Material from PIE.Wiki. Ethernet standards and interfaces

Ethernet technology allows the use of various transmission media, for each of which there is a standard type name XBaseY, where X- transmission speed, Mbit / s (10, 100, 1000 ...); Base - keyword(denotes modulated transmission); Y- conventional designation of the transmission medium and communication range. All modern versions of Ethernet use twisted pair cable or fiber optic and star topology. The central arrangement of the star can be a repeater (aka a hub) or a switch. A point-to-point connection of two nodes is also possible. For older versions, the coaxial cable was characterized by a bus topology, the main disadvantage of which is the low reliability of the entire network. There is also an exotic version of the 10BaseFP passive optical bus. Sometimes networks use media converters(media converter) converting interface types. Converters of "twisted pair" to optics are most often used; converters of single-mode fiber to multimode are also used.

For Ethernet with a speed of 10 Mbps, the following standards exist.

? 10Base5- network on a thick coaxial cable RG-8 (50 Ohm) with bus topology, the maximum length of the cable segment is 500 m. network adapter must have an AUI interface connected by a cable release (4 shielded twisted pairs) to the transceiver installed on the cable. Currently, it is not used for new networks (expensive, cumbersome, ineffective and unpromising).

? 10Base2- network on a thin coaxial cable RG-58 (50 Ohm) with bus topology, the maximum length of the cable segment is 185 m. To connect, the network adapter must have a BNC interface connector (or AUI with a transceiver). This is the cheapest (in terms of equipment) network option; there are no prospects for development.

? 10BaseT- twisted pair network of category 3 and higher (2 pairs of wires), beam length - up to 100 m (on a cable of category 5, you can reach a distance of 200 m, but this is not recommended). To connect, the network adapter must have an RJ-45 interface connector (or AUI with a transceiver). it effective option the network entry level, allows you to expand the bandwidth by replacing repeater hubs with switches. With category 5 and higher cabling, it allows you to move at speeds of 100 and even 1000 Mbps (with the replacement of cards and hubs).

? 10BaseF and FOIRL- a network on a fiber optic cable (a pair of fibers). To connect, the adapter must have an AUI interface on which the optical transceiver is installed. Cheap multimode transceivers (wavelength - 850 nm) with a range of up to 1 km are used. For long distances (tens of kilometers on single-mode fiber), single-mode transceivers (1310 nm) are used, which can also work with multimode fiber (up to 2 km).

For networks Fast Ethernet with a speed of 100 Mbps, the following standards exist.

? 100BaseTX- twisted pair network of category 5 and higher (2 pairs of wires), beam length - up to 100 m. The network adapter is connected via an RJ-45 connector. This is a popular and optimal (price / performance) option for connecting nodes to the network. With high-quality cabling, it allows you to move to a speed of 1000 Mbit / s (with the replacement of cards and hubs).

? 100BaseT4- twisted pair network of category 3 and higher (4 pairs of wires), beam length - up to 100 m. RJ-45 connector, a rare option.

? 100BaseFX- a network on a fiber optic cable (a pair of fibers). Used single-mode transceivers (1310 nm), which can work with multi-mode fiber (up to 2 km). The range in full duplex mode is tens of kilometers.

? 100BaseSX- network on fiber optic cable with cheap multimode transceivers (850 nm), range - up to 300 m. Compatible with 10BaseF, auto-negotiation of mode and speed (10/100) is supported.

For networks Gigabit Ethernet with a speed of 1000 Mbps, the following standards exist.

? 1000BaseCX- connection of active equipment with a short (up to 25 m) STP cable or a two-axis cable.

? 1000BaseT- connection by twisted pair of category 5 and higher (4 pairs) at a distance of up to 100 m. RJ-45 connectors.

? 1000BaseSX- connection via a pair of multimode fibers, range - 200–500 m (depending on fiber parameters).

? 1000BaseLX- connection via a pair of single-mode fibers, range - up to 50 km (depending on the parameters of the transceivers).

Above were given the restrictions on the length of each physical connection in the network, however, for operability (reliable operation of the collision resolution protocol), additional conditions, described in detail in the literature, must also be met. The problem of reducing the diameter of the collision domain is solved by using switches, and overcoming collision restrictions on the length of each connection is ensured by switching to full-duplex communication mode (in which there are no collisions as such). For 10 Mbit networks Ethernet the following conditions must be met.

For coaxial - the rule "5-4-3": no more than 5 segments can connect no more than 4 repeaters, stations (adapters) can be connected in no more than 3 segments.

For twisted pair (and optics) - there can be no more than 4 repeaters (hubs) between any pair of nodes.

For any networks: the diameter of the collision domain - the largest distance (“electrical” cable length between a pair of nodes) - should not exceed 5 km.

The number of nodes in the collision domain is no more than 1024 (in reality, there should be no more than 30-50).

For networks Fast Ethernet the restrictions are tougher.

Collision domain diameter - no more than 205 m.

The number of repeaters in the collision domain is no more than two class II, no more than one class I.

V Gigabit Ethernet only switches are used, so only connection length restrictions apply.

For optical connections, the connectors used are various: ST, SC, MT-RJ and others. Coaxial connectors for "thick" and "thin" cables are different (series "N" and BNC respectively). Note that each coaxial segment must be terminated with 50 ohm terminators and grounded at one point. The “circuit ground” of the computer is not galvanically connected to the shield of the coaxial connector, so avoid accidentally touching the BNC connectors with metal parts that are connected to the computer chassis. Coaxial networks require proper grounding, violation of the rules is fraught with burnout of adapters.

For twisted pair, RJ-45 connectors are used (Fig. 10.1), the pin assignment of the network adapter connector (MDI port) is given in Table. 10.1. The ports on 10BaseT, 100BaseTX, and 100BaseT4 hubs are MDIX ports, with the TX and RX signals reversed. To connect end nodes to ports of active equipment (connection of MDI-MDIX ports, Fig.10.2, a) a "straight" cable is used (Fig. 10.3, a), for direct connection of adapters (MDI-MDI, Fig.10.2, b) or connecting two communication devices (MDIX-MDIX) use a "crossover" cable (Fig. 10.3, b). In communication devices, as a rule, one of the ports is equipped with an MDI-MDIX switch or an additional connector.

Rice. 10.1... RJ-45 connector: a- fork, b- socket

Table 10.1... RJ-45 connector for Ethernet adapter

Contact	10BaseT / 100BaseTX	100BaseT4	1000BaseTX
1	Tx +	Tx_D1 +	BI_D1 +
2	Tx-	Tx_D1-	BI_D1-
3	Rx +	Rx_D2 +	BI_D2 +
4	Not connected	BI_D3 +	BI_D3 +
5	Not connected	BI_D3-	BI_D3-
6	Rx-	Rx_D2-	BI_D2-
7	Not connected	BI_D4 +	BI_D4 +
8	Not connected	BI_D4-	BI_D4-

Rice. 10.2... 10BaseT / 100BaseTX network: a- star, b- point-to-point connection

Rice. 10.3... Ethernet interface cables: a- "straight", b- "cross"

V local area networks cable routing is usually used, consisting of fixed cables, terminated with plugs and patch cords. Fixed wiring is made so that it provides a "direct" connection of the pins of its interface connectors. Patch cords can be straight or crossover. Note that pin connections 4, 5, 7, and 8 are required only in 100BaseT4 and 1000BaseTX, but they do not interfere with 10BaseT and 100BaseTX, so the cabling is one.

Gigabit Ethernet 1000BaseTX uses straight-through cables only. The universal ports are Fast Ethernet compatible (auto-negotiate). If you connect two Gigabit Ethernet ports with a crossover cable, they will communicate in 100BaseTX mode.

For the above twisted-pair Ethernet implementations, mode negotiation protocol(autonegotiation), which is executed every time a connection is established after a physical connection and / or port initialization. The protocol is based on the exchange of service pulses (they are different from frames transmitted information). This protocol allows the connected ports to select the most efficient mode available to both ports. Mode priorities in descending order: 1000BaseT, 100BaseTX full duplex, 100BaseT4, 100BaseTX half duplex, 10BaseT full duplex, 10BaseT half duplex. The autonegotiation protocol can be disabled (or not implemented), in which case the mode of operation is forced when configuring the port. The ability to switch modes is reflected in the names of the ports (for example, Fast Ethernet 10/100); support for 100BaseT4 mode is not common.

For optical options, a matching protocol has also appeared, but its capabilities are limited due to the likely mismatch of wavelengths used in different options. True, autonegotiation is not so necessary here, since there are much fewer optical connections, they are carefully planned and not often reconfigured.

The Ethernet standard (10 Mbit / s) defines the AUI (Attachment Unit Interface) interface, with which a transceiver (transceiver) can be connected to the adapter for any transmission medium. The transceiver contains the terminal circuits of the transmitter, receiver and collision detector. The pin assignment of the AUI interface is shown in table. 10.2, a DB-15 connector is used here (female on adapter, male on transceiver).

Table 10.2... Ethernet AUI connector

Contact	Signal
1	Collision
2	Collision +
3	Transmit +
4	Receive (screen)
5	Receive +
6	DC Power GND
7	Not connected
8	Not connected
9	Collision -
10	Transmit -
11	Transmit (screen)
12	Receive -
13	DC Power (+ 12B)
14	DC Power (screen)
15	Not connected

The Fast Ethernet standard includes an MII (Media Independent Interface) interface. In MII, data for the receiver and transmitter are transmitted in uncoded form over 4-bit parallel buses (with a clock frequency of 2.5 and 25 MHz for speeds of 10 and 100 Mbps, respectively) or in serial code (for 10 Mbps). The interface contains signals of synchronization and control of the receiver and transmitter, line status (carrier presence, collision), as well as a serial control interface SMI (see section 11.2), through which you can communicate with the control registers of the transceiver. A physical connector for plugging in removable modules (40-pin, two-row) has also been identified, but it practically does not occur in a PC.

Tutorial

What is a collision domain?
How many pairs are used for Ethernet and why?
For which pairs is the reception, and for which transmission?
What limits the length of a network segment?
Why can't the frame be less than a certain size?

If you do not know the answers to these questions, but you are too lazy to read standards and serious literature on the topic, please, under cat.

Someone thinks that these are obvious things, others will say that a boring and unnecessary theory. Nevertheless, in interviews, you can periodically hear similar questions. My opinion: everyone who has to pick up the 8P8C crimp should be aware of what will be discussed below (this connector is usually mistakenly called RJ-45). I don’t pretend to be of academic depth, I will refrain from formulas and tables, and we will also leave linear coding overboard. It will be mainly about copper wires, not about optics, tk. they are more widespread in everyday life.

Ethernet technology describes the two lower layers of the OSI model at once. Physical and channel. In what follows, we will only talk about the physical, i.e. how bits are transferred between two neighboring devices.

Ethernet technology is part of the rich heritage of the Xerox PARC Research Center. Early versions of Ethernet used coaxial cable as the transmission medium, but over time it was completely replaced by fiber and twisted pair. However, it is important to understand that the use of coaxial cable largely determined how Ethernet works. The point is that coaxial cable is a shared transmission medium. An important feature of a shared environment: it can be used simultaneously by several interfaces, but only one should transmit at a time. Using a coaxial cable, you can connect not only 2 computers to each other, but also more than two, without the use of active equipment. This topology is called tire... However, if at least two nodes on the same bus start simultaneously transmitting information, then their signals will overlap and the receivers of other nodes will not understand anything. This situation is called collision, and the part of the network where the nodes compete for a common transmission medium is collision domain... In order to recognize a collision, the transmitting node constantly monitors the signals in the environment, and if its own transmitted signal differs from the observed one, a collision is recorded. In this case, all nodes stop transmitting and resume transmission through random time interval.

Collision domain diameter and minimum frame size

Now let's imagine what would happen if in the network shown in the figure, nodes A and C simultaneously start transmitting, but have time to finish it before they receive each other's signal. This is possible with a sufficiently short transmitted message and a sufficiently long cable, because as we know from the school curriculum, the propagation speed of any signals at best is C = 3 * 10 8 m / s. Because each of the transmitting nodes will receive the opposite signal only after it has finished transmitting its message - the fact that a collision has occurred will not be established by any of them, which means that there will be no retransmission of frames. But node B at the input will receive the sum of signals and will not be able to correctly receive any of them. In order to prevent such a situation from happening, it is necessary to limit the size of the collision domain and minimum frame size. It is not difficult to guess that these values are directly proportional to each other. If the amount of transmitted information does not reach the minimum frame, then it is increased due to the special pad field, the name of which can be translated as a placeholder.

Thus, the larger the potential size of the network segment, the more overhead is spent on transferring small data chunks. For developers Ethernet technologies I had to look for a middle ground between these two parameters, and the minimum frame size was set to 64 bytes.

Twisted pair and full duplex operation

Twisted pair as a transmission medium differs from coaxial cable in that it can connect only two nodes and uses separate media to transmit information in different directions. One pair is used for transmission (1,2 pins, usually orange and white-orange wires) and one pair for reception (3,6 pins, usually green and white-green wires). On active network equipment, vice versa. It is not difficult to notice that the central pair of contacts is missing: 4, 5. This pair was specially left free, if you insert RJ11 into the same socket, it will take just free contacts. Thus, you can use one cable and one socket, for LAN and, for example, a telephone. The pairs in the cable are chosen in such a way as to minimize the mutual influence of signals on each other and improve the quality of communication. The wires of one pair are twisted together so that the effect of external interference on both wires in a pair is approximately the same.
To connect two devices of the same type, for example, two computers, a so-called crossover cable is used, in which one pair connects contacts 1.2 of one side and 3.6 of the other, and the other, vice versa: 3.6 contacts of one side and 1 , 2 other. This is necessary in order to connect the receiver to the transmitter, if you use a straight cable, you get a receiver-receiver, transmitter-transmitter. Although now it only matters if you work with some archaic equipment, because almost all modern equipment supports Auto-MDIX - a technology that allows the interface to automatically determine which pair is receiving and which transmission.

The question arises: where does the restriction on the segment length of Ethernet over twisted pair come from if there is no shared medium? This is because the first twisted pair networks used hubs. A hub (in other words, a multi-input repeater) is a device that has several Ethernet ports and broadcasts the received packet to all ports except for the one from which the packet came. Thus, if the concentrator began to receive signals from two ports at once, then it did not know what to broadcast to the other ports, it was a collision. The same was true of the first Ethernet networks using optics (10Base-FL).

Why then use a 4-pair cable if only two of the 4 pairs are used? A reasonable question, and here are some reasons for doing this:

A 4-pair cable is mechanically more reliable than a 2-pair cable.
4-pair cable does not need to be changed when switching to Gigabit Ethernet or 100BaseT4, which already use all 4 pairs
If one pair is interrupted, you can use a free one instead of it and do not rearrange the cable.
Ability to use Power over ethernet technology

Despite this, in practice, they often use a 2-pair cable, connect 2 computers at once, one 4-pair cable, or use free pairs to connect a phone.

Gigabit Ethernet

Unlike its predecessors, Gigabit Ethernet always uses all 4 pairs for transmission simultaneously. Moreover, in two directions at once. In addition, the information is encoded not by two levels as usual (0 and 1), but by four (00,01,10,11). Those. the voltage level at any given moment encodes not one, but two bits at once. This is done in order to reduce the modulation frequency from 250 MHz to 125 MHz. In addition, a fifth level has been added to create code redundancy. It makes it possible to correct receiving errors. This type of coding is called five-level pulse amplitude coding (PAM-5). In addition, in order to use all pairs simultaneously To receive and transmit, the network adapter subtracts its own transmitted signal from the total signal to receive the signal transmitted by the other side. Thus, full duplex mode is realized over one channel.

Further more

10 Gigabit Ethernet it is already used by providers in its entirety, but it is not used in the SOHO segment, since apparently there is enough Gigabit Ethernet. 10GBE uses single and multimode fiber, with or without wavelength compression, copper cables with an InfiniBand connector and twisted pair in the 10GBASE-T or IEEE 802.3an-2006 standard.

40 Gigabit Ethernet (or 40GbE) and 100 Gigabit Ethernet (or 100GbE). The development of these standards was completed in July 2010. Currently, leading manufacturers of network equipment such as Cisco, Juniper Networks and Huawei are already engaged in the development and release of the first routers supporting these technologies. Add tags

Ethernet standards define wired connections and electrical signals at the physical layer, the format
frames and media access control protocols - at the link layer of the OSI model. Ethernet is mainly
described by the IEEE 802.3 standards. Ethernet has become the most widespread LAN technology in the middle
90s of the last century, replacing outdated technologies such as Arcnet, FDDI and Token ring.

History of creation

Ethernet technology was developed in conjunction with many of Xerox PARC's early projects.
It is generally accepted that Ethernet was invented on May 22, 1973, when Robert Metcalfe
wrote a memo for the head of PARC on the potential of Ethernet technology. But the legal right to
Metcalfe received the technology a few years later. In 1976 he and his assistant David Boggs
published a brochure titled Ethernet: Distributed Packet-Switching For Local Computer Networks.

Metcalfe left Xerox in 1979 and founded 3Com to promote computers and local
computer networks (LAN). He managed to convince DEC, Intel and Xerox to work together and develop
Ethernet standard (DIX). This standard was first published on September 30, 1980. He started
rivalry with two major patented technologies: token ring and ARCNET - which were soon
buried under the rolling waves of Ethernet products. In the process of struggle, 3Com became the main company
in this industry.

Technology

The standard of the first versions (Ethernet v1.0 and Ethernet v2.0) specifies that as the transmission medium
coaxial cable is used, later it became possible to use twisted pair and optical
cable.

The reasons for the transition were:

the ability to work in duplex mode;
low cost of "twisted pair" cable;
higher reliability of networks in the event of a cable fault;
high noise immunity when using a differential signal;
Possibility of power supply by cable to low-power nodes, for example, IP-phones (Power over Ethernet, POE standard);
lack of galvanic connection (current flow) between network nodes. When using a coaxial cable in Russian conditions, where, as a rule, there is no grounding of computers, the use of a coaxial cable was often accompanied by a breakdown of network cards, and sometimes even a complete "burnout" of the system unit.

The reason for the transition to optical cable was the need to increase the segment length without repeaters.

Access Control Method (For Network On) - Carrier Sense Multiple Access and
collision detection (CSMA / CD, Carrier Sense Multiple Access with Collision Detection), baud rate
data 10 Mbit / s, packet size from 72 to 1526 bytes, data encoding methods are described. Working hours
half-duplex, that is, a node cannot simultaneously transmit and receive information. Number of nodes in
one shared network segment is limited to a limit of 1024 workstations (specifications
the physical layer can set more stringent restrictions, for example, to the thin coaxial segment
no more than 30 workstations can be connected, and no more than 100 can be connected to the thick coaxial segment). but
a network built on one shared segment becomes ineffective long before reaching
limit value of the number of nodes, mainly due to half-duplex operation.

In 1995, the IEEE 802.3u Fast Ethernet standard was adopted at a speed of 100 Mbit / s and it became possible
full duplex operation. In 1997, the IEEE 802.3z Gigabit Ethernet standard was adopted with the speed
1000 Mbps for transmission over optical fiber and two years later for transmission over twisted pair.

Ethernet varieties

There are several technology options depending on the data transfer rate and the transmission medium.
Regardless of the method of transferring the stack network protocol and the programs work the same in almost
all of the options listed below.

Most Ethernet cards and other devices have support for multiple baud rates,
using autonegotiation of speed and duplex to achieve the best
connections between two devices. If autodetection fails, the speed adjusts to
partner, and half-duplex transmission is enabled. For example, the presence of an Ethernet port in the device
10/100 means that through it you can work using 10BASE-T and 100BASE-TX technologies, and the port
Ethernet 10/100/1000 - Supports 10BASE-T, 100BASE-TX, and 1000BASE-T standards.
Early Ethernet modifications

Xerox Ethernet - original technology, 3Mbps speed, existed in two versions Version 1 and Version 2, frame format latest version is still widely used.
10BROAD36 - not widespread. One of the first standards to allow long distance work. Used a wideband modulation technology similar to that used
in cable modems. A coaxial cable was used as a data transmission medium.
1BASE5 - also known as StarLAN, was the first modification of Ethernet technology to use twisted pair cables. It worked at a speed of 1 Mbit / s, but did not find commercial use.

10 Mbps Ethernet

10BASE5, IEEE 802.3 (also called "Thick Ethernet") was the original development of a technology with a data transfer rate of 10 Mbps. Following an early IEEE standard, it uses a 50 ohm coaxial cable (RG-8), with a maximum segment length of 500 meters.
10BASE2, IEEE 802.3a (called "Thin Ethernet") - RG-58 cable is used, with a maximum segment length of 185 meters, computers were connected to one another to connect the cable to the network
the card needs a T-connector and the cable needs a BNC connector. Terminators are required on each
end. For many years this standard has been the main standard for Ethernet technology.
StarLAN 10 - The first design to use twisted pair cable for data transmission at 10 Mbps.

Later it evolved into the 10BASE-T standard.

Despite the fact that it is theoretically possible to connect more than
two devices operating in simplex mode, such a scheme is never used for Ethernet, in
the difference from working with. Therefore, all twisted pair networks use a star topology,
while, coaxial cable networks are based on a bus topology. Terminators for work on
twisted pair cables are built into each device, and there is no need to use additional external terminators in the line.

10BASE-T, IEEE 802.3i - 4 twisted pair cables (twisted pair) of Category-3 or Category-5 are used for data transmission. The maximum segment length is 100 meters.
FOIRL - (acronym for Fiber-optic inter-repeater link). Basic standard for Ethernet technology using optical cable for data transmission. The maximum data transmission distance without repeater is 1 km.
10BASE-F, IEEE 802.3j - The main term for a family of 10 Mbps ethernet standards using optical cable up to 2 kilometers away: 10BASE-FL, 10BASE-FB, and 10BASE-FP. Of the above, only 10BASE-FL is widely used.
10BASE-FL (Fiber Link) - An improved version of the FOIRL standard. The improvement concerned an increase in the segment length up to 2 km.
10BASE-FB (Fiber Backbone) - Now an unused standard, it was intended for combining repeaters into a backbone.
10BASE-FP (Fiber Passive) - Passive star topology that does not require repeaters - has never been used.

Fast Ethernet (Fast Ethernet, 100 Mbps)

100BASE-T is a general term for standards used as a data transmission medium. Segment length up to 100 meters. Includes 100BASE-TX, 100BASE-T4 and 100BASE-T2 standards.
100BASE-TX, IEEE 802.3u is an evolution of the 10BASE-T standard for use in star networks. A twisted pair of category 5 is used, in fact, only two unshielded pairs of conductors are used, full-duplex data transmission is supported, a distance of up to 100 m.
100BASE-T4 is a standard using a twisted pair of category 3. All four pairs of conductors are involved, data transmission is in half duplex. Practically not used.
100BASE-T2 is a Category 3 twisted pair standard. Only two pairs of conductors are used. Full duplex is supported, where signals propagate in opposite directions on each pair. The transmission rate in one direction is 50 Mbps. Practically not used.
100BASE-SX is a standard using multimode fiber. The maximum segment length is 400 meters in half duplex (for guaranteed collision detection) or 2 kilometers in full duplex.
100BASE-FX is a standard using single mode fiber. The maximum length is limited only
the amount of attenuation in the optical cable and the power of the transmitters, according to different materials from 2x to 10
kilometers
100BASE-FX WDM is a standard using single mode fiber. The maximum length is limited only
the amount of attenuation in the fiber-optic cable and the power of the transmitters. There are two interfaces
types, differ in the transmitter wavelength and are marked with either numbers (wavelength) or one Latin
the letter A (1310) or B (1550). Only paired interfaces can work in pairs: on one side the transmitter
at 1310 nm, and on the other - at 1550 nm.

Gigabit Ethernet (Gigabit Ethernet, 1 Gbps)

1000BASE-T, IEEE 802.3ab is a Category 5e twisted pair cable standard. 4 pairs are involved in data transfer. The data transfer rate is 250 Mbps over one pair. The coding method is PAM5, the fundamental frequency is 62.5 MHz. Distance up to 100 meters
1000BASE-TX was created by the Telecommunications Industry Association.
Industry Association, TIA) and published in March 2001 as "Physical Layer Specification
duplex Ethernet 1000 Mbps (1000BASE-TX) symmetric Cat 6 cabling
(ANSI / TIA / EIA-854-2001) "(eng." A Full Duplex Ethernet Specification for 1000 Mbis / s (1000BASE-TX)
Operating Over Category 6 Balanced Twisted-Pair Cabling (ANSI / TIA / EIA-854-2001) "). Standard, uses
separate reception and transmission (one pair in each direction), which greatly simplifies the design
transceiver devices. Another significant difference between 1000BASE-TX is the lack of a circuit
digital compensation of pickup and return noise, resulting in complexity, power consumption
and the price of processors becomes lower than that of 1000BASE-T processors. But, as a consequence, for
stable operation of this technology requires a cable system High Quality so 1000BASE-TX
can only use Category 6 cable. Based of this standard almost never been created
products, although 1000BASE-TX uses a simpler protocol than the 1000BASE-T standard and therefore can
use simpler electronics.
1000BASE-X is a generic term for standards with pluggable GBIC or SFP transceivers.
1000BASE-SX, IEEE 802.3z is a standard using multimode fiber. Distance of passage
signal without repeater up to 550 meters.
1000BASE-LX, IEEE 802.3z is a standard using single-mode fiber. Distance of passage
signal without repeater up to 5 kilometers.
used.
1000BASE-CX - standard for short distances (up to 25 meters) using twinaxial cable
with a characteristic impedance of 75 Ohm (each of the two waveguides). Replaced by 1000BASE-T standard and no longer
used.
1000BASE-LH (Long Haul) is a standard using single mode fiber. Distance of passage
signal without repeater up to 100 kilometers.

10 Gigabit Ethernet

The new 10 Gigabit Ethernet standard includes seven physical media standards for LAN, MAN and
WAN. It is currently covered by the IEEE 802.3ae amendment and should be included in the next revision.
IEEE 802.3 standard.

10GBASE-CX4 - 10 Gigabit Ethernet technology for short distances (up to 15 meters) using CX4 copper cable and InfiniBand connectors.
10GBASE-SR - 10 Gigabit Ethernet technology for short distances (up to 26 or 82 meters, in
depending on cable type), multimode fiber is used. It also supports distances up to 300
meters using new multimode fiber (2000 MHz / km).
10GBASE-LX4 - Uses wavelength division multiplexing to support distances from 240 to 300 meters over multimode fiber. Also supports distances up to 10 kilometers when using single-mode
fibers.
10GBASE-LR and 10GBASE-ER - these standards support distances up to 10 and 40 kilometers
respectively.
10GBASE-SW, 10GBASE-LW, and 10GBASE-EW - These standards use a physical interface that is compatible
by speed and data format with OC-192 / STM-64 SONET / SDH interface. They are similar to the 10GBASE-SR standards,
10GBASE-LR and 10GBASE-ER respectively, since they use the same cable types and transmission distances.
10GBASE-T, IEEE 802.3an-2006 - adopted in June 2006 after 4 years of development. Uses
shielded twisted pair. Distances - up to 100 meters.

History

Ethernet technology was developed in conjunction with many of Xerox PARC's early projects. It is generally accepted that Ethernet was invented on May 22, 1973, when Robert Metcalfe ( Robert metcalfe) wrote a memo for the head of PARC on the potential of Ethernet technology. But Metcalfe acquired the legal right to the technology a few years later. In 1976, he and his assistant David Boggs published a brochure entitled "Ethernet: Distributed Packet-Switching For Local Computer Networks." R. M. Metcalfe and D. R. Boggs... Ethernet: Distributed Packet Switching for Local Computer Networks. // ACM Communications, 19 (5): 395-404, July 1976.

Metcalfe left Xerox in 1979 and founded 3Com to promote computers and local area networks (LANs). He managed to convince DEC, Intel and Xerox to work together and develop the Ethernet standard (DIX). This standard was first published on September 30, 1980. It began a rivalry with two major patented technologies, Token Ring and Arcnet, which were soon buried under the rolling waves of Ethernet products. In the process, 3Com became the main company in the industry.

Technology

The standard of the first versions (Ethernet v1.0 and Ethernet v2.0) specifies that a coaxial cable is used as a transmission medium, later it became possible to use twisted pair and optical cable.

Popular types of Ethernet are designated as 10Base2, 100BaseTX, etc. Here, the first element denotes the transmission speed, Mbps. Second element:

Base - direct (unmodulated) transmission,
Broad - Uses broadband cable with frequency division multiplexing.

Third element: rounded cable length in hundreds of meters (10Base2 - 185 m, 10Base5 - 500 m) or transmission medium (T, TX, T2, T4 - twisted pairs, FX, FL, FB, SX and LX - optical fiber, CX - twinaxial cable for Gigabit Ethernet).

The reasons for the switch to twisted pair were:

the ability to work in duplex mode;
low cost of "twisted pair" cable;
higher reliability of networks in the event of a cable fault;
high noise immunity when using a differential signal;
Possibility of power supply by cable to low-power nodes, for example, IP-phones (Power over Ethernet, POE standard);
lack of galvanic connection (current flow) between network nodes. When using a coaxial cable in Russian conditions, where, as a rule, there is no grounding of computers, the use of a coaxial cable was often accompanied by a breakdown of network cards, and sometimes even a complete "burnout" of the system unit.

The reason for the transition to optical cable was the need to increase the segment length without repeaters.

Access control method (for network on coaxial cable) - multiple access with carrier sense and collision detection (CSMA / CD, Carrier Sense Multiple Access with Collision Detection), data rate 10 Mbit / s, packet size from 72 to 1526 bytes, described data encoding methods. The operating mode is half-duplex, that is, the node cannot simultaneously transmit and receive information. The number of nodes in one shared network segment is limited by the limit value of 1024 workstations (physical layer specifications can set more stringent restrictions, for example, no more than 30 workstations can be connected to a thin coaxial segment, and no more than 100 to a thick coaxial segment). However, a network built on a single shared segment becomes ineffective long before the limit on the number of nodes is reached, mainly due to half-duplex operation.

Most Ethernet cards and other devices support multiple baud rates using autonegotiation of speed and duplex to achieve the best possible connection between the two devices. If auto-sensing does not work, the speed adjusts to the partner, and half-duplex transmission is turned on. For example, the presence of an Ethernet 10/100 port in the device means that it can operate using 10BASE-T and 100BASE-TX technologies, and the Ethernet 10/100/1000 port supports 10BASE-T, 100BASE-TX and 1000BASE- T.

Early Ethernet modifications

Xerox Ethernet- the original technology, 3Mbit / s, existed in two versions, Version 1 and Version 2, the frame format of the latest version is still widely used.
10BROAD36- did not receive wide distribution. One of the first standards to allow long distance work. Used broadband modulation technology similar to that used in cable modems. A coaxial cable was used as a data transmission medium.
1BASE5- also known as StarLAN, was the first modification of Ethernet technology to use a twisted pair cable. It worked at a speed of 1 Mbit / s, but did not find commercial use.

10 Mbps Ethernet

10BASE5, IEEE 802.3 (also called "Thick Ethernet") was the original development of a technology with a data transfer rate of 10 Mbps. Following an early IEEE standard, it uses a 50 ohm coaxial cable (RG-8), with a maximum segment length of 500 meters.
10BASE2, IEEE 802.3a (called "Thin Ethernet") - RG-58 cable is used, with a maximum segment length of 200 meters, computers were connected to one another, to connect the cable to network card you need a T-connector and the cable must have a BNC connector. Terminators are required at each end. For many years this standard has been the main standard for Ethernet technology.
StarLAN 10- The first development using twisted pair cable for data transmission at a speed of 10 Mbit / s. Later it evolved into the 10BASE-T standard.

Although it is theoretically possible to connect more than two devices operating in simplex mode to one twisted pair cable (segment), such a scheme is never used for Ethernet, in contrast to working with coaxial cable. Therefore, all twisted pair networks use a star topology, while coax networks use a bus topology. Twisted-pair terminators are built into each device, and there is no need to use additional external terminators on the line.

10BASE-T, IEEE 802.3i - for data transmission, 4 wires of a twisted pair cable (two twisted pairs) of category-3 or category-5 are used. The maximum segment length is 100 meters.
FOIRL- (acronym for Fiber-optic inter-repeater link). Basic standard for Ethernet technology using optical cable for data transmission. The maximum data transmission distance without repeater is 1 km.
10BASE-F, IEEE 802.3j - The main term for a family of 10 Mbps ethernet standards using fiber optic cables up to 2 kilometers away: 10BASE-FL, 10BASE-FB, and 10BASE-FP. Of the above, only 10BASE-FL is widely used.
10BASE-FL(Fiber Link) - Improved version of the FOIRL standard. The improvement concerned an increase in the segment length up to 2 km.
10BASE-FB(Fiber Backbone) - Now an unused standard, it was intended for combining repeaters into a backbone.
10BASE-FP(Fiber Passive) - Passive star topology that does not require repeaters - never used.

Fast Ethernet (Fast Ethernet, 100 Mbps)

100BASE-T is a general term for standards using twisted pair as a data transmission medium. Segment length up to 100 meters. Includes 100BASE-TX, 100BASE-T4 and 100BASE-T2 standards.
100BASE-TX, IEEE 802.3u is an evolution of the 10BASE-T standard for use in star networks. A twisted pair of category 5 is used, in fact, only two unshielded pairs of conductors are used, full-duplex data transmission is supported, a distance of up to 100 m.
100BASE-T4- a standard using a twisted pair of category 3. All four pairs of conductors are involved, data transmission is in half duplex. Practically not used.
100BASE-T2- a standard using a twisted pair of category 3. Only two pairs of conductors are involved. Full duplex is supported, where signals propagate in opposite directions on each pair. The transmission rate in one direction is 50 Mbps. Practically not used.
100BASE-SX is a standard using multimode fiber. The maximum segment length is 400 meters in half duplex (for guaranteed collision detection) or 2 kilometers in full duplex.
100BASE-FX is a standard using single-mode fiber. The maximum length is limited only by the attenuation in the fiber optic cable and the power of the transmitters.
100BASE-FX WDM is a standard using single-mode fiber. The maximum length is limited only by the attenuation in the fiber optic cable and the power of the transmitters. Interfaces are of two types, differ in the transmitter wavelength and are marked with either numbers (wavelength) or one Latin letter A (1310) or B (1550). Only paired interfaces can work in pairs: on the one hand, the transmitter is at 1310 nm, and on the other, at 1550 nm.

Fast Ethernet

Fast Ethernet (IEEE802.3u, 100BASE-X) is a set of standards for data transmission in computer networks, at speeds up to 100 Mbit / s, as opposed to conventional Ethernet (10 Mbit / s).

Gigabit Ethernet (Gigabit Ethernet, 1 Gbps)

1000BASE-T IEEE 802.3ab is a standard using Category 5e twisted pair cable. All 4 pairs are involved in data transfer. The data rate is 250 Mbps over one pair. The coding method is PAM5, the fundamental frequency is 62.5 MHz.
1000BASE-TX was created by the Telecommunications Industry Association (eng. Telecommunications Industry Association, TIA) and published in March 2001 as the Physical Layer Specification for Duplex Ethernet 1000 Mbps (1000BASE-TX) Category 6 Symmetric Cabling Systems (ANSI / TIA / EIA-854-2001). "A Full Duplex Ethernet Specification for 1000 Mbis / s (1000BASE-TX) Operating Over Category 6 Balanced Twisted-Pair Cabling (ANSI / TIA / EIA-854-2001)"). The standard uses separate transmission and reception (1 pair for transmission, 1 pair for reception, data is transmitted at a speed of 500 Mbit / s for each pair), which greatly simplifies the design of transceiver devices. But, as a consequence, for stable operation with this technology, a high quality cable system is required, so 1000BASE-TX can only use Category 6 cable. Another significant difference of 1000BASE-TX is the absence of a digital compensation circuit for pickups and return noise, as a result of which the complexity, power consumption level and the price of processors becomes lower than that of 1000BASE-T processors. There are practically no products based on this standard, although 1000BASE-TX uses a simpler protocol than the 1000BASE-T standard, and therefore can use simpler electronics.
1000BASE-X is a general term for standards with pluggable GBIC or SFP transceivers.
1000BASE-SX, IEEE 802.3z is a standard using multimode fiber. Signal transmission range without repeater is up to 550 meters.
1000BASE-LX IEEE 802.3z is a standard using single-mode fiber. Signal transmission range without repeater is up to 80 kilometers.
1000BASE-CX- the standard for short distances (up to 25 meters) using a twinax cable with a characteristic impedance of 150 ohms. Replaced by 1000BASE-T standard and is not used now.
1000BASE-LH(Long Haul) is a standard using single-mode fiber. Signal transmission range without repeater is up to 100 kilometers.

10 Gigabit Ethernet

The new 10 Gigabit Ethernet standard includes seven physical media standards for LAN, MAN and WAN. It is currently covered by the IEEE 802.3ae amendment and should be included in the next revision of the IEEE 802.3 standard.

10GBASE-CX4- 10 Gigabit Ethernet technology for short distances (up to 15 meters) using CX4 copper cable and InfiniBand connectors.
10GBASE-SR- 10 Gigabit Ethernet technology for short distances (up to 26 or 82 meters, depending on the type of cable), using multimode fiber. It also supports distances up to 300 meters using new multimode fiber (2000 MHz / km).
10GBASE-LX4- Uses wavelength division multiplexing to support distances from 240 to 300 meters over multimode fiber. Also supports distances up to 10 kilometers when using single-mode fiber.
10GBASE-LR and 10GBASE-ER- these standards support distances of up to 10 and 40 kilometers, respectively.
10GBASE-SW, 10GBASE-LW and 10GBASE-EW- These standards use a physical interface that is speed and data format compatible with the OC-192 / STM-64 SONET / SDH interface. They are similar to the 10GBASE-SR, 10GBASE-LR and 10GBASE-ER standards respectively, as they use the same cable types and transmission distances.
10GBASE-T, IEEE 802.3an-2006 - adopted in June 2006 after 4 years of development. Uses shielded twisted pair cable. Distances - up to 100 meters.

The 10 Gigabit Ethernet standard is still too young, so it will take time to understand which of the above standards for transmission media will actually be in demand on the market. 10 Gigabits / second is not the limit yet. Development of 1000 G Ethernet and higher is already underway.