Ethernet over twisted-pair technologies use twisted-pair cables for the

physical layer In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer; The layer most closely associated with the physical connection between devices. This layer may be implemented by a PHY chip. The ...

of an

Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 1 ...

computer network. They are a subset of all Ethernet physical layers. Early Ethernet used various grades of

coaxial cable Coaxial cable, or coax (pronounced ) is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric ( insulating material); many coaxial cables also have a p ...

, but in 1984, StarLAN showed the potential of simple unshielded twisted pair. This led to the development of 10BASE-T and its successors

100BASE-TX In computer networking, Fast Ethernet physical layers carry traffic at the nominal rate of 100 Mbit/s. The prior Ethernet speed was 10 Mbit/s. Of the Fast Ethernet physical layers, 100BASE-TX is by far the most common. Fast Ether ...

1000BASE-T In computer networking, Gigabit Ethernet (GbE or 1 GigE) is the term applied to transmitting Ethernet frames at a rate of a gigabit per second. The most popular variant, 1000BASE-T, is defined by the IEEE 802.3ab standard. It came into use ...

and

10GBASE-T 10 Gigabit Ethernet (10GE, 10GbE, or 10 GigE) 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 IEEE 802.3ae-2002 standard. Unlike previous ...

, supporting speeds of 10 and 100

megabit per second In telecommunications, data-transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mu ...

, then 1 and 10 gigabit per second respectively. Two new variants of 10 megabit per second Ethernet over a ''single'' twisted pair, known as 10BASE-T1S and 10BASE-T1L, were standardized in IEEE Std 802.3cg-2019. 10BASE-T1S has its origins in the automotive industry and may be useful in other short-distance applications where substantial electrical noise is present. 10BASE-T1L is a long-distance Ethernet, supporting connections up to 1 km in length. Both of these standards are finding applications implementing the

Internet of things The Internet of things (IoT) describes physical objects (or groups of such objects) with sensors, processing ability, software and other technologies that connect and exchange data with other devices and systems over the Internet or other com ...

. The earlier standards use 8P8C modular connectors, and supported cable standards range from Category 3 to Category 8. These cables typically have four pairs of wires for each connection, although early Ethernet used only two of the pairs. Unlike the earlier -T standards, the -T1 interfaces were designed to operate over a single pair of conductors and introduce the use of two new connectors referred to as IEC 63171-1 and IEC 63171-6.

History

The first two early designs of twisted-pair networking were StarLAN, standardized by the

IEEE Standards Association The Institute of Electrical and Electronics Engineers Standards Association (IEEE SA) is an operating unit within IEEE that develops global standards in a broad range of industries, including: power and energy, artificial intelligence systems, ...

IEEE 802.3 IEEE 802.3 is a working group and a collection standards defining the physical layer and data link layer's media access control (MAC) of wired Ethernet. The standards are produced by the working group of Institute of Electrical and Electronics ...

e in 1986, at one megabit per second, and LattisNet, developed in January 1987, at 10 megabit per second. Both were developed before the 10BASE-T standard (published in 1990 as IEEE 802.3i) and used different signalling, so they were not directly compatible with it. In 1988, AT&T released StarLAN 10, named for working at 10 Mbit/s. The StarLAN 10 signalling was used as the basis of 10BASE-T, with the addition of ''link beat'' to quickly indicate connection status. Using twisted-pair cabling in a

star topology A star network is an implementation of a spoke–hub distribution paradigm in computer networks. In a star network, every host is connected to a central hub. In its simplest form, one central hub acts as a conduit to transmit messages. ...

addressed several weaknesses of the previous Ethernet standards: * Twisted-pair cables were already in use for telephone service and were already present in many office buildings, lowering the overall cost of deployment * The centralized star topology was also already often in use for telephone service cabling, as opposed to the

bus A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a road vehicle that carries significantly more passengers than an average car or van. It is most commonly used in public transport, but is also in use for cha ...

topology required by earlier Ethernet standards * Using point-to-point links was less prone to failure and greatly simplified troubleshooting compared to a shared bus * Exchanging cheap

repeater hub In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. Som ...

s for more advanced switching hubs provided a viable upgrade path * Mixing different speeds in a single network became possible with the arrival of

Fast Ethernet In computer networking, Fast Ethernet physical layers carry traffic at the nominal rate of 100 Mbit/s. The prior Ethernet speed was 10 Mbit/s. Of the Fast Ethernet physical layers, 100BASE-TX is by far the most common. Fast Ethern ...

* Depending on cable grades, subsequent upgrading to

Gigabit Ethernet In computer networking, Gigabit Ethernet (GbE or 1 GigE) is the term applied to transmitting Ethernet frames at a rate of a gigabit per second. The most popular variant, 1000BASE-T, is defined by the IEEE 802.3ab standard. It came into use ...

or faster could be accomplished by replacing the network switches Although 10BASE-T is rarely used as a normal-operation signaling rate today, it is still in wide use with network interface controllers in Wake-on-LAN power-down mode and for special, low-power, low-bandwidth applications. 10BASE-T is still supported on most twisted-pair Ethernet ports with up to

speed.

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

baseband In telecommunications and signal processing, baseband is the range of frequencies occupied by a signal that has not been modulated to higher frequencies. Baseband signals typically originate from transducers, converting some other variable i ...

transmission is used. The ''T'' designates twisted-pair cable. Where there are several standards for the same transmission speed, they are distinguished by a letter or digit following the T, such as ''TX'' or ''T4'', referring to the encoding method and number of lanes.

Cabling

Most Ethernet cables are wired "straight-through" (pin 1 to pin 1, pin 2 to pin 2, and so on). In some instances the "

crossover Crossover may refer to: Entertainment Albums and songs * ''Cross Over'' (Dan Peek album) * ''Crossover'' (Dirty Rotten Imbeciles album), 1987 * ''Crossover'' (Intrigue album) * ''Crossover'' (Hitomi Shimatani album) * ''Crossover'' (Yoshino ...

" form (receive to transmit and transmit to receive) may still be required. Cables for Ethernet may be wired to either the T568A or T568B termination standards at both ends of the cable. Since these standards differ only in that they swap the positions of the two pairs used for transmitting and receiving, a cable with T568A wiring at one end and T568B wiring at the other results in a crossover cable. A 10BASE-T or 100BASE-TX host uses a connector wiring called medium dependent interfaces (MDI), transmitting on pins 1 and 2 and receiving on pins 3 and 6 to a network device. An infrastructure node (a hub or a

switch In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...

) accordingly uses a connector wiring called MDI-X, transmitting on pins 3 and 6 and receiving on pins 1 and 2. These ports are connected using a straight-through cable so each transmitter talks to the receiver on the other end of the cable. Nodes can have two types of ports: MDI (uplink port) or MDI-X (regular port, 'X' for internal crossover). Hubs and switches have regular ports. Routers, servers and end hosts (e.g.

personal computers A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tec ...

) have uplink ports. When two nodes having the same type of ports need to be connected, a crossover cable may be required, especially for older equipment. Connecting nodes having different types of ports (i.e., MDI to MDI-X and vice versa) requires a straight-through cable. Thus connecting an end host to a hub or switch requires a straight-through cable. Some older switches and hubs provided a button to allow a port to act as either a normal (regular) or an uplink port, i.e. using MDI-X or MDI pinout, respectively. 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 auto MDI-X on all ports 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 whether a straight-through or crossover cable is used. A 10BASE-T transmitter sends two differential voltages, +2.5 V or −2.5 V. A 100BASE-TX transmitter sends three differential voltages, +1 V, 0 V, or −1 V. Unlike earlier Ethernet standards using

broadband In telecommunications, broadband is wide bandwidth data transmission which transports multiple signals at a wide range of frequencies and Internet traffic types, that enables messages to be sent simultaneously, used in fast internet connections. ...

and

, such as 10BASE5 (thicknet) and

10BASE2 10BASE2 (also known as cheapernet, thin Ethernet, thinnet, and thinwire) is a variant of Ethernet that uses thin coaxial cable terminated with BNC connectors to build a local area network. During the mid to late 1980s this was the domin ...

(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 did not conform to any specified wiring standard. Some of the specified characteristics are

attenuation In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at var ...

characteristic impedance The characteristic impedance or surge impedance (usually written Z0) of a uniform transmission line is the ratio of the amplitudes of voltage and current of a single wave propagating along the line; that is, a wave travelling in one direction i ...

propagation delay Propagation delay is the time duration taken for a signal to reach its destination. It can relate to networking, electronics or physics. ''Hold time'' is the minimum interval required for the logic level to remain on the input after triggering ed ...

, and several types of

crosstalk In electronics, crosstalk is any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Crosstalk is usually caused by undesired capacitive, i ...

. 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 Gauge ( or ) may refer to: Measurement * Gauge (instrument), any of a variety of measuring instruments * Gauge (firearms) * Wire gauge, a measure of the size of a wire ** American wire gauge, a common measure of nonferrous wire diameter, es ...

unshielded twisted-pair cable. However, with high-quality cabling, reliable cable runs of 150 meters or longer are often achievable and are considered viable by technicians familiar with the 10BASE-T specification. 100BASE-TX follows the same wiring patterns as 10BASE-T, but is more sensitive to wire quality and length, due to the higher

bit rate In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time. The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction ...

s. 1000BASE-T uses all four pairs bi-directionally using hybrid circuits and cancellers. Data is encoded using 4D-PAM5; four dimensions using

pulse-amplitude modulation Pulse-amplitude modulation (PAM) is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. It is an analog pulse modulation scheme in which the amplitudes of a train of carrier pulse ...

(PAM) with five voltages, −2 V, −1 V, 0 V, +1 V, and +2 V. While +2 V to −2 V 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 Category 5 cable (Cat 5) is a twisted pair cable for computer networks. Since 2001, the variant commonly in use is the Category 5e specification (Cat 5e). The cable standard provides performance of up to 100 MHz and is ...

and also specify a maximum cable length of . Category 5 cable has since been deprecated and new installations use Category 5e.

Shared cable

10BASE-T and 100BASE-TX require only two pairs (pins 1–2, 3–6) to operate. Since common Category 5 cable has four pairs, it is possible to use the spare pairs (pins 4–5, 7–8) in 10- and 100-Mbit/s configurations for other purposes. The spare pairs may be used for

power over Ethernet Power over Ethernet, or PoE, describes any of several standards or ad hoc systems that pass electric power along with data on twisted-pair Ethernet cabling. This allows a single cable to provide both data connection and electrical power to ...

(PoE), for two

plain old telephone service Plain old telephone service (POTS), or plain ordinary telephone system, is a retronym for voice-grade telephone service employing analog signal transmission over copper loops. POTS was the standard service offering from telephone companies from 1 ...

(POTS) lines, or for a second 10BASE-T or 100BASE-TX connection. In practice, great care must be taken to separate these pairs as 10/100-Mbit/s Ethernet equipment electrically terminates the unused pins ("Bob Smith Termination"). Shared cable is not an option for Gigabit Ethernet as 1000BASE-T requires all four pairs to operate.

Single-pair

In addition to the more computer-oriented two and four-pair variants, the 10BASE-T1, 100BASE-T1 and 1000BASE-T1 single-pair Ethernet physical layers are intended for industrial and automotive applications or as optional data channels in other interconnect applications. The single pair operates at full duplex and has a maximum reach of (100BASE-T1, 1000BASE-T1 link segment type A) or up to (1000BASE-T1 link segment type B) with up to four in-line connectors. Both physical layers require a balanced twisted pair with an impedance of 100 Ω. The cable must be capable of transmitting 600 MHz for 1000BASE-T1 and 66 MHz for 100BASE-T1. 2.5 Gb/s, 5 Gb/s, and 10 Gb/s over a 15 m single pair is standardized in 802.3ch-2020. As of 2021, the P802.3cy Task Force is examining having 25, 50, 100 Gb/s speeds at lengths up to 11 m. Similar to PoE, Power over Data Lines (PoDL) can provide up to 50 W to a device.

Connectors

* 8P8C modular connector: For stationary uses in controlled environments, from homes to

datacenter A data center (American English) or data centre (British English)See American and British English spelling differences#-re, -er, spelling differences. is a building, a dedicated space within a building, or a group of buildings used to house comp ...

s, this is the dominant connector. Its fragile locking tab otherwise limits its suitability and durability. Bandwidths supporting up to Cat 8 cabling are defined for this connector format. * M12X: This is the

M12 connector IEC metric screw sized connectors is a family of electrical connectors defined by IEC that are named according to their ISO metric screw thread, namely M5, M8 and M12. The number gives their outer screw thread diameter in millimeters as with the ...

designated for Ethernet, standardized as IEC 61076-2-109. It is a 12 mm metal screw that houses 4 shielded pairs of pins. Nominal bandwidth is 500 MHz (Cat 6A). The connector family is used in chemically and mechanically harsh environments such as factory automation and transportation. Its size is similar to the modular connector. * ix Industrial: This connector is designed to be small yet strong. It has 10 pins and a different locking mechanism than the modular connector. Standardized as IEC 61076-3-124, its nominal bandwidth is 500 MHz (Cat 6A). * Single-pair Ethernet defines its own connectors: ** IEC 63171-1 “LC”: This is a 2-pin connector with a similar locking tab to the modular connector, if thicker. ** IEC 63171-6 “industrial”: This standard defines 5 2-pin connectors that differ in their locking mechanisms and one 4-pin connector with dedicated pins for power. The locking mechanisms range from a metal locking tab to M8 and M12 connectors with screw or push-pull locking. The 4-pin connector is only defined with M8 screw locking.

Autonegotiation and duplex

Ethernet over twisted-pair standards up through Gigabit Ethernet define both

full-duplex A duplex communication system is a point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions. Duplex systems are employed in many communications networks, either to allow ...

and

half-duplex A duplex communication system is a point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions. Duplex systems are employed in many communications networks, either to allow ...

communication. However, half-duplex operation for gigabit speed is not supported by any existing hardware. Higher speed standards, 2.5GBASE-T up to 40GBASE-T running at 2.5 to 40 Gbit/s, consequently define only full-duplex point-to-point links which are generally connected by

network switch A network switch (also called switching hub, bridging hub, and, by the IEEE, MAC bridge) is networking hardware that connects devices on a computer network by using packet switching to receive and forward data to the destination device. A ...

es, and do not support the traditional shared-medium

CSMA/CD Carrier-sense multiple access with collision detection (CSMA/CD) is a medium access control (MAC) method used most notably in early Ethernet technology for local area networking. It uses carrier-sensing to defer transmissions until no other stati ...

operation. Many different modes of operations (10BASE-T half-duplex, 10BASE-T full-duplex, 100BASE-TX half-duplex, etc.) exist for Ethernet over

twisted pair Twisted pair cabling is a type of wiring used for communications in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted b ...

, and most

network adapter A network interface controller (NIC, also known as a network interface card, network adapter, LAN adapter or physical network interface, and by similar terms) is a computer hardware component that connects a computer to a computer network. Ear ...

s are capable of different modes of operation.

Autonegotiation Autonegotiation is a signaling mechanism and procedure used by Ethernet over twisted pair by which two connected devices choose common transmission parameters, such as speed, duplex mode, and flow control. In this process, the connected devices ...

is required in order to make a working 1000BASE-T connection. When two linked interfaces are set to different duplex modes, the effect of this

duplex mismatch On an Ethernet connection, 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 l ...

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 auto-negotiation process fails, half-duplex is assumed by the autonegotiating side of the link.

Variants

Notes

References

External links

*
How to create your own Ethernet Cables
{{DEFAULTSORT:Ethernet Over twisted pair Ethernet cables Physical layer protocols Local loop