the ground side and Ring is the battery side of a phone circuit. In the UK these are referred to as the 'A' and 'B' wires...
, refer to older communication technologies
TRS connector
A TRS connector is a common family of connector typically used for analog signals including audio. It is cylindrical in shape, typically with three contacts, although sometimes with two or four . It is also called an audio jack, phone jack, phone plug, and jack plug...
, and equate to the positive and negative
Electric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...
parts of the connections.
A 10BASE-T or 100BASE-TX node such as a PC, with a connector called medium dependent interface
Medium dependent interface
A medium dependent interface describes the interface in a computer network from a physical layer implementation to the physical medium used to carry the transmission....
s (MDI), transmits
Transmission (telecommunications)
Transmission, in telecommunications, is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless...
on pin 1 and 2 and receives on pin 3 and 6 to a network device
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....
using a "straight-through" cable. In order for two network devices or two nodes to communicate with each other (such as a switch
Network switch
A network switch or switching hub is a computer networking device that connects network segments.The term commonly refers to a multi-port network bridge that processes and routes data at the data link layer of the OSI model...
to another switch or computer to computer) a crossover cable is often required at speeds of 10 or 100 Mbit/s. If available, connections can be made with a straight-through cable by means of an MDI-X port, also known as an "internal crossover" or "embedded crossover" connection. Hub
Ethernet hub
An Ethernet hub, active hub, network hub, repeater hub or hub is a device for connecting multiple Ethernet devices together and making them act as a single network segment. A hub works at the physical layer of the OSI model. The device is a form of multiport repeater...
and switch ports with such internal crossovers are usually labelled as such, with "uplink" or "X". For example, 3Com
3Com
3Com was a pioneering digital electronics manufacturer best known for its computer network infrastructure products. The company was co-founded in 1979 by Robert Metcalfe, Howard Charney, Bruce Borden, and Greg Shaw...
usually labels their ports 1X, 2X, and so on. In some cases a button is provided to allow a port to act as either a normal or an uplink port.
Many modern Ethernet host adapters can automatically detect another computer connected with a straight-through cable and then automatically introduce the required crossover, if needed; if neither of the adapters has this capability, then a crossover cable is required. Most newer switches have automatic crossover ("auto MDI-X" or "auto-uplink") on all ports, eliminating the uplink port and the MDI/MDI-X switch, and allowing all connections to be made with straight-through cables. If both devices being connected support 1000BASE-T according to the standards, they will connect regardless of the cable being used or how it is wired.
A 10BASE-T transmitter sends two differential voltages, +2.5 V or −2.5 V.
100BASE-TX follows the same wiring patterns as 10BASE-T, but is more sensitive to wire quality and length, due to the higher bit rates.
A 100BASE-TX transmitter sends three differential voltages, +1 V, 0 V, or −1 V.
1000BASE-T uses all four pairs bi-directionally and the standard includes auto MDI-X; however, implementation is optional. With the way that 1000BASE-T implements signaling, how the cable is wired is immaterial in actual usage. The standard on copper twisted pair is IEEE 802.3ab for Cat 5e UTP
UTP
UTP may refer to:* Unlisted Trading Privileges - in finance - the statutory basis for, and by extension, an electronic network which carries quotes and trades for the New York-based NASDAQ stock_exchange....
, or 4D-PAM5; four dimensions using PAM (pulse amplitude modulation) with five voltages, −2 V, −1 V, 0 V, +1 V, and +2 V While +2 V to −2 V voltage may appear at the pins of the line driver, the voltage on the cable is nominally +1 V, +0.5 V, 0 V, −0.5 V and −1 V.
100BASE-TX and 1000BASE-T were both designed to require a minimum of Category 5 cable and also specify a maximum cable length of 100 meters. Category 5 cable has since been deprecated and new installations use Category 5e.
Unlike earlier Ethernet standards using broadband
Broadband
The term broadband refers to a telecommunications signal or device of greater bandwidth, in some sense, than another standard or usual signal or device . Different criteria for "broad" have been applied in different contexts and at different times...
and coaxial cable
Coaxial cable
Coaxial cable, or coax, has an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis...
, such as 10BASE5
10BASE5
10BASE5 was the original commercially available variant of Ethernet.For its physical layer it used cable similar to RG-8/U coaxial cable but with extra braided shielding. This is a stiff, diameter cable with an impedance of 50 ohms , a solid center conductor, a foam insulating filler, a shielding...
(thicknet) and 10BASE2
10BASE2
10BASE2 is a variant of Ethernet that uses thin coaxial cable , terminated with BNC connectors...
(thinnet), 10BASE-T does not specify the exact type of wiring to be used, but instead specifies certain characteristics that a cable must meet. This was done in anticipation of using 10BASE-T in existing twisted-pair wiring systems that may not conform to any specified wiring standard. Some of the specified characteristics are attenuation
Attenuation
In physics, attenuation is the gradual loss in intensity of any kind of flux through a medium. For instance, sunlight is attenuated by dark glasses, X-rays are attenuated by lead, and light and sound are attenuated by water.In electrical engineering and telecommunications, attenuation affects the...
, characteristic impedance
Characteristic impedance
The characteristic impedance or surge impedance of a uniform transmission line, usually written Z_0, is the ratio of the amplitudes of a single pair of voltage and current waves propagating along the line in the absence of reflections. The SI unit of characteristic impedance is the ohm...
, timing jitter
Jitter
Jitter is the undesired deviation from true periodicity of an assumed periodic signal in electronics and telecommunications, often in relation to a reference clock source. Jitter may be observed in characteristics such as the frequency of successive pulses, the signal amplitude, or phase of...
, propagation delay
Propagation delay
Propagation delay is a technical term that can have a different meaning depending on the context. It can relate to networking, electronics or physics...
, and several types of noise. Cable testers are widely available to check these parameters to determine if a cable can be used with 10BASE-T. These characteristics are expected to be met by 100 meters of 24-gauge
American wire gauge
American wire gauge , also known as the Brown & Sharpe wire gauge, is a standardized wire gauge system used since 1857 predominantly in the United States and Canada for the diameters of round, solid, nonferrous, electrically conducting wire...
unshielded twisted-pair cable. However, with high quality cabling, cable runs of 150 meters or longer are often obtained and are considered viable by most technicians familiar with the 10BASE-T specification.
Autonegotiation and duplex mismatch
Many different modes of operations (10BASE-Tx half duplex, 10BASE-T full duplex, 100BASE-TX half duplex, ...) exist for Ethernet over twisted pairTwisted pair
Twisted pair cabling is a type of wiring in which two conductors are twisted together for the purposes of canceling out electromagnetic interference from external sources; for instance, electromagnetic radiation from unshielded twisted pair cables, and crosstalk between neighboring pairs...
, and most network adapters are capable of different modes of operation. 1000BASE-T requires autonegotiation to be on in order to operate.
When two linked interfaces are set to different duplex
Duplex (telecommunications)
A duplex communication system is a system composed of two connected parties or devices that can communicate with one another in both directions. The term multiplexing is used when describing communication between more than two parties or devices....
modes, the effect of this duplex mismatch
Duplex mismatch
In Ethernet, a duplex mismatch is a condition where two connected devices operate in different duplex modes, that is, one operates in half duplex while the other one operates in full duplex. The effect of a duplex mismatch is a network that works but is often much slower than its nominal speed...
is a network that functions much more slowly than its nominal speed. Duplex mismatch may be inadvertently caused when an administrator configures an interface to a fixed mode (e.g. 100 Mbit/s full duplex) and fails to configure the remote interface, leaving it set to autonegotiate. Then, when the autonegotiation process fails, half duplex is assumed by the autonegotiating side of the link.
Variants
| Speed [Mbit/s] | Distance [m] | Name | Standard / Year | Description |
|---|---|---|---|---|
| 1 | 100 (nominally) | StarLAN StarLAN StarLAN was the first implementation of 1 megabit per second Ethernet over twisted pair wiring. It was standardized by the standards association of the Institute of Electrical and Electronics Engineers as 802.3e in 1986, as the 1BASE5 version of Ethernet.-Description:StarLAN was developed by AT&T... |
802.3e 1986 | Runs over four wires (two twisted pair Twisted pair Twisted pair cabling is a type of wiring in which two conductors are twisted together for the purposes of canceling out electromagnetic interference from external sources; for instance, electromagnetic radiation from unshielded twisted pair cables, and crosstalk between neighboring pairs... s) on telephone twisted pair or Category 3 Category 3 cable Category 3 cable, commonly known as Cat 3 or station wire, is an unshielded twisted pair cable designed to reliably carry data up to 10 Mbit/s, with a possible bandwidth of 16 MHz... cable. An active hub Ethernet hub An Ethernet hub, active hub, network hub, repeater hub or hub is a device for connecting multiple Ethernet devices together and making them act as a single network segment. A hub works at the physical layer of the OSI model. The device is a form of multiport repeater... sits in the middle and has a port for each node. Manchester code Manchester code In telecommunication and data storage, Manchester code is a line code in which the encoding of each data bit has at least one transition and occupies the same time... d signaling. |
| 10 | 100 (nominally) | LattisNet LattisNet LattisNet was a family of computer networking hardware and software products built and sold by SynOptics Communications during the 1980s... |
(pre) 802.3i 1987 | Runs over AT&T Premises Distribution System (PDS) wiring or four wires (two twisted pair Twisted pair Twisted pair cabling is a type of wiring in which two conductors are twisted together for the purposes of canceling out electromagnetic interference from external sources; for instance, electromagnetic radiation from unshielded twisted pair cables, and crosstalk between neighboring pairs... s) on telephone twisted pair or Category 3 cable Category 3 cable Category 3 cable, commonly known as Cat 3 or station wire, is an unshielded twisted pair cable designed to reliably carry data up to 10 Mbit/s, with a possible bandwidth of 16 MHz... . |
| 10 | 100 (nominally) | 10BASE-T | 802.3i 1990 | Runs over four wires (two twisted pair Twisted pair Twisted pair cabling is a type of wiring in which two conductors are twisted together for the purposes of canceling out electromagnetic interference from external sources; for instance, electromagnetic radiation from unshielded twisted pair cables, and crosstalk between neighboring pairs... s) on a Category 3 Category 3 cable Category 3 cable, commonly known as Cat 3 or station wire, is an unshielded twisted pair cable designed to reliably carry data up to 10 Mbit/s, with a possible bandwidth of 16 MHz... or Category 5 cable Category 5 cable Category 5 cable is a twisted pair cable for carrying signals. This type of cable is used in structured cabling for computer networks such as Ethernet. It is also used to carry other signals such as telephony and video. The cable is commonly connected using punch down blocks and modular connectors... . Star topology with an active hub Ethernet hub An Ethernet hub, active hub, network hub, repeater hub or hub is a device for connecting multiple Ethernet devices together and making them act as a single network segment. A hub works at the physical layer of the OSI model. The device is a form of multiport repeater... or switch sits in the middle and has a port for each node. This is also the configuration used for 100BASE-T and gigabit Ethernet. Manchester code Manchester code In telecommunication and data storage, Manchester code is a line code in which the encoding of each data bit has at least one transition and occupies the same time... d signaling. |
| 100 | 100 | 100BASE-TX | 802.3u 1995 | 4B5B 4B5B In telecommunication, 4B5B is a form of data communications Block Coding. 4B5B maps groups of four bits onto groups of 5 bits, with a minimum density of 1 bits in the output. When NRZI-encoded, the 1 bits provide necessary clock transitions for the receiver. For example, a run of 4 bits such as... MLT-3 coded signaling, CAT5 Category 5 cable Category 5 cable is a twisted pair cable for carrying signals. This type of cable is used in structured cabling for computer networks such as Ethernet. It is also used to carry other signals such as telephony and video. The cable is commonly connected using punch down blocks and modular connectors... copper cabling with two twisted pairs. |
| 1000 | 100 | 1000BASE‑T | 802.3ab 1999 | PAM-5 Pulse-amplitude modulation Pulse-amplitude modulation, acronym PAM, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses.... coded signaling, At least Category 5 cable Category 5 cable Category 5 cable is a twisted pair cable for carrying signals. This type of cable is used in structured cabling for computer networks such as Ethernet. It is also used to carry other signals such as telephony and video. The cable is commonly connected using punch down blocks and modular connectors... , with Category 5e strongly recommended copper cabling with four twisted pairs. Each pair is used in both directions simultaneously. |
| 100 | 10GBASE‑T | 802.3an 2006 | Uses category 6a cable. |
See also
- 25-pair color code25-pair color codeThe 25-pair color code is a color code used to identify individual conductors in a kind of electrical telecommunication wiring for indoor use, known as twisted pair cables . The colors are applied to the insulation that covers each conductor...
- Copper cable certificationCopper cable certificationIn copper twisted pair wire networks, copper cable certification is achieved through a thorough series of tests in accordance with Telecommunications Industry Association or International Organization for Standardization standards. These tests are done using a certification-testing tool, which...
- Ethernet physical layerEthernet physical layerThe Ethernet physical layer is the physical layer component of the Ethernet family of computer network standards.The Ethernet physical layer evolved over a considerable time span and encompasses quite a few physical media interfaces and several magnitudes of speed...
- Ethernet extenderEthernet extenderAn Ethernet extender is any device used to extend an Ethernet or network segment beyond its inherent distance limitation which is approximately for most common forms of twisted pair Ethernet...
- Fast EthernetFast EthernetIn computer networking, Fast Ethernet is a collective term for a number of Ethernet standards that carry traffic at the nominal rate of 100 Mbit/s, against the original Ethernet speed of 10 Mbit/s. Of the fast Ethernet standards 100BASE-TX is by far the most common and is supported by the...
, 100 Mbit/s - IEEE 802.3IEEE 802.3IEEE 802.3 is a working group and a collection of IEEE standards produced by the working group defining the physical layer and data link layer's media access control of wired Ethernet. This is generally a local area network technology with some wide area network applications...
- Network isolatorNetwork isolatorNetwork isolators are installed as part of a copper Ethernet system, as galvanic isolators.Network data continues to be transmitted across an electrically non-conducting barrier, through the applied principle of electromagnetic induction, whereby high frequency AC voltages conveying data are...
- Power over EthernetPower over EthernetPower over Ethernet or PoE technology describes a system to pass electrical power safely, along with data, on Ethernet cabling. The IEEE standard for PoE requires category 5 cable or higher for high power levels, but can operate with category 3 cable for low power levels...
(PoE) - Twisted pairTwisted pairTwisted pair cabling is a type of wiring in which two conductors are twisted together for the purposes of canceling out electromagnetic interference from external sources; for instance, electromagnetic radiation from unshielded twisted pair cables, and crosstalk between neighboring pairs...