Power over Ethernet (PoE) is a network feature defined by the IEEE 802.3af and 802.3at standards. PoE switch is used to power networked devices with Ethernet cables via the existing data connection.
PoE-compatible devices can be used as Power SOURCES (PSE = Power Sourcing Equipment), Powered Devices (PD = Powered Device), or sometimes both.
The device supplying power is a PSE, while the device that is powered is PD equipment.
Most PES are network switches or PoE injectors for use with PoE-free switches. Some common examples of PD (Powered Device): VoIP phones, WiFi access points, and IP cameras.
What are the advantages of PoE?
Since PoE allows you to use a single cable for power and data transmission, it allows you to save the cost of purchasing and deploying cables for network equipment and VoIP phones.
PoE greatly facilitates the installation or expansion of a network and also reduces the cost in buildings where the installation of new power supplies would be too expensive or impractical.
The use of PoE allows you to fix devices in places where the installation of power supply would be inconvenient, such as in false ceilings.
Using PoE can reduce the number of cables and electrical outlets needed in a cluttered piece of equipment or in a wiring closet.
What is PoE +?
The latest PoE update is the IEEE 802.3at standard, also known as PoE +. The main difference between the 802.3af (PoE) and 802.3at (PoE +) standards is as follows: PoE + PES can provide dual power over a single Ethernet cable.
PoE + PSEs can power both PoE and PoE + Powered Device (PoE) devices, but PoE PES can only power PoE Powered Device (PD) devices. PoE + Powered Devices (PoE) devices require more power than PoE PES can provide.
What power supply can PoE devices provide?
PoE + devices can provide up to 30 watts per port, while PoE devices can provide up to 15.4 watts per port. However, the length of the cable always leads to a loss of power, all the more so as the wiring is long.
The minimum guaranteed power for PD equipment is 12.95 watts per port for PoE and 25.5 watts per port for PoE +.
PES also has a maximum power budget, which is the total amount of power they can provide to the PDs (Powered Device) at a given time, measured in watts.
Most PES do not have enough power budget to power all PoE-compatible ports with the maximum power possible because most users do not require as much power.
When looking to buy a PoE-compatible PES, be sure to calculate your power budget for all the PD equipment you plan to connect.
What do PoE classes mean?
A class from 0 to 4 is assigned to devices powered by PoE and PoE + depending on how much power they need.
When a PD device (Powered Device) is connected to a PSE, it supplies its class to the PSE, so that the latter can provide it with the correct amount of power.
Class 1, 2 and 3 devices require very low, low and medium power, respectively. Class 4 devices (PoE +) require high power and are compatible with PSE PoE + only. For more information on PoE ratings,
Class 0 devices have not received a classification proper from the manufacturer. Most PES must, therefore, allocate the same amount of power for Class 0 devices as for Class 3 devices, even if the Class 0 device actually uses very little power.
However, the newer models of NETGEAR PoE + switches allow you to set the higher power limit of a PD (Powered Device) regardless of its class.
These models also allocate power to other PD devices (Powered Device) according to the power limits you have defined, and not according to the theoretical power allocation determined by the class of devices, which reduces the waste of power. power budget.