Ethernet physical layer

The Ethernet physical layer is the physical layer functionality of the Ethernet family of computer network standards. The physical layer defines the electrical or optical properties of the physical connection between a device and the network or between network devices. It is complemented by the MAC layer and the logical link layer.

Ethernet physical layer
A standard 8P8C (often called RJ45) connector used most commonly on category 5 cable, one of the types of cabling used in Ethernet networks
Standard IEEE 802.3 (1983 onwards)
Physical media Coaxial cable, twisted pair, optical fiber
Network topology Point-to-point, star, bus
Major variants 10BASE5, 10BASE2, 10BASE-T, 100BASE-TX, 1000BASE-T, 10GBASE-T
Maximum distance 100 m (328 ft) over twisted pair, up to 100 km over optical fiber
Mode of operation differential (balanced), optical, single-ended
Maximum bit rate 1 Mbit/s to 400 Gbit/s
Voltage levels ± 2.5 V (over twisted pair)
Common connector types 8P8C, LC, SC, ST

The Ethernet physical layer has evolved over its existence starting in 1980 and encompasses multiple physical media interfaces and several orders of magnitude of speed from 1 Mbit/s to 400 Gbit/s. The physical medium ranges from bulky coaxial cable to twisted pair and optical fiber with a standardized reach of up to 40 km. In general, network protocol stack software will work similarly on all physical layers.

Many Ethernet adapters and switch ports support multiple speeds by using autonegotiation to set the speed and duplex for the best values supported by both connected devices. If autonegotiation fails, some multiple-speed devices sense the speed used by their partner,[1] but this may result in a duplex mismatch. With rare exceptions, a 100BASE-TX port (10/100) also supports 10BASE-T while a 1000BASE-T port (10/100/1000) also supports 10BASE-T and 100BASE-TX. Most 10GBASE-T ports also support 1000BASE-T,[2] some even 100BASE-TX or 10BASE-T. While autonegotiation can practically be relied on for Ethernet over twisted pair, few optical-fiber ports support multiple speeds. In any case, even multi-rate fiber interfaces only support a single wavelength (e.g. 850 nm for 1000BASE-SX or 10GBASE-SR).

10 Gigabit Ethernet was already used in both enterprise and carrier networks by 2007, with 40 Gbit/s[3][4] and 100 Gigabit Ethernet[5] ratified.[6] In 2017, the fastest additions to the Ethernet family were 200 and 400 Gbit/s.[7]

Naming conventions

Generally, layers are named by their specifications:[8]

  • 10, 100, 1000, 10G, ... – the nominal, usable speed at the top of the physical layer (no suffix = megabit/s, G = gigabit/s), excluding line codes but including other physical layer overhead (preamble, SFD, IPG); some WAN PHYs (W) run at slightly reduced bitrates for compatibility reasons; encoded PHY sublayers usually run at higher bitrates
  • BASE, BROAD, PASS – indicates baseband, broadband, or passband signaling respectively
  • -T, -S, -L, -E, -Z, -C, -K, -H ... – medium (PMD): T = twisted pair, S = 850 nm short wavelength (multi-mode fiber), L = 1300 nm long wavelength (mostly single-mode fiber), E or Z = 1500 nm extra long wavelength (single-mode), B = bidirectional fiber (mostly single-mode) using WDM, P = passive optical (PON), C = copper/twinax, K = backplane, 2 or 5 or 36 = coax with 185/500/3600 m reach (obsolete), F = fiber, various wavelengths, H = plastic optical fiber
  • X, R – PCS encoding method (varying with the generation): X for 8b/10b block encoding (4B5B for Fast Ethernet), R for large block encoding (64b/66b)
  • 1, 2, 4, 10 – for LAN PHYs indicates number of lanes used per link; for WAN PHYs indicates reach in kilometers

For 10 Mbit/s, no encoding is indicated as all variants use Manchester code. Most twisted pair layers use unique encoding, so most often just -T is used.

The reach, especially for optical connections, is defined as the maximum achievable link length that is guaranteed to work when all channel parameters are met (modal bandwidth, attenuation, insertion losses etc). With better channel parameters, often a longer, stable link length can be achieved. Vice versa, a link with worse channel parameters can also work but only over a shorter distance. Reach and maximum distance have the same meaning.

Physical layers

The following sections provide a brief summary of official Ethernet media types. In addition to these official standards, many vendors have implemented proprietary media types for various reasons—often to support longer distances over fiber optic cabling.

Early implementations
See also: Classic Ethernet

Early Ethernet standards used Manchester coding so that the signal was self-clocking and not adversely affected by high-pass filters.

Name Standard (Clause) Common connectors Link reach Required cable Description
Coaxial cable
Xerox experimental Ethernet Proprietary Vampire tap 1 km 75 Ω coaxial The original 2.94 Mbit/s Ethernet implementation had eight-bit addresses and other differences in frame format.[9]
10BASE5 802.3-1983 (8) AUI, N, vampire tap 500 m RG-8X Original standard uses a single coaxial cable in which a connection is made by tapping into the single cable, drilling in to make contact with the core and the screen. Largely obsolete, though due to its widespread deployment in the early 1980s, some systems may still be in use.[10] Was known also as DIX Standard (pre 802.3) and later as Thick-Ethernet (in contrast to 10BASE2, thinnet). 10 Mbit/s over expensive RG-8X 50 Ω coaxial cabling, electrical bus topology with collision detection. Deprecated 2003.
10BASE2 802.3a-1985 (10) BNC, EAD/TAE-E 185 m RG-58 50 Ω coaxial cable connects machines together, each machine using a T-connector to connect to its NIC. Requires terminators at each end. For many years during the mid to late 1980, this was the dominant Ethernet standard. Also called Thin Ethernet, Thinnet or Cheapernet. 10 Mbit/s over RG-58 coaxial cabling, bus topology with collision detection. Deprecated 2011.
10BROAD36 802.3b-1985 (11) F 1800 m @VF0.87[11] 75 Ω coaxial An early standard supporting Ethernet over longer distances. It utilized broadband modulation techniques, similar to those employed in cable modem systems, and operated over coaxial cable. 10 Mbit/s, scrambled NRZ signaling modulated (PSK) over high frequency carrier, broad bandwidth coaxial cabling, bus topology with collision detection. Deprecated 2003.
Twisted-pair cable
1BASE5 802.3e-1987 (12) 8P8C (IEC 60603-7) 250 m voice-grade Also called StarLAN. Operated at 1 Mbit/s over twisted pair to an active hub, star topology. Although a commercial failure, 1BASE5 defined the architecture for all subsequent Ethernet evolution on twisted pair. Deprecated 2003.
StarLAN 10 Proprietary (1988) 8P8C 100 m voice-grade 10 Mbit/s over copper twisted pair cabling, star topology – evolved into 10BASE-T
LattisNet UTP Proprietary (1987) 8P8C 100 m voice-grade 10 Mbit/s over copper twisted pair cabling, star topology – evolved into 10BASE-T
10BASE-T 802.3i-1990 (14) 8P8C (IEC 60603-7) 100 m Cat-3 Runs over four wires (two twisted pairs). A repeater hub 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. Copper twisted pair cabling, star topology – direct evolution of 1BASE-5. As of 2018, still widely supported.
10BASE-Te 802.3az-2010 (14) 100 m Cat-5 Energy-efficient Ethernet variant of 10BASE-T using a reduced amplitude signal over Category 5 cable, completely interoperable with 10BASE-T nodes.
10BASE-T1 802.3cg-2019 (tba) 15/25/1000 m Ethernet over a single twisted pair for automotive and industrial applications, including PoDL
Fiber-optical cable
FOIRL 802.3d-1987 (9.9) ST 1000 m FDDI-style MMF Fiber-optic inter-repeater link; the original standard for Ethernet over fiber, superseded by 10BASE-FL
10BASE-F 802.3j-1993 (15) A generic term for the family of 10 Mbit/s Ethernet standards using fiber optic cable: 10BASE-FL, 10BASE-FB and 10BASE-FP. Of these only 10BASE-FL gained widespread use. 10 Mbit/s over fiber pair
10BASE-FL 802.3j-1993 (15&18) ST 2000 m FDDI-style MMF An updated version of the FOIRL standard for end nodes, 2 km reach over FDDI-style multi-mode fiber, 850 nm wavelength
10BASE-FB 802.3j-1993 (15&17) 2000 m Intended for backbones connecting a number of hubs or switches as a direct successor to FOIRL; deprecated 2011.[12]
10BASE‑FP 802.3j-1993 (15&16) 1000 m A passive star network that required no repeater, it was never implemented.[12] Deprecated 2003.

Fast Ethernet
Main article: Fast Ethernet

All Fast Ethernet variants use a star topology and generally use 4B5B line coding.

Name Standard (Clause) Common connectors Description
Twisted-pair cable
100BASE‑T802.3u-1995 (21)A term for any of the three standards for 100 Mbit/s Ethernet over twisted pair cable. Includes 100BASE-TX, 100BASE-T4 and 100BASE-T2. As of 2009, 100BASE-TX has totally dominated the market, and may be considered synonymous with 100BASE-T in informal usage.
100BASE-TX802.3u-1995 (24, 25)8P8C (FDDI TP-PMD standard, ANSI INCITS 263-1995)4B5B MLT-3 coded signaling, Category 5 cable using two twisted pairs. As of 2018, still very popular.
100BASE-T4802.3u-1995 (23)8P8C (IEC 60603-7)8B6T PAM-3 coded signaling, Category 3 cable (as used for 10BASE-T installations) using four twisted pairs. Limited to half-duplex. Deprecated 2003.
100BASE-T2802.3y-1998 (32)8P8C (IEC 60603-7)PAM-5 coded signaling, CAT3 copper cabling with two twisted pairs, star topology. Supports full-duplex. It is functionally equivalent to 100BASE-TX, but supports old telephone cable. However, special sophisticated digital signal processors are required to handle encoding schemes required, making this option fairly expensive at the time. It arrived well after 100BASE-TX was established in the market. 100BASE-T2 and 100BASE-T4 were not widely adopted but the some of the technology developed for them is used in 1000BASE-T.[12] Deprecated 2003.
100BASE-T1802.3bw-2015 (96)none specifiedUses PAM-3 modulation at 66.7 MBd over a single, bi-directional twisted pair of up to 15 m; three bits are encoded as two ternary symbols. It is intended for automotive applications.
100BaseVG802.12-19948P8CStandardized by a different IEEE 802 subgroup, 802.12, because it used a different, more centralized form of media access (demand priority). Proposed by Hewlett-Packard. Inherently half-duplex, it needed four pairs in a Cat-3 cable. Now obsolete, the standard has been withdrawn in 2001.
HDMI Ethernet ChannelHDMI 1.4 (2009)HDMIHEC uses a hybrid to mix and separate 100BASE-TX's transmit and receive signals through a single twisted pair.
Fiber-optical cable
100BASE‑FX802.3u-1995 (24, 26)ST, SC4B5B NRZI coded signaling, two strands of multi-mode optical fiber. Maximum length is 400 meters for half-duplex connections (to ensure collisions are detected) or 2 kilometers for full-duplex. The specifications are largely borrowed from FDDI.
100BASE‑SXTIA-785 (2000)ST, SC100 Mbit/s Ethernet over multi-mode fiber. Maximum length is 300 meters. 100BASE-SX used short wavelength (850 nm) optics that was sharable with 10BASE-FL, thus making an autonegotiation scheme possible with 10/100 fiber adapters.
100BASE‑BX10802.3ah-2004 (58, 66)ST, SC, LC100 Mbit/s Ethernet bidirectionally over a single strand of single-mode optical fiber. An optical multiplexer is used to split transmit and receive signals into different wavelengths allowing them to share the same fiber. Supports up to 10 km, full-duplex only.[13]
100BASE-LX10802.3ah-2004 (58)ST, SC, LC100 Mbit/s Ethernet up to 10 km over a pair of single-mode fibers, full-duplex only.[13]

1 Gbit/s
Main article: Gigabit Ethernet

All Gigabit Ethernet variants use a star topology. 1000BASE-X variants use 8b/10b PCS encoding. Initially, half-duplex mode was included in the standard but has since been abandoned.[14] Very few devices support gigabit speed in half-duplex.

Name Standard (Clause) Common connectors Description
Twisted-pair cable
1000BASE-T 802.3ab-1999 (40) 8P8C (IEC 60603-7) PAM-5 coded signaling, at least Category 5 cable, with Category 5e strongly recommended copper cabling with four twisted pairs. Each pair is used in both directions simultaneously. Extremely wide adoption.
1000BASE-T1 802.3bp-2016 (97) none specified uses a single, bi-directional twisted pair in full duplex mode only; cables specified for a reach of 15 m (automotive link segment) or 40 m (optional link segment), intended for automotive and industrial applications; it uses 80B/81B encoding in the PCS, PAM-3 signalling at 750 MBd (three bits transmitted as two ternary symbols) and includes Reed–Solomon error correction.
1000BASE-TX TIA-854 (2001) 8P8C (IEC 60603-7) Category 6 cable required. Unimplemented, withdrawn.
Fiber-optic cable
1000BASE-SX 802.3z-1998 (38) ST, SC, LC 8B10B NRZ coded signaling on 850 nm carrier, short-range multi-mode fiber (up to 550 m).
1000BASE-LX 802.3z-1998 (38) SC, LC 8B10B NRZ coded signaling on 1310 nm carrier, multi-mode fiber (up to 550 m) or single-mode fiber of up to 5 km; most current implementations are actually 1000BASE-LX10 with 10 km reach
1000BASE-BX10 802.3ah-2004 (59) SC, LC up to 10 km on 1490 and 1390 nm carriers; bidirectional over single strand of single-mode fiber; often called just 1000BASE-BX
1000BASE-LX10 802.3ah-2004 (59) SC, LC identical to 1000BASE-LX but increased power and sensitivity for up to 10 km over a pair of single-mode fiber; commonly called just 1000BASE-LX or, prior to 802.3ah, 1000BASE-LH; vendor-specific extensions exist for up to 40 km reach
1000BASE‑PX10‑D 802.3ah-2004 (60) SC, LC downstream (from head-end to tail-ends) over single-mode fiber using point-to-multipoint topology (supports at least 10 km).
1000BASE‑PX10‑U 802.3ah-2004 (60) upstream (from a tail-end to the head-end) over single-mode fiber using point-to-multipoint topology (supports at least 10 km).
1000BASE‑PX20‑D 802.3ah-2004 (60) downstream (from head-end to tail-ends) over single-mode fiber using point-to-multipoint topology (supports at least 20 km).
1000BASE‑PX20‑U 802.3ah-2004 (60) upstream (from a tail-end to the head-end) over single-mode fiber using point-to-multipoint topology (supports at least 20 km).
1000BASE-EX
1000BASE-ZX		 multi-vendor SC, LC up to 40 or 100 km over single-mode fiber on 1550 nm carrier[15]
Other
SFP INF-8074i (2001) SFP not a complete PHY in its own right but highly popular for adding modular transceivers; single lane, usually 1.25 Gbit/s
1000BASE-CX 802.3z-1998 (39) DE-9, FC style-2/IEC 61076-3-103, CX4/SFF-8470 8B10B NRZ coded signaling over up to 25 m shielded, balanced copper cable (150 Ω). Predates 1000BASE-T and is rarely used.
1000BASE‑KX 802.3ap-2007 (70) 1 m over backplane
1000BASE-RHx 802.3bv-2017 (115) RHA: clamping fixture
RHB/RHC: none specified		 1000BASE-RHA, -RHB, -RHC run over up to 50, 40, and 15 m of duplex plastic optical fiber (POF) using ~650 nm wavelength, 64b/65b encoding, and PAM16 symbols at 325 MBd; intended for home, industrial and automotive use, respectively

2.5 and 5 Gbit/s
Main article: 2.5GBASE-T and 5GBASE-T

2.5GBASE-T and 5GBASE-T are scaled-down variants of 10GBASE-T. These physical layers support twisted pair copper cabling only.

Name Standard (Clause) Common connectors Description
Twisted-pair cable
2.5GBASE-T802.3bz-2016 (126)8P8C – IEC 60603-7-4 (unscreened) or IEC 60603-7-5 (screened)100 m of Cat 5e
5GBASE-T100 m of Cat 6
Other
2.5GBASE-KX802.3cb-2018 (128)2.5 Gbit/s over 1 m of backplane, upscaled 1000BASE-KX
5GBASE-KR802.3cb-2018 (130)5 Gbit/s over 1 m of backplane, downscaled 10GBASE-KR

10 Gbit/s
Main article: 10 Gigabit Ethernet

10 Gigabit Ethernet defines a version of Ethernet with a nominal data rate of 10 Gbit/s, ten times as fast as Gigabit Ethernet. In 2002, the first 10 Gigabit Ethernet standard was published as IEEE Std 802.3ae-2002. Subsequent standards encompass media types for single-mode fiber (long haul), multi-mode fiber (up to 400 m), copper backplane (up to 1 m) and copper twisted pair (up to 100 m). All 10-gigabit standards were consolidated into IEEE Std 802.3-2008. Most 10-gigabit variants use 64b/66b PCS code (-R). As of 2009, 10 Gigabit Ethernet is predominantly deployed in carrier networks, where 10GBASE-LR and 10GBASE-ER enjoy significant market shares.

Name Standard (Clause) Common connectors Description
Twisted-pair cable
10GBASE-T 802.3an-2006 (55) 8P8C (IEC 60603-7-4 (unscreened) or IEC 60603-7-5 (screened)) Uses Cat 6A twisted-pair wiring, four lanes at 800 MBd each, PAM-16 with "DSQ128" line code
Fiber-optical cable
10GBASE-SR 802.3ae-2002 (49&52) SC, LC designed to support short distances over deployed multi-mode fiber cabling, it has a range of between 26 m and 400 m depending on cable type (modal bandwidth:reach: 160 MHz·km:26 m, 200 MHz·km:33 m, 400 MHz·km:66 m, 500 MHz·km:82 m, 2000 MHz·km:300 m, 4700 MHz·km:400 m)[16] using 850 nm wavelength
10GBASE-LX4 802.3ae-2002 (48&53) SC, LC uses four 8b/10b lanes with wavelength division multiplexing (1275, 1300, 1325, and 1350 nm) over deployed multi-mode cabling to support ranges of between 240 m and 300 m (400/500 MHz·km modal bandwidth). Also supports 10 km over single-mode fiber.
10GBASE-LR 802.3ae-2002 (49&52) SC, LC supports 10 km over single-mode fiber using 1,310 nm wavelength
10GBASE-ER 802.3ae-2002 (49&52) SC, LC supports 30 km over single-mode fiber using 1,550 nm wavelength (40 km over engineered links)
10GBASE-ZR - SC, LC offered by various vendors; supports 80 km or more over single-mode fiber using 1,550 nm wavelength
10GBASE-SW 802.3ae-2002 (50&52) A variation of 10GBASE-SR with 9.58464 Gbit/s, designed to be mapped directly as OC-192 / STM-64 SONET/SDH streams (850 nm wavelength)
10GBASE-LW 802.3ae-2002 (50&52) A variation of 10GBASE-LR with 9.58464 Gbit/s, designed to be mapped directly OC-192 / STM-64 SONET/SDH streams (1,310 nm wavelength)
10GBASE-EW 802.3ae-2002 (50&52) A variation of 10GBASE-ER with 9.58464 Gbit/s, designed to be mapped directly OC-192 / STM-64 SONET/SDH streams (1,550 nm wavelength)
10GBASE-LRM 802.3aq-2006 (49&68) SC, LC Extend to 220 m over deployed 500 MHz·km multi-mode fiber (1,310 nm wavelength)
10GBASE-BR - SC, LC offered by various vendors; bidirectional over a single strand of single-mode fiber for up to 10 to 80 km using (mostly) 1270 and 1330 nm wavelengths; often called "10GBASE-BX" or "BiDi"
Other
10GBASE-CX4 802.3ak-2004 (48&54) CX4/SFF-8470/IEC 61076-3-113 Designed to support short distances over copper cabling, it uses InfiniBand 4x connectors and CX4 twinaxial cabling and allows a cable length of up to 15 m. Was specified in IEEE 802.3ak-2004 which has been incorporated into IEEE 802.3-2008. Shipping has all but stopped in favor of 10GBASE-T and SFP+ DACs.
10GBASE-KX4 802.3ap-2007 (48&71) 1 m over 4 lanes of backplane
10GBASE-KR 802.3ap-2007 (49&72) 1 m over a single lane of backplane
10GPASS-XR802.3bn-2016 (100–102)EPON Protocol over Coax (EPoC) – up to 10 Gbit/s downstream and 1.6 Gbit/s upstream for a passive optical, point-to-multipoint network using passband OFDM with up to 16384-QAM
SFP+ (Direct Attach) SFF-8431 (2009) SFP+ highly popular for adding modular transceivers; used back-to-back as Direct Attach is also very popular for up to 7 m using passive twinaxial cables, up to 15 m using active cables, or up to 100 m using active optical cables (AOC); single lane, usually 10.3125 Gbit/s

25 Gbit/s
Main article: 25 Gigabit Ethernet

Single-lane 25-gigabit Ethernet is based on one 25.78125 GBd lane of the four from the 100 Gigabit Ethernet standard developed by task force P802.3by.[17] 25GBASE-T over twisted pair was approved alongside 40GBASE-T within IEEE 802.3bq.[18][19]

Name Standard (Clause) Common connectors Description
Twisted-pair cable
25GBASE-T 802.3bq-2016 (113) 8P8C (IEC 60603-7-51 and IEC 60603-7-81, 2000 MHz) scaled-down version of 40GBASE-T – up to 30 m Category 8 or ISO/IEC TR 11801-9905 [B1] cabling
Fiber-optical cable
25GBASE-SR 802.3by-2016 (112) LC, SC 850 nm over multi-mode cabling with 100 m (OM4) or 70 m (OM3) reach
25GBASE-LR 802.3cc-2017 (114) LC, SC 1310 nm over single-mode cabling with 10 km reach
25GBASE-ER 802.3cc-2017 (114) LC, SC 1550 nm over single-mode cabling with 30 km reach (40 km over engineered links)
Other
25GBASE-CR/CR-S 802.3by-2016 (110) SFP28 (SFF-8402/SFF-8432) direct-attach cable (DAC) over twinaxial cabling with 3 m (-CR-S) and 5 m (-CR-L) reach
25GBASE-KR/KR-S 802.3by-2016 (111) for printed-circuit backplane, derived from 100GBASE-KR4
SFP28 SFF-8402 (2014) SFP28 popular for adding modular transceivers

40 Gbit/s
Main article: 100 Gigabit Ethernet

This class of Ethernet was standardized in June 2010 as IEEE 802.3ba along with the first 100 Gbit/s generation, with an addition in March 2011 as IEEE 802.3bg,[20][21] and the fastest yet twisted-pair standard in IEEE 802.3bq-2016. The nomenclature is as follows:[22]

Name Standard (Clause) Common connectors Description
Twisted-pair cable
40GBASE-T 802.3bq-2016 (113) 8P8C (IEC 60603-7-51 and IEC 60603-7-81, 2000 MHz) requires Category 8 cabling, up to 30 m
Fiber-optical cable
40GBASE-SR4 802.3ba-2010 (86) MPO at least 100 m over 2000 MHz·km multi-mode fiber (OM3)
at least 150 m over 4700 MHz·km multi-mode fiber (OM4)
40GBASE-LR4 802.3ba-2010 (87) SC, LC at least 10 km over single-mode fiber, CWDM with 4 lanes using 1270, 1290, 1310 and 1330 nm wavelength
40GBASE-ER4 802.3ba-2010 (87) SC, LC at least 30 km over single-mode fiber, CWDM with 4 lanes using 1270, 1290, 1310 and 1330 nm wavelength (40 km over engineered links)
40GBASE-FR 802.3bg-2011 (89) SC, LC single lane, single-mode fiber over 2 km, 1550 nm wavelength
Other
40GBASE-KR4 802.3ba-2010 (84) at least 1 m over a backplane
40GBASE-CR4 802.3ba-2010 (85) QSFP+ (SFF-8436) up to 7 m over twinaxial copper cable assembly (4 lanes, 10 Gbit/s each)

50 Gbit/s

The IEEE 802.3cd Task Force has developed 50 Gbit/s along with next-generation 100 and 200 Gbit/s standards using 50 Gbit/s lanes-[23]

Name Standard (Clause) Common connectors Description
Fiber-optical cable
50GBASE-SR 802.3cd-2018 (138) LC, SC over OM4 multi-mode fiber using PAM-4 with 100 m reach, 70 m over OM3
50GBASE-FR 802.3cd-2018 (139) LC, SC over single-mode fiber using PAM-4 with 2 km reach
50GBASE-LR 802.3cd-2018 (139) LC, SC over single-mode fiber using PAM-4 with 10 km reach
Other
50GBASE-CR 802.3cd-2018 (136) SFP28, QSFP28, microQSFP, QSFP-DD, OSFP over twinaxial cable with 3 m reach
50GBASE-KR 802.3cd-2018 (137) over printed-circuit backplane, consistent with 802.3bs Clause 124

100 Gbit/s
Main article: 100 Gigabit Ethernet

The first generation of 100G Ethernet using 10 and 25 Gbit/s lanes was standardized in June 2010 as IEEE 802.3ba alongside 40 Gbit/s.[20] The second generation using 50 Gbit/s lanes has been developed by the IEEE 802.3cd Task Force along with 50 and 200 Gbit/s standards.[23] The third generation using a single 100 Gbit/s lane is currently being developed by the IEEE 802.3ck Task Force along with 200 and 400 Gbit/s PHYs and attachment unit interfaces (AUI) using 100 Gbit/s lanes.[24]

Name Standard (Clause) Common connectors Description
Fiber-optical cable
100GBASE-SR10 802.3ba-2010 (86) MPO at least 100 m over 2000 MHz·km multi-mode fiber (OM3)
at least 150 m over 4700 MHz·km multi-mode fiber (OM4)
100GBASE-SR4 802.3bm-2015 (95) MPO 4 lanes, at least 70 m over 2000 MHz·km multi-mode fiber (OM3)
at least 100 m over 4700 MHz·km multi-mode fiber (OM4)
100GBASE-SR2 802.3cd-2018 (138) MPO two 50 Gbit/s lanes using PAM-4 over OM4 multi-mode fiber with 100 m reach, 70 m over OM3
100GBASE-LR4 802.3ba-2010 (88) SC, LC at least 10 km over single-mode fiber, DWDM with 4 lanes using 1296, 1300, 1305 and 1310 nm wavelength
100GBASE-ER4 802.3ba-2010 (88) SC, LC at least 30 km over single-mode fiber, DWDM with 4 lanes using 1296, 1300, 1305 and 1310 nm wavelength (40 km over engineered links)
100GBASE-DR 802.3cu (140) LC, SC at least 500 m over single-mode fiber using a single lane
100GBASE-FR at least 2 km over single-mode fiber using a single lane
100GBASE-LR at least 10 km over single-mode fiber using a single lane
Other
100GBASE-CR10 802.3ba-2010 (85) CXP10 (SFF-8642) up to 7 m over twinaxial copper cable assembly (10 lanes, 10 Gbit/s each)
100GBASE-CR4 802.3bj-2014 (92) QSFP28 4X (SFF-8665) up to 5 m over twinaxial copper cable assembly (4 lanes, 25 Gbit/s each)
100GBASE-CR2 802.3cd-2018 (136) QSFP28, microQSFP, QSFP-DD, OSFP over twinaxial cable with 3 m reach (two 50 Gbit/s lanes)
100GBASE-CR 802.3ck (tbd) single-lane over twin-axial copper with at least 2 m reach
100GBASE-KR4 802.3bj-2014 (93) four lanes 25 Gbit/s each over a backplane
100GBASE-KR2 802.3cd-2018 (137) two 50 Gbit/s lanes over printed-circuit backplane, consistent with 802.3bs Clause 124
100GBASE-KR 802.3ck (tbd) single-lane over electrical backplanes supporting an insertion loss of up to 28 dB at 26.5625 GBd
100GBASE-KP4 802.3bj-2014 (94) using PAM4 modulation on four lanes 12.5 GBd each over a backplane

200 Gbit/s

First generation 200 Gbit/s have been defined by the IEEE 802.3bs Task Force and standardized in 802.3bs-2017.[25] The IEEE 802.3cd Task Force has developed 50 and next-generation 100 and 200 Gbit/s standards using one, two, or four 50 Gbit/s lanes respectively.[23] The next generation using 100 Gbit/s lanes is currently being developed by the IEEE 802.3ck Task Force along with 100 and 400 Gbit/s PHYs and attachment unit interfaces (AUI) using 100 Gbit/s lanes.[24]

Name Standard (Clause) Common connectors Description
Fiber-optical cable
200GBASE-DR4 802.3bs-2017 (121) MPO four PAM-4 lanes (26.5625 GBd) using individual strands of single-mode fiber with 500 m reach (1310 nm)
200GBASE-FR4 802.3bs-2017 (122) SC, LC four PAM-4 lanes (26.5625 GBd) using four wavelengths (CWDM) over single-mode fiber with 2 km reach (1270/1290/1310/1330 nm)
200GBASE-LR4 802.3bs-2017 (122) SC, LC four PAM-4 lanes (26.5625 GBd) using four wavelengths (DWDM) over single-mode fiber with 10 km reach (1296/1300/1305/1309 nm)
200GBASE-SR4 802.3cd-2018 (138) MPO four PAM-4 lanes over OM4 multi-mode fiber with 100 m reach, 70 m over OM3
200GBASE-ER4 802.3cn-2019 (tba) four-lane using four wavelengths over single-mode fiber with 40 km reach
Other
200GBASE-CR4 802.3cd-2018 (136) QSFP28, microQSFP, QSFP-DD, OSFP four-lane over twinaxial cable with 3 m reach
200GBASE-KR4 802.3cd-2018 (137) four-lane over printed-circuit backplane, consistent with 802.3bs Clause 124
200GBASE-KR2 802.3ck (tbd) two-lane over electrical backplanes supporting an insertion loss of up to 28 dB at 26.56 GBd
200GBASE-CR2 two-lane over twin-axial copper with at least 2 m reach

400 Gbit/s
Main article: Terabit Ethernet

The Institute of Electrical and Electronics Engineers (IEEE) has defined a new Ethernet standard capable of 200 and 400 Gbit/s in IEEE 802.3bs-2017.[25] 1 Tbit/s may be a further goal.[26]

In May 2018, IEEE 802.3 started the 802.3ck Task Force to develop standards for 100, 200, and 400 Gbit/s PHYs and attachment unit interfaces (AUI) using 100 Gbit/s lanes.[24]

In 2008, Robert Metcalfe, one of the co-inventors of Ethernet, said he believed commercial applications using Terabit Ethernet may occur by 2015, though it might require new Ethernet standards.[27] It was predicted this would be followed rapidly by a scaling to 100 Terabit, possibly as early as 2020. It is worth noting that these were theoretical predictions of technological ability, rather than estimates of when such speeds would actually become available at a practical price point.[28]

Name Standard (Clause) Common connectors Description
Fiber-optical cable
400GBASE-SR16 802.3bs-2017 (123) MPO sixteen lanes (26.5625 Gbit/s) using individual strands of OM4/OM5 multi-mode fiber with 100 m reach or 70 m over OM3
400GBASE-DR4 802.3bs-2017 (124) MPO four PAM-4 lanes (53.125 GBd) using individual strands of single-mode fiber with 500 m reach (1310 nm)
400GBASE-FR8 802.3bs-2017 (122) SC, LC eight PAM-4 lanes (26.5625 GBd) using eight wavelengths (CWDM) over single-mode fiber with 2 km reach
400GBASE-LR8 802.3bs-2017 (122) SC, LC eight PAM-4 lanes (26.5625 GBd) using eight wavelengths (DWDM) over single-mode fiber with 10 km reach
400GBASE-FR4 802.3cu SC, LC four lanes/wavelengths (CWDM, 1271/1291/1311/1331 nm) over single-mode fiber with 2 km reach
400GBASE-LR4 four lanes over single-mode fiber with 10 km reach
400GBASE-SR8 802.3cm-2020 SC, LC eight-lane using individual strands of multi-mode fiber with 100 m reach
400GBASE-SR4.2 four-lane using individual strands of multi-mode fiber with 100 m reach
400GBASE-ER8 802.3cn-2019 (tba) SC, LC eight-lane using eight wavelengths over single-mode fiber with 40 km reach
Other
400GBASE-KR4 802.3ck (tbd) four-lane over electrical backplanes supporting an insertion loss of up to 28 dB at 26.56 GBd
400GBASE-CR4 four-lane over twin-axial copper with at least 2 m reach

First mile
Main article: Ethernet in the first mile

For providing Internet access service directly from providers to homes and small businesses:

Name Standard (Clause) Description
10BaseS Proprietary[29] Ethernet over VDSL, used in Long Reach Ethernet products[30]; uses passband instead of the indicated baseband
2BASE-TL 802.3ah-2004 (61&63) Over telephone wires
10PASS-TS 802.3ah-2004 (61&62)
100BASE-LX10 802.3ah-2004 (58) Single-mode fiber-optics
100BASE-BX10
1000BASE-LX10 802.3ah-2004 (59)
1000BASE-BX10
1000BASE-PX10 802.3ah-2004 (60) Passive optical network
1000BASE-PX20
10GBASE-PR
10/1GBASE-PRX		 802.3av-2009 (75) 10 Gbit/s passive optical network with 1 or 10 Gbit/s uplink for 10 or 20 km range

Sublayers

Starting with Fast Ethernet, the physical layer specifications are divided into three sublayers in order to simplify design and interoperability:[31]

  • PCS (Physical Coding Sublayer) - This sublayer performs auto-negotiation and basic encoding such as 8b/10b, lane separation and recombination. For Ethernet, the bit rate at the top of the PCS is the nominal bit rate, e.g. 10 Mbit/s for classic Ethernet or 1000 Mbit/s for Gigabit Ethernet.
  • PMA (Physical Medium Attachment sublayer) - This sublayer performs PMA framing, octet synchronization/detection, and polynomial scrambling/descrambling.
  • PMD (Physical Medium Dependent sublayer) - This sublayer consists of a transceiver for the physical medium.

Twisted-pair cable
Main article: Ethernet over twisted pair

Several varieties of Ethernet were specifically designed to run over 4-pair copper structured cabling already installed in many locations.

In a departure from both 10BASE-T and 100BASE-TX, 1000BASE-T and above use all four cable pairs for simultaneous transmission in both directions through the use of echo cancellation.

Using point-to-point copper cabling provides the opportunity to transmit low electrical power along with the data. This is called Power over Ethernet and there are several, incremental IEEE 802.3 standards. Combining 10BASE-T (or 100BASE-TX) with "Mode A" allows a hub or a switch to transmit both power and data over only two pairs. This was designed to leave the other two pairs free for analog telephone signals.[32] The pins used in "Mode B" supply power over the "spare" pairs not used by 10BASE-T and 100BASE-TX. "4PPoE" defined in IEEE 802.3bt can use all four pairs to supply up to 100 W.

8P8C wiring (MDI)
PinPairColor telephone10BASE-T[33]
100BASE-TX[34]		1000BASE-T[35]
onwards		PoE mode APoE mode B
13 white/green TX+BI_DA+48 V out
23 green TX−BI_DA–48 V out
32 white/orange RX+BI_DB+48 V return
41 blue ringunusedBI_DC+48 V out
51 white/blue tipunusedBI_DC–48 V out
62 orange RX−BI_DB–48 V return
74 white/brown unusedBI_DD+48 V return
84 brown unusedBI_DD–48 V return

The cable requirements depend on the transmission speed and the employed encoding method. Generally, faster speeds require both higher-grade cables and more sophisticated encoding.

Minimum cable lengths

Fiber connections have minimum cable lengths due to level requirements on received signals.[36] Fiber ports designed for long-haul wavelengths require a signal attenuator if used within a building.

10BASE2 installations, running on RG-58 coaxial cable, require a minimum of 0.5 m between stations tapped into the network cable, this is to minimize reflections.[37]

10BASE-T, 100BASE-T, and 1000BASE-T installations running on twisted pair cable use a star topology. No minimum cable length is required for these networks.[38][39]

Some networking standards are not part of the IEEE 802.3 Ethernet standard, but support the Ethernet frame format, and are capable of interoperating with it.

  • LattisNet—A SynOptics pre-standard twisted-pair 10 Mbit/s variant.
  • 100BaseVG—An early contender for 100 Mbit/s Ethernet. It runs over Category 3 cabling. Uses four pairs. Commercial failure.
  • TIA 100BASE-SX—Promoted by the Telecommunications Industry Association. 100BASE-SX is an alternative implementation of 100 Mbit/s Ethernet over fiber; it is incompatible with the official 100BASE-FX standard. Its main feature is interoperability with 10BASE-FL, supporting autonegotiation between 10 Mbit/s and 100 Mbit/s operation – a feature lacking in the official standards due to the use of differing LED wavelengths. It is targeted at the installed base of 10 Mbit/s fiber network installations.
  • TIA 1000BASE-TX—Promoted by the Telecommunications Industry Association, it was a commercial failure, and no products exist. 1000BASE-TX uses a simpler protocol than the official 1000BASE-T standard so the electronics can be cheaper, but requires Category 6 cabling.
  • G.hn—A standard developed by ITU-T and promoted by HomeGrid Forum for high-speed (up to 1 Gbit/s) local area networks over existing home wiring (coaxial cables, power lines and phone lines). G.hn defines an Application Protocol Convergence (APC) layer that accepts Ethernet frames and encapsulates them into G.hn MSDUs.

Other networking standards do not use the Ethernet frame format but can still be connected to Ethernet using MAC-based bridging.

Other special-purpose physical layers include Avionics Full-Duplex Switched Ethernet and TTEthernet — Time-Triggered Ethernet for embedded systems.

References
  1. "Configuring and Troubleshooting Ethernet 10/100/1000Mb Half/Full Duplex Auto-Negotiation". Cisco Systems. Retrieved 2016-08-09. ...it is possible for a link partner to detect the speed at which the other link partner operates, even though the other link partner is not configured for auto-negotiation. In order to detect the speed, the link partner senses the type of electrical signal that arrives and sees if it is 10 Mb or 100 Mb.
  2. "Characteristics of 10GBASE-T Technology". fiber-optical-networking.com. 2017-11-08. Retrieved 2018-04-09.
  3. "Consideration for 40 Gigabit Ethernet" (PDF). IEEE HSSG. May 2007.
  4. "40 gigabit Ethernet answers" (PDF). IEEE HSSG. May 2007.
  5. "HECTO: High-Speed Electro-Optical Components for Integrated Transmitter and Receiver in Optical Communication". Hecto.eu. Retrieved December 17, 2011.
  6. "IEEE P802.3ba 40Gb/s and 100Gb/s Ethernet Task Force". IEEE. 2010-06-19.
  7. 802.3bs-2017 - IEEE Standard for Ethernet - Amendment 10: Media Access Control Parameters, Physical Layers, and Management Parameters for 200 Gb/s and 400 Gb/s Operation. IEEE 802.3. 2017-12-12. doi:10.1109/IEEESTD.2017.8207825. ISBN 978-1-5044-4450-7.
  8. IEEE 802.3 1.2.3 Physical layer and media notation
  9. John F. Shoch; Yogen K. Dalal; David D. Redell; Ronald C. Crane (August 1982). "Evolution of the Ethernet Local Computer Network" (PDF). IEEE Computer. 15 (8): 14–26. doi:10.1109/MC.1982.1654107.
  10. "L-com Introduces Commercial-Grade Thinnet (10Base-2) and Thicknet (10Base-5) Converters for Legacy Installs". Virtual-Strategy Magazine. 2012-06-11. Archived from the original on 2013-12-19. Retrieved 2012-07-01.
  11. IEEE 802.3 11.5.3 Delay requirements
  12. Zimmerman, Joann; Spurgeon, Charles (2014). Ethernet: The Definitive Guide, 2nd Edition. O'Reilly Media, Inc. ISBN 978-1-4493-6184-6. Retrieved 28 February 2016. This media system allowed multiple half-duplex Ethernet signal repeaters to be linked in series, exceeding the limit on the total number of repeaters that could be used in a given 10 Mb/s Ethernet system.... For the first few years after the standard was developed, equipment was available from a few vendors, but this equipment is no longer sold.
  13. IEEE 802.3 66. Extensions of the 10 Gb/s Reconciliation Sublayer (RS), 100BASE-X PHY, and 1000BASE-X PHY for unidirectional transport
  14. IEEE 802.3 41. Repeater for 1000 Mb/s baseband networks
  15. "Cisco Gigabit Ethernet Solutions for Cisco 7x00 Series Routers". Retrieved 17 February 2008.
  16. IEEE 802.3 Table 52-6 10GBASE-S operating range for each optical fiber type
  17. IEEE 802.3by 25 Gb/s Ethernet Task Force
  18. "IEEE P802.3bq 25G/40GBASE-T Task Force". Retrieved 2016-02-08.
  19. "Approval of IEEE Std 802.3by-2016, IEEE Std 802.3bq-2016, IEEE Std 802.3bp-2016 and IEEE Std 802.3br-2016". IEEE. 2016-06-30.
  20. Reimer, Jeremy (July 25, 2007). "New Ethernet standard: not 40Gbps, not 100, but both". Ars Technica. Retrieved December 17, 2011.
  21. "IEEE P802.3bg 40Gb/s Ethernet: Single-mode Fibre PMD Task Force". official task force web site. IEEE 802. April 12, 2011. Retrieved June 17, 2011.
  22. Ilango Ganga (May 13, 2009). "Chief Editor's Report" (PDF). IEEE P802.3ba 40Gb/s and 100Gb/s Ethernet Task Force public record. p. 8. Retrieved June 7, 2011.
  23. "IEEE 802.3 50 Gb/s, 100 Gb/s, and 200 Gb/s Ethernet Task Force". IEEE 802.3. 2016-05-17. Retrieved 2016-05-25.
  24. http://www.ieee802.org/3/ck/
  25. "[STDS-802-3-400G] IEEE P802.3bs Approved!". IEEE 802.3bs Task Force. Retrieved 2017-12-14.
  26. Snyder, Bob. "IEEE Begins Work on New Ethernet Standard". Retrieved 9 August 2016.
  27. "Bob Metcalfe on the Terabit Ethernet". Light Reading. February 15, 2008. Retrieved August 27, 2013.
  28. author. "IEEE to introduce new Ethernet speed, up to 1Tb per second - MacNN". Retrieved 9 August 2016.
  29. "Infineon Strengthens Leadership in MDU/MTU Market with Ethernet over VDSL Technology Patent Award". News release. Infineon Technologies AG. January 8, 2001. Archived from the original on April 13, 2001. Retrieved August 27, 2011.
  30. "Infineon Announces Second Quarter Results". News release. Infineon Technologies. April 24, 2001. Retrieved August 28, 2011. ...strategic design-win with Cisco for new long range Ethernet products incorporating Infineon's 10BaseS technology
  31. IEEE 802.3 Figure 1–1—IEEE 802.3 standard relationship to the ISO/IEC Open Systems Interconnection (OSI) reference model
  32. "Tech Info - LAN and Telephones". Zytrax.com. Retrieved December 17, 2011.
  33. IEEE 802.3 14.5.1 MDI connectors
  34. IEEE 802.3 Table 25–2—Twisted-pair MDI contact assignments
  35. IEEE 802.3 40.8.1 MDI connectors
  36. "Cisco 100BASE-FX SFP Fast Ethernet Interface Converter on Gigabit SFP Ports". Cisco Systems. Archived from the original on 2007-10-13.
  37. "IEEE Standard for Ethernet 802.3-2008 Clauses 10.7.2.1-2" (PDF).
  38. "Troubleshooting Ethernet Collisions". Retrieved 9 August 2016.
  39. Gigabit Ethernet (PDF), retrieved 2016-08-09
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