802.3at vs. 802.3af Poe: What is It, and How Are The Two Different?

What is the difference between 802.3at vs. 802.3af PoE? The main difference between them is the amount of power delivered. The 802.3af PoE standard delivers 15.4 watts to endpoint devices, while the more recent 802.3at PoE standard delivers 25.5 watts PoE endpoint devices.

So, what is Power over Ethernet (PoE)

Power over Ethernet (PoE) can be a confusing topic. It is one of the avenues of IT that cross with the need to understand basic electricity concepts. Simply put, POE is a technology that allows both data and electrical power to be transmitted over a single Ethernet cable.

PoE is defined by the IEEE 802.3af and IEEE 802.3at standards, commonly known as PoE and PoE+ respectively. The primary difference between these two standards is the amount of power delivered. PoE provides up to 15.4 watts of power per port, while PoE+ can deliver up to 30 watts. There are also higher-power PoE standards, such as 802.3bt (PoE++) that can provide up to 60 watts or more per port.

802.3at vs. 802.3af PoE: what are they?

The 802.3af Power over Ethernet standard was introduced in 2003 and would eventually support the initial explosion of IoT devices. 802.3af allowed installers to deliver power and data using one networking solution. It caused a significant increase in the deployment of powered devices (PDs) as there was no need to hire an electrician and a cabling specialist to deploy. Installers used power over Ethernet networking solutions to provide power and data on a single cable to all manner of PDs.

As time went on, device manufacturers created better solutions that required more power to operate. The 802.3at is able to provide up to 25.5 watts of power to the PD. The increase in power was now able to support more intricate devices, such as cameras with movement motors and wireless access points with increased range.

After the 802.3at Power over Ethernet Standard device manufacturers were pushing the limits of technology. Quickly, there was a complex with additional features and mechanical capabilities. However, the industry and standards development was moving slower than the demand for better standards.

Why PoE At All

PoE is a very useful standard that helps prevent the need for power adapters and network cables for devices that require both but have minimal power requirements.

Phones were a great use case for this due to falling into those needs. Most phones consumed power minimally and needed network ports for computers. This synergy helps reduce and ease the management of the end user’s workstation.

Power capacity planning is not specific to either standard but it is important to ensure you have adequate power to your switches with modular power supplies have higher end supplies with higher end supplies with high wattage.  

802.3at vs 802.3af PoE: Which should I Use?

The decision point is fairly simple. If you already have PoE-capable switches, many times determine the standards supported. In some cases, you can replace/upgrade line cards to support newer PoE standards. It is important to determine the standards. It is important to determine the standards and power requirements of the devices you need to use.

Because phones are the most common example, we will use that. If your phones only require 10W, 802.3af should suffice. If on the other hand, your phones require 19W, you will need 802.3at. At this point, if your switch is only capable of supporting 802.3af you would need to investigate upgrading/replacing, changing, or finding a different phone.

Beyond 802.3at  

Beyond these, standards are being drafted for 802.3bt and type. As the convenience of this takes off and more cases are found, we will find that increased power will be mindful when upgrading your switching gear so that you can try to support the latest devices.

Conclusions

if you have the option, on the switch side, choose 802.3at as it supports PoE and PoE+ devices. On the devices side, try to find the most efficient device possible to minimize the power requirements while also meeting any business requirements you have.

PoE can be great but if you hit the tipping point of power consumption, line cards, and switches can start to power down to conserve power so it is important to be power conscious in your decisions.