Ethernet over twisted pair refers to the use of cables that contain insulated copper wires twisted together in pairs for the
physical layerThe Physical Layer is the first and lowest layer in the seven-layer OSI model of computer networking.The Physical Layer consists of the basic hardware transmission technologies of a network. It is a fundamental layer underlying the logical data structures of the higher level functions in a network...
of an Ethernet network—that is, a network in which the Ethernet protocol provides the data link layer. Other Ethernet cable standards use
coaxial cableCoaxial cable, or coax, is an electrical cable with an inner conductor surrounded by a tubular insulating layer typically of a flexible material with a high dielectric constant, all of which are surrounded by a conductive layer , and finally covered with a thin insulating layer on the outside...
or
optical fiberAn optical fiber is a glass or plastic fiber that carries light along its length. Fiber optics is the overlap of applied science and engineering concerned with the design and application of optical fibers...
.
There are several different standards for this
copperCopper is a chemical element with the symbol Cu and atomic number 29.It is a ductile metal with very high thermal and electrical conductivity. Pure copper is rather soft and malleable and a freshly-exposed surface has a pinkish or peachy color...
-based physical medium. The most widely used are
10BASE-T,
100BASE-TX, and
1000BASE-T (
Gigabit EthernetGigabit Ethernet is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second, as defined by the IEEE 802.3-2008 standard...
), running at 10 Mbit/s, 100 Mbit/s (also Mbps or Mbs
-1), and 1000 Mbit/s (1 Gbit/s) respectively. These three standards all use the same connectors. Higher speed implementations nearly always support the lower speeds as well, so that in most cases different generations of equipment can be freely mixed. They use
8 positionThe 8P8C is a modular connector commonly used to terminate twisted pair and multiconductor flat cable...
modular connectorModular connector is the name given to a family of electrical connectors examples of which are pictured. These connectors were originally used in telephone wiring. Even though they are still used for that purpose they are used for a variety of other things as well. A modular connector's advantage...
s, usually called RJ45 in the context of
EthernetEthernet is a family of frame-based computer networking technologies for local area networks . The name comes from the physical concept of the ether...
over twisted pair. The cables usually used are four-pair twisted pair cable (though 10BASE-T and 10BASE-TX only actually require two of them). Each of the three standards support both full-duplex and half-duplex communication. According to the standards, they all operate over distances of up to 100 meters.
The common names for the standards derive from aspects of the physical media. The
number refers to the theoretical maximum transmission speed in
megabitA megabit is an SI-multiple of the unit of bit for digital information storage or transmission. The International Electrotechnical Commission's standard IEC 60027 specifies the symbol to be Mbit, but Mb is also in common use....
s per second (Mbit/s). The
BASE is short for
basebandIn telecommunications and signal processing, baseband is an adjective that describes signals and systems whose range of frequencies is measured from zero to a maximum bandwidth or highest signal frequency; it is sometimes used as a noun for a band of frequencies starting at zero...
, meaning that there is no
frequency-division multiplexingFrequency-division multiplexing is a form of signal multiplexing which involves assigning non-overlapping frequency ranges to different signals or to each "user" of a medium.-Non telephone:...
(FDM) or other frequency shifting modulation in use; each signal has full control of wire, on a single frequency. The
T designates
twisted 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.-...
cable, where the pair of wires for each signal is twisted together to reduce radio frequency interference and crosstalk between pairs (
FEXTFext is a mythical undead creature in Slavic mythology. Its origins are found in the terrors of the Thirty Years War in central Europe. It is said that the Fext is invincible to bullets, except bullets made of glass. Some of the great generals of that time were supposed to be fexts because of...
and
NEXTNext, Inc. was an American computer company headquartered in Redwood City, California, that developed and manufactured a series of computer workstations intended for the higher education and business markets...
). Where there are several standards for the same transmission speed, they are distinguished by a letter or digit following the T, such as
TX. Some higher-speed standards use
coaxial cableCoaxial cable, or coax, is an electrical cable with an inner conductor surrounded by a tubular insulating layer typically of a flexible material with a high dielectric constant, all of which are surrounded by a conductive layer , and finally covered with a thin insulating layer on the outside...
, designated by
CX.
Cabling
|
TIA/EIA-568-BTIA/EIA-568-B is a set of three telecommunications standards from the Telecommunications Industry Association, a 1988 offshoot of the EIA. The standards address commercial building cabling for telecom products and services. The three standards are formally titled ANSI/TIA/EIA-568-B.1-2001,...
T568A Wiring
| Pin | Pair | Wire | Color |
|---|
| 1 |
3 |
tip |
white/green |
| 2 |
3 |
ring |
green |
| 3 |
2 |
tip |
white/orange |
| 4 |
1 |
ring |
blue |
| 5 |
1 |
tip |
white/blue |
| 6 |
2 |
ring |
orange |
| 7 |
4 |
tip |
white/brown |
| 8 |
4 |
ring |
brown |
|
TIA/EIA-568-BTIA/EIA-568-B is a set of three telecommunications standards from the Telecommunications Industry Association, a 1988 offshoot of the EIA. The standards address commercial building cabling for telecom products and services. The three standards are formally titled ANSI/TIA/EIA-568-B.1-2001,...
T568B Wiring
| Pin | Pair | Wire | Color |
|---|
| 1 |
2 |
tip |
white/orange |
| 2 |
2 |
ring |
orange |
| 3 |
3 |
tip |
white/green |
| 4 |
1 |
ring |
blue |
| 5 |
1 |
tip |
white/blue |
| 6 |
3 |
ring |
green |
| 7 |
4 |
tip |
white/brown |
| 8 |
4 |
ring |
brown |
|
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 "
crossoverAn Ethernet crossover cable is a type of Ethernet cable used to connect computing devices together directly where they would normally be connected via a network switch, hub or router, such as directly connecting two personal computers via their network adapters.- Overview :The 10BASE-T and...
" form (receive to transmit and transmit to receive).
10BASE-T and 100BASE-TX only require two pairs to operate, located on pin 1 + 2, and pin 3 + 6. Since 10BASE-T and 100BASE-TX need only two pairs and
Category 5 cableCategory 5 cable is a twisted pair high signal integrity cable type often referred to as Cat5. Most cables are unshielded relying on the twisted pair design for noise rejection, and some are shielded...
has four pairs, it is possible, but not standards compliant, to run two network connections (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 internally hardwire pins 4–5 together and pins 7–8 together, thereby creating a short-circuit across each "unused" pair. 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" 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 technologiesA TRS connector also called an audio jack, phone plug, jack plug, stereo plug, mini-jack, or mini-stereo, and more recently MP3 jack is a common audio connector...
, and equate to the
positive and negativeElectric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic fields...
parts of the connections.
A 10BASE-T or 100BASE-T node such as a PC also called
MDIA medium dependent interface port or an uplink port is an Ethernet port connection typically used on the Network Interface Card or Integrated NIC port on a PC. Since inputs on a NIC must go to outputs on the router, hub or switch, these latter devices have their inputs and outputs reversed in a...
that
transmitsIn telecommunications, transmission 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 or wireless...
on pin 1 and 2 and receives on pin 3 and 6 to a
network deviceA computer network is a group of interconnected computers. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of some types and categories and also presents the basic components of a network....
uses a "straight-through" cable in the MDI wiring pattern. A straight-through cable is usually used to connect a node to its network device. In order for two network devices or two nodes to communicate with each other (such as a
switchA network switch is a computer networking device that connects network segments.The term commonly refers to a 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.
HubA network hub or repeater hub is a device for connecting multiple twisted pair or fiber optic Ethernet devices together and thus making them act as a single network segment. Hubs work at the physical layer of the OSI model. The device is thus a form of multiport repeater...
and switch ports with such internal crossovers are usually labelled as such, with "uplink" or "X". For example,
3Com3Com is a 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, and is headquartered in Marlborough, Massachusetts...
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.
To connect two computers directly together without a switch, an
Ethernet crossover cableAn Ethernet crossover cable is a type of Ethernet cable used to connect computing devices together directly where they would normally be connected via a network switch, hub or router, such as directly connecting two personal computers via their network adapters.- Overview :The 10BASE-T and...
is often used. Although 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 computers have this capability, then a crossover cable is required. 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.
To connect two hubs or switches directly together, a crossover cable can be used, but some hubs and switches have an uplink port used to connect network devices together, or have a way to manually select MDI or MDI-X on a single port so that a straight-through cable can connect that port to another switch or hub. 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.
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 3 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
UTPUTP may refer to:* uTP - micro Transport Protocol* In music, the second album from singer/songwriter Tori Amos, Under the Pink.* In computer science, unifying theories of programming* The United Tasmania Party...
, 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.
Unlike earlier Ethernet standards using
broadbandThe term broadband can have different meanings in different contexts. The term's meaning has undergone substantial shifts.-In telecommunication:...
and
coaxial cableCoaxial cable, or coax, is an electrical cable with an inner conductor surrounded by a tubular insulating layer typically of a flexible material with a high dielectric constant, all of which are surrounded by a conductive layer , and finally covered with a thin insulating layer on the outside...
, such as
10BASE510BASE5 is the original "full spec" variant of Ethernet cable, using special cable similar to RG-8/U coaxial cable. This is a stiff, diameter cable with an impedance of 50 ohms , a solid center conductor, a foam insulating filler, a shielding braid, and an outer jacket...
(thicknet) and
10BASE210BASE2 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
attenuationIn physics, attenuation is the gradual loss in intensity of any kind of flux through a medium. For instance, sunlight is attenuated by dark glasses, and X-rays are attenuated by lead....
,
characteristic impedanceThe characteristic impedance or surge impedance of a uniform transmission line, usually written , 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
jitterJitter is the time variation of a 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 periodic signals...
,
propagation delayPropagation delay is a technical term that can have a different meaning depending on the context. It can relate to networking, electronics or physics. In general it is the length of time taken for the quantity of interest to reach its destination.- Networking :...
, and several types of
noiseIn science, and especially in physics and telecommunication, noise is fluctuations in and the addition of external factors to the stream of target information being received at a detector. In communications, it may be deliberate as for instance jamming of a radio or TV signal, but in most cases it...
. 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-
gaugeAmerican wire gauge , also known as the Brown & Sharpe wire gauge, is a standardized wire gauge system used since 1857 predominantly in the United States for the diameters of round, solid, nonferrous, electrically conducting wire...
unshielded twisted-pair cable, and 100 meters is the stated maximum length for baseband signal runs. 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, though — as with all CSMA/CD network environments — the absolute limit on run length is determined by the size of the
collision domainA collision domain is a physical network segment where data packets can "collide" with one another for being sent on a shared medium, in particular in the Ethernet networking protocol. A network collision is a scenario wherein one particular device sends a packet on a network segment, forcing every...
and cable quality. In reality, what meets the standards may not work, and those that do not meet the standards might work.
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, though in practice category 5e or above is generally reccomended for 1000BASE-T. Furthermore while 10BASE-T is more tolerant of poor wiring such as
split pairA split pair is a wiring error where two connections that are supposed to be connected using the two wires of a twisted pair are instead connected using two wires from different pairs...
s, poor terminations and even use of short sections of flat cable, 100BASE-T is less tolerant, and 1000BASE-T is even less so. Since cable testing is often limited to checking if a connection works with Ethernet, running faster speeds over existing cable is often problematic. This problem is made worse by the fact that Ethernet's autonegotiation takes account only of the capabilities of the end equipment, not of the cable in between.
Autonegotiation and duplex mismatch
Many different modes of operations (10BASE-T half duplex, 10BASE-T full duplex, 100BASE-TX half duplex, ...) exist for Ethernet over
twisted 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.-...
, and most network adapters are capable of different modes of operations. In 1995, a standard was released to allow connected network adapters to negotiate the best possible shared mode of operation. The
autonegotiationAutonegotiation is an Ethernet procedure by which two connected devices choose common transmission parameters, such as speed and duplex mode. In this process, the connected devices first share their capabilities as for these parameters and then choose the fastest transmission mode they both...
standard contained a mechanism for detecting the speed but not the
duplexA duplex communication system is a system composed of two connected parties or devices that can communicate with one another in both directions...
setting of
EthernetEthernet is a family of frame-based computer networking technologies for local area networks . The name comes from the physical concept of the ether...
peers that did not use autonegotiation.
When two linked interfaces are set to different
duplexA duplex communication system is a system composed of two connected parties or devices that can communicate with one another in both directions...
modes, the effect of this
duplex mismatchIn 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.
The resulting
duplex mismatchIn 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...
results in a dramatically slow network, in which many
collisions, and especially
late collisionLate Collision is a type of collision found in the CSMA/CD protocol standard. If a collision error occurs after the first 512 bit times of data are transmitted by the transmitting station[IEEE , section 5.2.2.1.10], a late collision is said to have occurred...
s occur on the interface set to half-duplex, and
FCSA frame check sequence refers to the extra checksum characters added to a frame in a communication protocol for error detection and correction. Frames are used to send upper-layer data and ultimately the user application data from a source to a destination. The data package includes the message...
errors are seen on the full-duplex side.
Gigabit EthernetGigabit Ethernet is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second, as defined by the IEEE 802.3-2008 standard...
standards require autonegotiation to be on in order to operate.
See also
- 100BaseFX
- 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.-...
- IEEE 802.3
IEEE 802.3 is a collection of IEEE standards defining the Physical Layer and Data Link Layer's media access control sublayer of wired Ethernet. This is generally a LAN technology with some WAN applications...
- Ethernet physical layer
The Ethernet physical layer is the physical layer component of the Ethernet standard.The Ethernet physical layer evolved over a considerable time span and encompasses quite a few physical media interfaces and several magnitudes of speed...
- 25-pair color code
The 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...
- Computer network
A computer network is a group of interconnected computers. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of some types and categories and also presents the basic components of a network....
- Ethernet
Ethernet is a family of frame-based computer networking technologies for local area networks . The name comes from the physical concept of the ether...
- Fast Ethernet
In computer networking, Fast Ethernet is a collective term for a number of Ethernet standards that carry traffic at the nominal rate of 100 Mbit/s, against the original Ethernet speed of 10 Mbit/s. Of the 100 megabit Ethernet standards 100baseTX is by far the most common and is supported by the...
- Ethernet extender
An ethernet extender is any device used to extend an ethernet segment beyond its normal distance limitation which is approximately for most common forms of Ethernet...
- Network Isolators
- Power over Ethernet (PoE)
Power over Ethernet or PoE technology describes a system to safely transfer electrical power, along with data, to remote devices over standard category 5 cable in an Ethernet network...
- Wireless local loop
WLL redirects here. Not to be confused with Weight Load Limit, the maximum weight that a given apparatus can bearWireless local loop , is a term for the use of a wireless communications link as the "last mile / first mile" connection for delivering plain old telephone service and/or broadband...
(WLL)
External links