In networking, IEEE 802.3af and IEEE 802.3at are two standards that
are used for Power over Ethernet (PoE). PoE is a technology that allows for
the transmission of electrical power along with data over a standard
Ethernet cable. This technology eliminates the need for separate power
cables, simplifies network installations, and improves device mobility. In
this article, we will discuss these two standards in detail.
IEEE 802.3af: Also known as PoE or PoE Type 1, this standard was first
introduced in 2003. It provides up to 15.4 watts of power to network devices
and can transmit power over distances of up to 100 meters. This standard
requires Category 5 (or higher) cabling to deliver power to the device. IEEE
802.3af uses two of the four pairs of wires in an Ethernet cable to transmit
power, allowing for power and data to be sent over a single cable.
IEEE 802.3at: Also known as PoE+ or PoE Type 2, this standard was
introduced in 2009. It provides up to 30 watts of power to network devices
and can transmit power over distances of up to 100 meters. This standard
requires Category 5e (or higher) cabling to deliver power to the device.
IEEE 802.3at uses all four pairs of wires in an Ethernet cable to transmit
power, allowing for more efficient power delivery.
One key difference between the two standards is the amount of power that
they can deliver to network devices. IEEE 802.3af can provide up to 15.4
watts, while IEEE 802.3at can provide up to 30 watts. This increased power
capacity makes IEEE 802.3at ideal for devices that require more power, such
as PTZ cameras, video phones, and wireless access points with multiple
radios.
Also, Check: Top 50+ Cisco VoIP IPT and above Level Interview Questions and Answers
Another difference between the two standards is the method of negotiation
between the power sourcing equipment (PSE) and the powered device (PD). IEEE
802.3af uses a simple voltage test to determine if the PD is PoE-enabled,
while IEEE 802.3at uses a more complex negotiation process to determine the
power requirements of the PD.
Both standards are widely used in network deployments, and most network
devices that support PoE will work with both standards. However, it is
important to note that not all devices are compatible with PoE technology.
Devices must have built-in PoE support or use an external PoE splitter to
convert PoE power to the appropriate voltage for the device.
In conclusion, IEEE 802.3af and IEEE 802.3at are two PoE standards that are
widely used in networking. While both standards allow for the transmission
of power and data over a single Ethernet cable, they differ in the amount of
power that they can deliver to network devices and the negotiation process
used to determine power requirements. As the demand for higher-powered
devices continues to grow, newer PoE standards, such as IEEE 802.3bt, are
being introduced to meet these evolving needs.