Power over Ethernet

Power over Ethernet or PoE describes any of several standard or ad-hoc systems which pass electric power along with data on twisted pair Ethernet cabling. This allows a single cable to provide both data connection and electric power to devices such as wireless access points, IP cameras, and VoIP phones.

There are several common techniques for transmitting power over Ethernet cabling. Three of them have been standardized by IEEE 802.3 since 2003. These standards are known as Alternative A, Alternative B, and 4PPoE. For 10BASE-T and 100BASE-TX, only two of the four signal pairs in typical Cat 5 cable are used. Alternative B separates the data and the power conductors, making troubleshooting easier. It also makes full use of all four twisted pairs in a typical Cat 5 cable. The positive voltage runs along pins 4 and 5, and the negative along pins 7 and 8.

Alternative A transports power on the same wires as data for 10 and 100 Mbit/s Ethernet variants. This is similar to the phantom power technique commonly used for powering condenser microphones. Power is transmitted on the data conductors by applying a common voltage to each pair. Because twisted-pair Ethernet uses differential signaling, this does not interfere with data transmission. The common-mode voltage is easily extracted using the center tap of the standard Ethernet pulse transformer. For Gigabit Ethernet and faster, all four pairs are used for data transmission, so both Alternatives A and B transport power on wire pairs also used for data.

4PPoE provides power using all four pairs of a twisted-pair cable. This enables higher power for applications like PTZ cameras, high-performance wireless access points, or even charging laptop batteries.

In addition to standardizing existing practice for spare-pair (Alternative B), common-mode data pair power (Alternative A) and 4-pair transmission (4PPoE), the IEEE PoE standards provide for signaling between the power sourcing equipment (PSE) and powered device (PD). This signaling allows the presence of a conformant device to be detected by the power source, and allows the device and source to negotiate the amount of power required or available.

ZyXEL ZyAIR G-1000 and D-Link DWL-P50 20060829 2
In this configuration, an Ethernet connection includes power over Ethernet (gray cable looping below), and a PoE splitter provides a separate data cable (gray, looping above) and power cable (black, also looping above) for a wireless access point. The splitter is the silver and black box in the middle between the wiring junction box (left) and the access point (right). The PoE connection eliminates the need for a nearby power outlet. In another common configuration, the access point or other connected device includes internal PoE splitting and the external splitter is not used.

Standards development

The original IEEE 802.3af-2003[1] PoE standard provides up to 15.4 W of DC power (minimum 44 V DC and 350 mA[2][3]) on each port.[4] Only 12.95 W is assured to be available at the powered device as some power dissipates in the cable.[5] The updated IEEE 802.3at-2009[6] PoE standard also known as PoE+ or PoE plus, provides up to 25.5 W of power for "Type 2" devices.[7] The 2009 standard prohibits a powered device from using all four pairs for power.[8] Both of these standards have since been incorporated into the IEEE 802.3-2012 publication.[9]

The IEEE 802.3bu-2016[10] amendment introduced single-pair Power over Data Lines (PoDL) for the single-pair Ethernet standards 100BASE-T1 and 1000BASE-T1 intended for automotive and industrial applications. On the two-pair or four-pair standards power is transmitted only between pairs, so that within each pair there is no voltage present other than that representing the transmitted data. With single-pair Ethernet, power is transmitted in parallel to the data. PoDL defines 10 power classes, ranging from .5 to 50 W (at PD).

Looking at ways of increasing the amount of power transmitted, IEEE has defined IEEE 802.3bt 4PPoE in September 2018.[11] The standard introduces two additional power types: up to 55 W (Type 3) and up to 90-100 W (Type 4). Each pair of twisted pairs needs to handle a current of up to 600 mA (Type 3) or 960 mA (Type 4).[12] Additionally, support for 2.5GBASE-T, 5GBASE-T and 10GBASE-T is included.[13] This development opens the door to new applications and expands the use of applications such as high-performance wireless access points and surveillance cameras.


IP camera Ethernet power

An IP camera powered by Power over Ethernet


Avaya IP Phone 1140E with PoE support


A CableFree FOR3 microwave link installed in the UAE: a full outdoor radio featuring proprietary high power over Ethernet

Examples of devices powered by PoE include:[14]


Power sourcing equipment

"Power sourcing equipment" (PSE) are devices that provide (source) power on the Ethernet cable. This device may be a network switch, commonly called an endspan (IEEE 802.3af refers to it as endpoint), or an intermediary device between a non-PoE-capable switch and a PoE device, an external PoE injector, called a midspan device.[17]

Powered device

A "Powered device" (PD) is any device powered by PoE, thus consuming energy. Examples include wireless access points, VoIP phones, and IP cameras.

Many powered devices have an auxiliary power connector for an optional external power supply. Depending on the design, some, none, or all of the device's power can be supplied from the auxiliary port,[18][19] with the auxiliary port also sometimes acting as backup power in case PoE-supplied power fails.

Power management features and integration

Avaya ERS 5500 switch with 48 Power over Ethernet ports

Advocates of PoE expect PoE to become a global long term DC power cabling standard and replace a multiplicity of individual AC adapters, which cannot be easily centrally managed.[20] Critics of this approach argue that PoE is inherently less efficient than AC power due to the lower voltage, and this is made worse by the thin conductors of Ethernet. Advocates of PoE, like the Ethernet Alliance, point out that quoted losses are for worst case scenarios in terms of cable quality, length and power consumption by powered devices.[21] In any case, where the central PoE supply replaces several dedicated AC circuits, transformers and inverters, the power loss in cabling can be justifiable.

Integrating EEE and PoE

After integration of PoE with the IEEE 802.3az Energy-Efficient Ethernet (EEE) standard potentially produces additional energy savings. Pre-standard integrations of EEE and PoE (such as Marvell's EEPoE outlined in a May 2011 white paper) claim to achieve a savings upwards of 3 W per link. This saving is especially significant as higher power devices come online. Marvell claims that:

"With the evolution of PoE from a fairly low power source (up to 12.95 W per port) to one with devices of up to 25.5 W, the direct current (DC) power losses over Ethernet cables increased exponentially. Approximately 4.5 W/port of power is wasted on a CAT5, CAT5e, CAT6 or CAT6A cable...after 100 m... EEE typically saves no more than 1 W per link, so addressing the 4.5 W per link loss from PoE transmission inefficiency would provide much more incremental savings. New energy-efficient PoE (EEPoE) technology can increase efficiency to 94% while transmitting over the same 25 ohm cable, powering IEEE 802.3at-compliant devices in synchronous 4-pairs. When utilizing synchronous 4-pairs, powered devices are fed using all the available wires. For example, on a 24-port IEEE 802.3at-2009 Type 2 system (delivering 25.5 W per port), more than 50 W are saved."[22]

Standard implementation

Standards-based Power over Ethernet is implemented following the specifications in IEEE 802.3af-2003 (which was later incorporated as clause 33 into IEEE 802.3-2005) or the 2009 update, IEEE 802.3at. The standards require category 5 cable or better for high power levels but allow using category 3 cable if less power is required.[23]

Power is supplied as a common-mode signal over two or more of the differential pairs of wires found in the Ethernet cables and comes from a power supply within a PoE-enabled networking device such as an Ethernet switch or can be injected into a cable run with a midspan power supply. A midspan power supply, also known as a PoE power injector, is an additional PoE power source that can be used in combination with a non-PoE switch.

A phantom power technique is used to allow the powered pairs to also carry data. This permits its use not only with 10BASE-T and 100BASE-TX, which use only two of the four pairs in the cable, but also with 1000BASE-T (gigabit Ethernet), 2.5GBASE-T, 5GBASE-T, and 10GBASE-T which use all four pairs for data transmission. This is possible because all versions of Ethernet over twisted pair cable specify differential data transmission over each pair with transformer coupling; the DC supply and load connections can be made to the transformer center-taps at each end. Each pair thus operates in common mode as one side of the DC supply, so two pairs are required to complete the circuit. The polarity of the DC supply may be inverted by crossover cables; the powered device must operate with either pair: spare pairs 4–5 and 7–8 or data pairs 1–2 and 3–6. Polarity is defined by the standards on data pairs, and ambiguously implemented for spare pairs, with the use of a diode bridge.

Comparison of PoE parameters
Property 802.3af (802.3at Type 1) "PoE" 802.3at Type 2 "PoE+" 802.3bt Type 3 "4PPoE"[24] 802.3bt Type 4
Power available at PD[note 1] 12.95 W 25.50 W 51 W 71 W
Maximum power delivered by PSE 15.40 W 30.0 W 60 W 100 W
Voltage range (at PSE) 44.0–57.0 V[25] 50.0–57.0 V[25] 50.0–57.0 V 52.0–57.0 V
Voltage range (at PD) 37.0–57.0 V[26] 42.5–57.0 V[26] 42.5–57.0 V[27] 41.1–57.0 V
Maximum current Imax 350 mA[28] 600 mA[28] 600 mA per pair[27] 960 mA per pair[27]
Maximum cable resistance per pairset 20 Ω[29] (Category 3) 12.5 Ω[29] (Category 5) 12.5 Ω[27] 12.5 Ω[27]
Power management Three power class levels (1-3) negotiated by signature Four power class level (1-4) negotiated by signature or 0.1 W steps negotiated by LLDP Six power class levels (1-6) negotiated by signature or 0.1 W steps negotiated by LLDP[30] Eight power class levels (1-8) negotiated by signature or 0.1 W steps negotiated by LLDP
Derating of maximum cable ambient operating temperature None 5 °C (9 °F) with one mode (two pairs) active 10 °C (20 °F) with more than half of bundled cables pairs at Imax[31] 10 °C (20 °F) with temperature planning required
Supported cabling Category 3 and Category 5[23] Category 5[23][note 2] Category 5 Category 5
Supported modes Mode A (endspan), Mode B (midspan) Mode A, mode B Mode A, mode B, 4-pair mode 4-pair mode


  1. ^ Most switched power supplies within the powered device will lose another 10 to 25% of the available power to heat.
  2. ^ More stringent cable specification allows assumption of more current carrying capacity and lower resistance (20.0 Ω for Category 3 versus 12.5 Ω for Category 5).

Powering devices

Three modes, A, B, and 4-pair are available. Mode A delivers power on the data pairs of 100BASE-TX or 10BASE-T. Mode B delivers power on the spare pairs. 4-pair delivers power on all four pairs. PoE can also be used on 1000BASE-T, 2.5GBASE-T, 5GBASE-T and 10GBASE-T Ethernet, in which case there are no spare pairs and all power is delivered using the phantom technique.

Mode A has two alternate configurations (MDI and MDI-X), using the same pairs but with different polarities. In mode A, pins 1 and 2 (pair #2 in T568B wiring) form one side of the 48 V DC, and pins 3 and 6 (pair #3 in T568B) form the other side. These are the same two pairs used for data transmission in 10BASE-T and 100BASE-TX, allowing the provision of both power and data over only two pairs in such networks. The free polarity allows PoE to accommodate for crossover cables, patch cables and Auto MDI-X.

In mode B, pins 4–5 (pair #1 in both T568A and T568B) form one side of the DC supply and pins 7–8 (pair #4 in both T568A and T568B) provide the return; these are the "spare" pairs in 10BASE-T and 100BASE-TX. Mode B, therefore, requires a 4-pair cable.

The PSE, not the PD, decides whether power mode A or B shall be used. PDs that implement only mode A or mode B are disallowed by the standard.[32] The PSE can implement mode A or B or both. A PD indicates that it is standards-compliant by placing a 25 kΩ resistor between the powered pairs. If the PSE detects a resistance that is too high or too low (including a short circuit), no power is applied. This protects devices that do not support PoE. An optional power class feature allows the PD to indicate its power requirements by changing the sense resistance at higher voltages.

To retain power, the PD must use at least 5–10 mA for at least 60 ms at a time. If the PD goes more than 400 ms without meeting this requirement, the PSE will consider the device disconnected and, for safety reasons, remove power.[33]

There are two types of PSEs: endspans and midspans. Endspans (commonly called PoE switches) are Ethernet switches that include the power over Ethernet transmission circuitry. Midspans are power injectors that stand between a regular Ethernet switch and the powered device, injecting power without affecting the data. Endspans are normally used on new installations or when the switch has to be replaced for other reasons (such as moving from 10/100 Mbit/s to 1 Gbit/s), which makes it convenient to add the PoE capability. Midspans are used when there is no desire to replace and configure a new Ethernet switch, and only PoE needs to be added to the network.

Stages of powering up a PoE link
Stage Action Volts specified
802.3af 802.3at
Detection PSE detects if the PD has the correct signature resistance of 19–26.5 kΩ 2.7–10.1
Classification PSE detects resistor indicating power range (see below) 14.5–20.5
Mark 1 Signals PSE is 802.3at capable. PD presents a 0.25–4 mA load. 7–10
Class 2 PSE outputs classification voltage again to indicate 802.3at capability 14.5–20.5
Mark 2 Signals PSE is 802.3at capable. PD presents a 0.25–4 mA load. 7–10
Startup Startup voltage[34][35] > 42 > 42
Normal operation Supply power to device[34][35] 37–57 42.5–57

IEEE 802.3at capable devices are also referred to as "type 2". An 802.3at PSE may also use layer2 communication to signal 802.3at capability.[36]

Power levels available[37]
Class Usage Classification current
Power range at PD per pair
Power from PSE per pair
Class description
0 Default 0–4 0.44–12.94 15.4 Classification unimplemented
1 Optional 9–12 0.44–3.84 4.00 Very Low power
2 Optional 17–20 3.84–6.49 7.00 Low power
3 Optional 26–30 6.49–12.95 15.4 Mid power
4 Valid for Type 2 (802.3at) devices,
not allowed for 802.3af devices
36–44 12.95–25.50 30 High power
5 Valid for Type 3 (802.3bt) devices 40 (2×35.6 @4-pair) 45
6 51 60
7 Valid for Type 4 (802.3bt) devices 62 (4-pair) 75
8 71.3 (4-pair) 99
8+ 99.9 (4-pair)

Class 4 can only be used by IEEE 802.3at (type 2) devices, requiring valid Class 2 and Mark 2 currents for the power up stages. An 802.3af device presenting a class 4 current is considered non-compliant and, instead, will be treated as a Class 0 device.[38]

Configuration via Ethernet layer 2 LLDP

LLDP Power Via MDI TLV IEEE 802.3-2015[39]
TLV Header TLV information string
(7 bits)
(9 bits)
IEEE 802.3 OUI  
(3 octets)
IEEE 802.3 subtype
(1 octet)
MDI power support[40]
(1 octet)
PSE power pair[40]
(1 octet)
Power class 
(1 octet)
Type/source priority 
(1 octet)
PD requested power value 
(2 octets)
PSE allocated power value 
(2 octets)
127 12 00-12-0F 2 b0 port class: 1=PSE; 0=PD
b1 PSE MDI power support
b2 PSE MDI power state
b3 PSE pairs control ability
b7-4 reserved
1=signal pair
2=spare pair
1=class 0
2=class 1
3=class 2
4=class 3
5=class 4
b7 power type: 1=type 1; 0=type 2
b6 power type: 1=PD; 0=PSE
b5-4: power source
b3-2: reserved
b0-1 power priority: 11=low;10=high;01=critical;00=unknown
0–25.5 W in 0.1 W steps 0–25.5 W in 0.1 W steps
Legacy LLDP Power via MDI TLV IEEE 802.1AB-2009[41]
TLV Header TLV information string
(7 bits)
(9 bits)
IEEE 802.3 OUI  
(3 octets)
IEEE 802.3 subtype
(1 octet)
MDI power support[40]
(1 octet)
PSE power pair[40]
(1 octet)
Power class 
(1 octet)
127 7 00-12-0F 2 b0 port class: 1=PSE; 0=PD
b1 PSE MDI power support
b2 PSE MDI power state
b3 PSE pairs control ability
b7-4 reserved
1=signal pair
2=spare pair
1=class 0
2=class 1
3=class 2
4=class 3
5=class 4
Legacy LLDP- MED Advanced Power Management[42]:8
TLV Header MED Header Extended power via MDI
(7 bits)
(9 bits)
(3 octets)
Extended power via MDI subtype 
(1 octet)
Power type 
(2 bits)
Power source 
(2 bits)
Power priority 
(4 bits)
Power value 
(2 octets)
127 7 00-12-BB 4 PSE or PD Normal or Backup conservation Critical,
0–102.3 W in 0.1 W steps

The setup phases are as follows:

  • PSE (provider) tests PD (consumer) physically using 802.3af phase class 3.
    • PSE powers up PD.
  • PD sends to PSE: I'm a PD, max power = X, max power requested = X.
  • PSE sends to PD: I'm a PSE, max power allowed = X.
    • PD may now use the amount of power as specified by the PSE.

The rules for this power negotiation are:

  • PD shall never request more power than physical 802.3af class
  • PD shall never draw more than max power advertised by PSE
  • PSE may deny any PD drawing more power than max allowed by PSE
  • PSE shall not reduce power allocated to PD that is in use
  • PSE may request reduced power, via conservation mode[42]:10

Non-standard implementations


Some Cisco manufactured WLAN access points and IP phones supporting a proprietary form of PoE many years before there was an IEEE standard for delivering PoE. Cisco's original PoE implementation is not software upgradeable to the IEEE 802.3af standard. Cisco's original PoE equipment is capable of delivering up to 10 W per port. The amount of power to be delivered is negotiated between the endpoint and the Cisco switch based on a power value that was added to the Cisco proprietary Cisco Discovery Protocol (CDP). CDP is also responsible for dynamically communicating the Voice VLAN value from the Cisco switch to the Cisco IP Phone.

Under Cisco's pre-standard scheme, the PSE (switch) will send a Fast Link Pulse (FLP) on the transmit pair. The PD (device) connects the transmit line to the receive line via a low pass filter. And thus the PSE gets the FLP in return. And a common mode current between pair 1 and 2 will be provided resulting in 48 V DC[43] and 6.3 W[44] default of allocated power. The PD has then to provide Ethernet link within 5 seconds to the auto-negotiation mode switch port. A later CDP message with a type-length-value tells the PSE its final power requirement. A discontinued link pulses shuts down power.[45]

In 2014, Cisco created another non-standard PoE implementation called Universal Power over Ethernet (UPOE). UPOE can use all 4 pairs, after negotiation, to supply up to 60 W.[46]

Linear Technology

A proprietary high-power development called LTPoE++ using a single CAT-5e Ethernet cable is capable of supplying varying levels at 38.7 W, 52.7 W, 70 W, and 90 W in addition to being backwards compatible with IEEE 802.3at.[47]


PowerDsine, acquired by Microsemi in 2007, has been selling midspan power injectors since 1999 with its proprietary Power over LAN solution. Several companies such as Polycom, 3Com, Lucent and Nortel utilize PowerDsine's Power over LAN.[48]


The common 100 Mbit/s passive applications use the pinout of 802.3af mode B - with DC plus on pins 4 and 5 and DC minus on 7 and 8 (see chart below) and data on 1-2 and 3-6. Gigabit passive injectors use a transformer on the data pins to allow power and data to share the cable and is typically compatible with 802.3af Mode A. In the common "passive" PoE system, the injector does not communicate with the powered device to negotiate its voltage or wattage requirements, but merely supplies power at all times. Passive midspan injectors up to 12 ports simplify installations.

Devices needing 5 Volts cannot typically use PoE at 5 V on Ethernet cable beyond short distances (about 15 feet (4.6 m)) as the voltage drop of the cable becomes too significant, so a 24 V or 48 V to 5 V DC-DC converter is required at the remote end.[49]

Passive PoE power sources are commonly used with a variety of indoor and outdoor wireless radio equipment, most commonly from Motorola (now Cambium), Ubiquiti, Mikrotik and others. Earlier versions of passive PoE 24VDC power sources shipped with 802.11a, 802.11g and 802.11n based radios are commonly 100 Mbit/s only. Specifications vary by manufacturer and model, but some of the common specifications include:

  • 24VDC 0.5A 100 Mbit/s or 1 Gbit/s
  • 24VDC 1.0A 100 Mbit/s or 1 Gbit/s
  • 48VDC 1.0A 100 Mbit/s or 1 Gbit/s
  • 56VDC 1.0A and 2.0A 1 Gbit/s (used for 45W+ load point to point microwave and millimeter band radios)

Passive DC-to-DC injectors also exist which convert a 9 V to 36 V DC, or 36 V to 72 V DC power source to a stabilized 24 V 1 A, 48 V 0.5 A, or up to 48V 2.0A PoE feed with '+' on pins 4 & 5 and '−' on pins 7 & 8. These DC-to-DC PoE injectors are used in various telecom applications.[50]

Power capacity limits

The ISO/IEC TR 29125 and Cenelec EN 50174-99-1 draft standards outline the cable bundle temperature rise that can be expected from the use of 4PPoE. A distinction is made between two scenarios: 1.) bundles heating up from the inside to the outside, and 2.) bundles heating up from the outside to match the ambient temperature. The second scenario largely depends on the way that the cable bundle has been installed, whereas the first is solely influenced by the physical make-up of the cable. In a standard U/UTP cable, the PoE-related temperature rise increases by a factor of 5. In a shielded cable, this value drops to between 2.5 and 3, depending on the design. Put another way, the temperature increases by twice as much in a U/UTP cable bundle than in a comparable bundle of S/FTP cables.


802.3af Standards A and B from the power sourcing equipment perspective
Pins at switch T568A color T568B color 10/100 mode B,
DC on spares
10/100 mode A,
mixed DC & data
1000 (1 gigabit) mode B,
DC & bi-data
1000 (1 gigabit) mode A,
DC & bi-data
Pin 1 Wire white green stripe
White/green stripe
Wire white orange stripe
White/orange stripe
Rx + Rx + DC + TxRx A + TxRx A + DC +
Pin 2 Wire green
Green solid
Wire orange
Orange solid
Rx − Rx − DC + TxRx A − TxRx A − DC +
Pin 3 Wire white orange stripe
White/orange stripe
Wire white green stripe
White/green stripe
Tx + Tx + DC − TxRx B + TxRx B + DC −
Pin 4 Wire blue
Blue solid
Wire blue
Blue solid
DC + Unused TxRx C + DC + TxRx C +
Pin 5 Wire white blue stripe
White/blue stripe
Wire white blue stripe
White/blue stripe
DC + Unused TxRx C − DC + TxRx C −
Pin 6 Wire orange
Orange solid
Wire green
Green solid
Tx − Tx − DC − TxRx B − TxRx B − DC −
Pin 7 Wire white brown stripe
White/brown stripe
Wire white brown stripe
White/brown stripe
DC − Unused TxRx D + DC − TxRx D +
Pin 8 Wire brown
Brown solid
Wire brown
Brown solid
DC − Unused TxRx D − DC − TxRx D −


  1. ^ 802.3af-2003, June 2003
  2. ^ IEEE 802.3-2005, section 2, table 33-5, item 1
  3. ^ IEEE 802.3-2005, section 2, table 33-5, item 4
  4. ^ IEEE 802.3-2005, section 2, table 33-5, item 14
  5. ^ IEEE 802.3-2005, section 2, clause
  6. ^ 802.3at Amendment 3: Data Terminal Equipment (DTE) Power via the Media Dependent Interface (MDI) Enhancements, September 11, 2009
  7. ^ "Amendment to IEEE 802.3 Standard Enhances Power Management and Increases Available Power". IEEE. Retrieved 2010-06-24.
  8. ^ Clause 33.3.1 stating, "PDs that simultaneously require power from both Mode A and Mode B are specifically not allowed by this standard."
  9. ^ IEEE 802.3-2012 Standard for Ethernet, IEEE Standards Association, December 28, 2012
  10. ^ "IEEE P802.3bu 1-Pair Power over Data Lines (PoDL) Task Force". 2017-03-17. Retrieved 2017-10-30.
  11. ^ "IEEE P802.3bt DTE Power via MDI over 4-Pair Task Force". 2016-03-29. Retrieved 2018-10-11.
  12. ^ IEEE 802.3bt 145.1.3 System parameters
  13. ^ "IEEE P802.3bt/D1.5 Draft Standard for Ethernet – Amendment: Physical Layer and Management Parameters for DTE Power via MDI over 4-Pair" (PDF). 30 November 2015. Retrieved 2017-04-09.
  14. ^ "Power over Ethernet". Commercial web page. GarrettCom. Archived from the original on August 29, 2011. Retrieved August 6, 2011.
  15. ^ "The Bright New Outlook For LEDs: New Drivers, New Possibilities" (PDF). Commercial Application Note. Maxim Integrated. Retrieved 27 April 2015.
  16. ^ "Ethernet Extender for POE and POE Plus equipment". Retrieved 2015-10-26.
  17. ^ Cisco Aironet technotes on 1000BASE-T mid-span devices, visited 18 July 2011
  18. ^ IEEE 802.3-2008, section 2, clause 33.3.5
  19. ^ IEEE 802.3at-2009, clause 33.3.7
  20. ^ Dave Dwelley (Oct 26, 2003), "Banish Those "Wall Warts" With Power Over Ethernet", Electronic Design, retrieved 2018-07-21
  21. ^ David Tremblay; Lennart Yseboodt (November 10, 2017), "Clarifying misperceptions about Power over Ethernet and cable losses", Cabling Installation and Maintenance, retrieved 2018-07-21
  22. ^ Roman Kleinerman; Daniel Feldman (May 2011), Power over Ethernet (PoE): An Energy-Efficient Alternative (PDF), Marvell, retrieved 2016-08-31
  23. ^ a b c IEEE 802.3at-2009, clause 33.1.1c
  24. ^ Koussalya Balasubramanian; David Abramson (May 2014). "Base Line Text for IEEE 802.3 BT" (PDF). Retrieved 2017-04-02.
  25. ^ a b IEEE 802.3at-2009 Table 33-11
  26. ^ a b IEEE 802.3at-2009 Table 33-18
  27. ^ a b c d e IEEE 802.3bt Table 145-1
  28. ^ a b IEEE 802.3at-2009 Table 33-1
  29. ^ a b IEEE 802.3at-2009 33.1.4 Type 1 and Type 2 system parameters
  30. ^ IEEE 802.3bt 145.3.1 PD Type definitions
  31. ^ IEEE 802.3bt Cabling requirements
  32. ^ IEEE 802.3 33.3.1 PD PI
  33. ^ Herbold, Jacob; Dwelley, Dave (27 October 2003), "Banish Those "Wall Warts" With Power Over Ethernet", Electronic Design, 51 (24): 61, archived from the original on 2005-03-20
  34. ^ a b IEEE 802.3-2008, section 2, table 33-12
  35. ^ a b IEEE 802.3at-2009, table 33-18
  36. ^ "LTC4278 IEEE 802.3at PD with Synchronous No-Opto Flyback Controller and 12V Aux Support" (PDF). 2010-01-11 cds.linear.com
  37. ^ IEEE 802.3-2005, section 2, table 33-3
  38. ^ IEEE 802.3-2008, section 2, clause 33.3.4
  39. ^ IEEE 802.3 Clause 79.3.2 Power Via MDI TLV
  40. ^ a b c d IETF RFC 3621
  41. ^ IEEE 802.1AB-2009 Annex F.3 Power Via MDI TLV
  42. ^ a b "LLDP / LLDP-MED Proposal for PoE Plus (2006-09-15)" (PDF).2010-01-10
  43. ^ "Planning for Cisco IP Telephony > Network Infrastructure Analysis". 2010-01-12 ciscopress.com
  44. ^ "Power over Ethernet on the Cisco Catalyst 6500 Series Switch" (PDF). Archived from the original (PDF) on 2010-11-06. 2010-01-12 conticomp.com
  45. ^ "Understanding the Cisco IP Phone 10/100 Ethernet In-Line Power Detection Algorithm - Cisco Systems". 2010-01-12 cisco.com
  46. ^ "Cisco Universal Power Over Ethernet - Unleash the Power of your Network White Paper". Cisco Systems. 2014-07-11. Archived from the original on 2017-11-28.
  47. ^ "Power over Ethernet Interface Controllers".
  48. ^ PowerDsine Limited, archived from the original on 2012-07-28
  49. ^ "Passive Power over Ethernet equipment, AC-DC and DC-DC". 2013-06-28 wifiqos.com
  50. ^ "Passive Power over Ethernet equipment, AC-DC and DC-DC". 2010-02-18 tyconpower.com

External links


IEEE 802.3bz, NBASE-T and MGBASE-T refer to efforts to produce a standard for Ethernet over twisted pair copper wire at speeds of 2.5 Gbit/s and 5 Gbit/s. This would create intermediate speeds between existing standards Gigabit Ethernet and 10 Gigabit Ethernet. The resulting standards are named 2.5GBASE-T and 5GBASE-T.

Backhaul (telecommunications)

In a hierarchical telecommunications network the backhaul portion of the network comprises the intermediate links between the core network, or backbone network, and the small subnetworks at the edge of the network.

In contracts pertaining to such networks, backhaul is the obligation to carry packets to and from that backbone network. A business definition of backhaul is the commercial wholesale bandwidth provider who offers quality of service (QOS) guarantees. It appears most often in telecommunications trade literature in this sense, whereby the backhaul connection is defined not technically but by who operates and manages it, and who takes legal responsibility for the connection or uptime.

In both the technical and commercial definitions, backhaul generally refers to the side of the network that communicates with the global Internet, paid for at wholesale commercial access rates to or at an Internet exchange point or other core network access location. Sometimes middle mile networks exist between the customer's own LAN and those exchanges. This can be a local WAN connection.

Cell phones communicating with a single cell tower constitute a local subnetwork; the connection between the cell tower and the rest of the world begins with a backhaul link to the core of the Internet service provider's network (via a point of presence). The term backhaul may be used to describe the entire wired part of a network, although some networks have wireless instead of wired backhaul, in whole or in part, for example using microwave bands and mesh network and edge network topologies that may use a high-capacity wireless channel to get packets to the microwave or fiber links.

A telephone company is very often the Internet Service Provider providing backhaul, although for academic Research and Education networks, large commercial networks or municipal networks, it is increasingly common to connect to public broadband backhaul. See national broadband plans from around the world, many of which were motivated by the perceived need to break the monopoly of incumbent commercial providers. The US plan for instance, specifies that all community anchor institutions should be connected by gigabit fiber optics before the end of 2020.

Category 3 cable

Category 3 cable, commonly known as Cat 3 or station wire, and less commonly known as VG or voice-grade (as, for example, in 100BaseVG), is an unshielded twisted pair (UTP) cable used in telephone wiring. It is part of a family of copper cabling standards defined jointly by the Electronic Industries Alliance (EIA) and the Telecommunications Industry Association (TIA) and published in TIA/EIA-568-B.

Although designed to reliably carry data up to 10 Mbit/s, modern data networks run at much higher speeds, and Cat 5e or Cat 6 is now used for all new installations.

Cisco Discovery Protocol

Cisco Discovery Protocol (CDP) is a proprietary Data Link Layer protocol developed by Cisco Systems. It is used to share information about other directly connected Cisco equipment, such as the operating system version and IP address. CDP can also be used for On-Demand Routing, which is a method of including routing information in CDP announcements so that dynamic routing protocols do not need to be used in simple networks.

Cisco devices send CDP announcements to the multicast destination address 01-00-0c-cc-cc-cc, out each connected network interface. These multicast frames may be received by Cisco switches and other networking devices that support CDP into their connected network interface. This multicast destination is also used in other Cisco protocols such as Virtual Local Area Network (VLAN) Trunking Protocol (VTP). By default, CDP announcements are sent every 60 seconds on interfaces that support Subnetwork Access Protocol (SNAP) headers, including Ethernet, Frame Relay and Asynchronous Transfer Mode (ATM). Each Cisco device that supports CDP stores the information received from other devices in a table that can be viewed using the show cdp neighbors command. This table is also accessible via Simple Network Management Protocol (SNMP). The CDP table information is refreshed each time an announcement is received, and the holdtime for that entry is reinitialized. The holdtime specifies the lifetime of an entry in the table - if no announcements are received from a device for a period in excess of the holdtime, the device information is discarded (default 180 seconds).

The information contained in CDP announcements varies by the type of device and the version of the operating system running on it. This information may include the operating system version, hostname, every address (i.e. IP address) from all protocol(s) configured on the port where CDP frame is sent, the port identifier from which the announcement was sent, device type and model, duplex setting, VTP domain, native VLAN, power draw (for Power over Ethernet devices), and other device specific information. The details contained in these announcements is easily extended due to the use of the type-length-value (TLV) frame format. See external links for a technical definition.

Hewlett-Packard removed support for transmitting CDP from HP Procurve products shipped after February 2006 and all future software upgrades. Receiving and processing CDP information is still supported. CDP support was replaced with IEEE 802.1AB Link Layer Discovery Protocol (LLDP), an IEEE standard that is implemented by multiple vendors and is functionally similar to CDP.Several other manufacturers, including Dell and Netgear have used the brand-neutral name Industry Standard Discovery Protocol (ISDP) to refer to their implementations of a CDP-compatible protocol.

CDP was the abbreviation used by Cabletron who wrote the RFC 2641 for the discovery protocol. Cabletron's VlanHello Protocol Specification Version 4

ERS 3500 and ERS 2500 series

Ethernet Routing Switch 3500 Series and Ethernet Routing Switch 2500 Series or (ERS 3500 and ERS 2500) in data computer networking terms are stackable routing switches designed and manufactured by Avaya.

The Switches can be stacked up to eight units high through a 'stacking' configuration; Avaya markets this capability under the term 'Avaya Virtual Enterprise Network Architecture (VENA) Stackable Chassis'. This series of Switches consists of six ERS 3500 models, the ERS 3526T, ERS 3526T-PWR+, ERS 3510GT, ERS 3510GT-PWR+, ERS3524GT, ERS3524GT-PWR+ and four different ERS 2500 models, the ERS 2526T, ERS 2526T-PWR, ERS 2550T and the ERS 2550T-PWR. The 'PWR' suffix designation identifies the Switch that can provide Power-over-Ethernet on the copper Ethernet ports, the '+' suffix designation indicates that the Switch can provide PoE plus on the copper ports. These Switches are all covered by Avaya's Lifetime warranty.

Ethernet Alliance

The Ethernet Alliance was incorporated in the US state of California in August 2005 and officially launched in January 2006 as a non-profit industry consortium to promote and support Ethernet. The objectives were to provide an unbiased, industry-based source of educational information; to ensure interoperability among disparate, standards-based components and systems; to support the development of standards that support Ethernet technology; and to bring together the Ethernet industry to collaborate on the future of the technology.

Ethernet Powerlink

Ethernet Powerlink is a deterministic real-time protocol for standard Ethernet. It is an open protocol managed by the Ethernet POWERLINK Standardization Group (EPSG). It was introduced by Austrian automation company B&R in 2001.

This protocol has nothing to do with power distribution via Ethernet cabling or power over Ethernet (PoE), power line communication, or Bang & Olufsen's PowerLink cable.

Foundation Fieldbus

Foundation Fieldbus (styled Foundation Fieldbus) is an all-digital, serial, two-way communications system that serves as the base-level network in a plant or factory automation environment. It is an open architecture, developed and administered by FieldComm Group.

It is targeted for applications using basic and advanced regulatory control, and for much of the discrete control associated with those functions. Foundation Fieldbus technology is mostly used in process industries, but has recently been implemented in powerplants.

Two related implementations of Foundation Fieldbus have been introduced to meet different needs within the process automation environment. These two implementations use different physical media and communication speeds.

Foundation Fieldbus H1 - Operates at 31.25 kbit/s and is generally used to connect to field devices and host systems. It provides communication and power over standard stranded twisted-pair wiring in both conventional and intrinsic safety applications. H1 is currently the most common implementation.

HSE (High-speed Ethernet) - Operates at 100/1000 Mbit/s and generally connects input/output subsystems, host systems, linking devices and gateways. It doesn't currently provide power over the cable, although work is under way to address this using the IEEE802.3af Power over Ethernet (PoE) standard.Foundation Fieldbus was originally intended as a replacement for the 4-20 mA standard, and today it coexists alongside other technologies such as Modbus, Profibus, and Industrial Ethernet. Foundation Fieldbus today enjoys a growing installed base in many heavy process applications such as refining, petrochemicals, power generation, and even food and beverage, pharmaceuticals, and nuclear applications. Foundation Fieldbus was developed over a period of many years by the International Society of Automation, or ISA, as SP50. In 1996 the first H1 (31.25 kbit/s) specifications were released. In 1999 the first HSE (High Speed Ethernet) specifications [1] were released. The International Electrotechnical Commission (IEC) standard on field bus, including Foundation Fieldbus, is IEC 61158. Type 1 is Foundation Fieldbus H1, while Type 5 is Foundation Fieldbus HSE.

A typical fieldbus segment consists of the following components.

H1 card - fieldbus interface card (It is common practice to have redundant H1 cards, but ultimately this is application specific)

PS - Bulk power (Vdc) to Fieldbus Power Supply

FPS - Fieldbus Power Supply and Signal Conditioner (Integrated power supplies and conditioners have become the standard nowadays)

T - Terminators (Exactly 2 terminators are used per fieldbus segment. One at the FPS and one at the furthest point of a segment at the device coupler)

LD - Linking Device, alternatively used with HSE networks to terminate 4-8 H1 segments acting as a gateway to an HSE backbone network.

And fieldbus devices, (e.g. transmitters, transducers, etc.)segment diagram on flickr

An explanation of how Foundation Fieldbus works and how it is used in continuous process control is in the Foundation Fieldbus Primer which may be found at the Fieldbus Inc. website.

Future Launchers Preparatory Programme

The Future Launchers Preparatory Programme (FLPP) is a technology development and maturation programme of the European Space Agency (ESA). It develops technologies for the application in future European launch vehicles (launchers) and in upgrades to existing launch vehicles. By this it helps to reduce time, risk and cost of launcher development programmes.

Started in 2004, the programmes initial objective was to develop technologies for the Next Generation Launcher (NGL) to follow Ariane 5. With the inception of the Ariane 6 project, the focus of FLPP was shifted to a general development of new technologies for European launchers.

FLPP develops and matures technologies that are deemed promising for future application but currently do not have a sufficiently high technology readiness level (TRL) to allow a clear assessment of their performance and associated risk. Those technologies typically have an initial TRL of 3 or lower. The objective is to raise the TRL up to about 6, thus creating solutions which are proven under relevant conditions and can be integrated into development programmes with reduced cost and limited risk.

IEEE 2030

IEEE 2030 was a project of the standards association of the Institute of Electrical and Electronics Engineers (IEEE) that developed a "Guide for Smart Grid Interoperability of Energy Technology and Information Technology Operation with the Electric Power System (EPS), and End-Use Applications and Loads".

IEEE 802.3

IEEE 802.3 is a working group and a collection of Institute of Electrical and Electronics Engineers (IEEE) standards produced by the working group defining the physical layer and data link layer's media access control (MAC) of wired Ethernet. This is generally a local area network (LAN) technology with some wide area network (WAN) applications. Physical connections are made between nodes and/or infrastructure devices (hubs, switches, routers) by various types of copper or fiber cable.

802.3 is a technology that supports the IEEE 802.1 network architecture.

802.3 also defines LAN access method using CSMA/CD.

Jack PC

Jack PC is a thin client device that is approximately the size of a network wall port. Its design allows for one's monitor, keyboard & mouse to plug straight into the wall-mounted unit. Jack PC operates in an SBC (Server Based Computing) environment.

The Jack PC thin client computers are connected at the back side through Ethernet cables to the building's LAN and receive Power over Ethernet (or 802.3af) through the existing enterprise infrastructure.

Jack PC is also notable in that it consumes very little power. Some tests have found it to consume as little as 5 W, not counting monitor and other external peripherals.

Juniper EX-Series

Juniper EX-Series is a series of Ethernet network switches designed and manufactured by Juniper Networks. These switches run on Juniper's network operating system, JUNOS. Juniper's then CEO and present Chairman, Scott Kriens said that the product launch marked the beginning of a transcending chapter in Juniper's history, declaring, "The switch is on". The EX series was launched 12 years after the company's founding in 1996.

Link Layer Discovery Protocol

The Link Layer Discovery Protocol (LLDP) is a vendor-neutral link layer protocol used by network devices for advertising their identity, capabilities, and neighbors on an IEEE 802 local area network, principally wired Ethernet. The protocol is formally referred to by the IEEE as Station and Media Access Control Connectivity Discovery specified in IEEE 802.1AB and IEEE 802.3 section 6 clause 79.LLDP performs functions similar to several proprietary protocols, such as Cisco Discovery Protocol, Foundry Discovery Protocol, Nortel Discovery Protocol and Link Layer Topology Discovery.

Mobile VoIP

Mobile VoIP or simply mVoIP is an extension of mobility to a Voice over IP network. Two types of communication are generally supported: cordless/DECT/PCS protocols for short range or campus communications where all base stations are linked into the same LAN, and wider area communications using 3G/4G protocols.

There are several methodologies that allow a mobile handset to be integrated into a VoIP network. One implementation turns the mobile device into a standard SIP client, which then uses a data network to send and receive SIP messaging, and to send and receive RTP for the voice path. This methodology of turning a mobile handset into a standard SIP client requires that the mobile handset support, at minimum, high speed IP communications. In this application, standard VoIP protocols (typically SIP) are used over any broadband IP-capable wireless network connection such as EVDO rev A (which is symmetrical high speed — both high speed up and down), HSPA, Wi-Fi or WiMAX.

Another implementation of mobile integration uses a soft-switch like gateway to bridge SIP and RTP into the mobile network's SS7 infrastructure. In this implementation, the mobile handset continues to operate as it always has (as a GSM or CDMA based device), but now it can be controlled by a SIP application server which can now provide advanced SIP-based services to it. Several vendors offer this kind of capability today.

Mobile VoIP will require a compromise between economy and mobility. For example, voice over Wi-Fi offers potentially free service but is only available within the coverage area of a single Wi-Fi access point. Cordless protocols offer excellent voice support and even support base station handoff, but require all base stations to communicate on one LAN as the handoff protocol is generally not supported by carriers or most devices.

High speed services from mobile operators using EVDO rev A or HSPA may have better audio quality and capabilities for metropolitan-wide coverage including fast handoffs among mobile base stations, yet may cost more than Wi-Fi-based VoIP services.

As device manufacturers exploited more powerful processors and less costly memory, smartphones became capable of sending and receiving email, browsing the web (albeit at low rates) and allowing a user to watch TV. Mobile VoIP users were predicted to exceed 100 million by 2012 and InStat projects 288 million subscribers by 2013.The mobile operator industry business model conflicts with the expectations of Internet users that access is free and fast without extra charges for visiting specific sites, however far away they may be hosted. Because of this, most innovations in mobile VoIP will likely come from campus and corporate networks, open source projects like Asterisk, and applications where the benefits are high enough to justify expensive experiments (medical, military, etc.).

SpiderCloud Wireless

SpiderCloud Wireless was founded in November 2006 as Evoke Networks by Peter Wexler, Allan Baw, and Mark Gallagher in downtown Palo Alto. The trio incubated the company as Copivia Inc. and hired Mike Gallagher as CEO in October 2007. The company closed Series-A funding in January 2008 and soon after changed the company name to SpiderCloud Wireless. The company is now headquartered in Milpitas, California. The company is backed by investors Charles River Ventures, Matrix Partners, Opus Capital and Shasta Ventures. It has raised around $125 million in venture capital and is generating revenue from customers such as Vodafone UK, Vodafone Netherlands, Verizon Wireless, Warid Telecom and more. The company helps mobile operators improve service quality for enterprise customers. The company competes against established telecom equipment providers such as Alcatel-Lucent, Ericsson and Nokia Solutions and Networks.SpiderCloud Wireless develops scalable and multi-access Small Cell network platforms that allow mobile operators to deliver cellular and Wi-Fi coverage, capacity and smart applications to enterprises and venues of any size. The E-RAN system is made up of one rack unit sized Services Node that manages multiple single-carrier or dual-carrier Radio Nodes operating in 3G, LTE and unlicensed spectrum.SpiderCloud Radio Node (SCRN): Radio Nodes (RNs) are high-capacity, power-over-Ethernet (PoE) capable, small cells. In any deployment, multiple RNs are deployed inside an enterprise or venue, and are connected to the Services Node using standard Ethernet LAN infrastructure. SpiderCloud offers a portfolio of Radio Nodes that support UMTS, LTE, LTE-U and LAA.

SpiderCloud Services Node (SCSN): Enterprise on-premises controller of over 100 self-organizing Radio Nodes that can be installed in just days using an enterprise-Ethernet Local Area Network (LAN) as a managed service by a mobile operator’s network.

SpiderCloud was acquired by Corning Inc. on July 19, 2017.

VoIP phone

A VoIP phone or IP phone uses voice over IP technologies for placing and transmitting telephone calls over an IP network, such as the Internet, instead of the traditional public switched telephone network (PSTN).Digital IP-based telephone service uses control protocols such as the Session Initiation Protocol (SIP), Skinny Client Control Protocol (SCCP) or various other proprietary protocols.

Wireless Router Application Platform

The Wireless Router Application Platform (WRAP) is a format of single board computer defined by Swiss company PC Engines. This is specially designed for wireless router, firewall, load balancer, VPN or other network appliances.

Ethernet family of local area network technologies

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