Ethernet

Power over Ethernet benefits, applications and certifications

Power over Ethernet (PoE) technology has been around nearly 20 years, but there’s still confusion about what it can and can’t do for end users and what the certifications mean.

By Craig Chabot August 27, 2021
Courtesy: University of New Hampshire InterOperability Laboratory (UNH-IOL).

 

Learning Objectives

  • Power over Ethernet (PoE) is becoming more common in industrial manufacturing.
  • Standards and certifications and what they mean is a common challenge for users.
  • The Ethernet Alliance PoE Certification Program is working to streamline and clarify issues for users.

Power over Ethernet (PoE) is a technology for Ethernet end devices that provides the ability to transmit and receive data as well as receive power over the same cabling. It defines power sourcing equipment (PSE) which usually takes the form of an Ethernet switch, and powered devices (PD) which are the end devices that need power. PDs vary greatly depending on their intended application, including cameras, wireless access points, lighting and others.

PoE technology has been a part of the enterprise grade computer networking landscape for nearly 20 years. Since its introduction, PoE has expanded into consumer and industrial settings as PoE application diversity has greatly increased. As the technology evolved over this timeframe, significant challenges for manufacturers and end users of PoE products arose, in many cases due to improper claims of conformity or compliance with standardized PoE.

Additionally, simple confusion became commonplace, stemming from myriad practices in marketing the flavors of PoE supported by certain products (or claimed to be supported). What remains clear is the unparalleled value of PoE for end device applications – old, new and upcoming.

History of standardization

Ethernet technologies are standardized by the IEEE and are developed and defined in the IEEE’s 802.3 Working Group. For the first few decades of its work, IEEE 802.3 focused on data communications over various forms of media. With a focus on interoperability, Ethernet eventually became synonymous to the lay person with the port and associated cables eventually found on almost all computer and network equipment. This consists of the RJ-45 jack, connector and category cabling, which contains four twisted pairs of copper cabling.

Once 1000Base-T Ethernet (Gigabit full duplex) became a mainstay in computer networks, more end device applications were being developed.

Eventually, a desire grew to power Ethernet end devices through the very same cabling that provided network access. This desire was followed by the first IEEE 802.3 PoE project under the name IEEE 802.3af, which defined the initial three power classes for PDs and PSEs for power applications up to 15.4 W. IEEE 802.3af was completed in 2003 and is the 33rd clause within IEEE 802.3.

A few years later, there was already a need to increase available power for new applications, which led to the next PoE project, IEEE 802.3at. It remained in clause 33 and defined Type 2 PDs and PSEs that supported a new fourth power class, which defined operation up to 25.5 W.

Next to come was IEEE 802.3bt, which finished in 2018 after several years of development. This standard defined two additional types and four additional power classes. Type 3 PDs and PSEs encompass classes 5 and 6 providing up to 51 W, with Type 4 PDs and PSEs encompassing classes 7 and 8 with available power increased to 71 W.

Image 1: RJ-45 jacks and ethernet cables. Courtesy: University of New Hampshire InterOperability Laboratory (UNH-IOL).

Image 1: RJ-45 jacks and ethernet cables. Courtesy: University of New Hampshire InterOperability Laboratory (UNH-IOL).

PoE market confusion and the need for certification

With a brief overview of the history of PoE understood, how you would refer to a particular PD or PSE? Imagine the challenge from the point of view of the device manufacturer and the end user. You have a Class 4 PD.

How do you convey or understand what it supports? The class alone, or “IEEE 802.3at,” “Type 2,” “25.5 W,” “IEEE 802.3 Clause 33 PoE?” For those with technical backgrounds already aware of what PoE is, referring to the project name is sufficient. To a l will likely mean almost nothing to the layperson.

What happened after IEEE 802.3at was completed is not surprising. Marketing teams throughout the industry came up with their own terms to describe what their products supported. To confound this further, there were devices being sold making claims to be compliant or conformant that may not have even been designed to the IEEE 802.3 standard (Proprietary forms of PoE that do not promote interoperability like IEEE 802.3 PoE also exist). So, in addition to devices designed against the same IEEE 802.3 technology being marketed using different terminologies, there were devices claiming support of standard PoE with no evidence.

PoE had already proven itself as an invaluable technology for lower-powered applications like IP cameras, low power wireless access points, etc.

The concern was the technology’s brand and name recognition would be tarnished, discouraging forward momentum in developing new end device applications, like display screens, higher power access points, industrial lighting and controls, audio speakers, building automation, etc. An effort to alleviate these problems was born within the Ethernet Alliance, a global, non-profit, industry consortium of member organizations dedicated to the continued success and advancement of Ethernet technologies.

Image 2: A PSE logo class number equal to or greater than the logo class number shown on the PD assures that the PD will get the requisite amount of power for its intended application. Courtesy: University of New Hampshire InterOperability Laboratory (UNH-IOL).

Image 2: A PSE logo class number equal to or greater than the logo class number shown on the PD assures that the PD will get the requisite amount of power for its intended application. Courtesy: University of New Hampshire InterOperability Laboratory (UNH-IOL).

Ethernet Alliance Certification

Though the IEEE 802.3bt project was a couple of years from completion, a group of Ethernet Alliance members knew the existing market confusion should be addressed while laying the foundation for the next generation of PoE products in the coming years.

The group eventually settled on a certification program with the goal of solving market confusion on both sides. The Ethernet Alliance PoE Certification Program provides use of a branded logo that, while simple in design, conveys valuable information to the end user including whether the device is a PSE or PD, and what power class it supports. It also establishes the product is built in accordance with IEEE 802.3 standards.

In an attempt to leverage what has always been Ethernet’s biggest strength – interoperability, this logo would make it as easy as possible to assure interoperability of PoE products.

A PSE logo class number equal to or greater than the logo class number shown on the PD assures that the PD will get the requisite amount of power for its intended application.

In late 2017, the first generation of the Ethernet Alliance PoE Certification Program was launched to provide certification for Type 1 and Type 2 PDs and PSEs. Last year, following IEEE 802.3bt’s completion, the Ethernet Alliance Gen2 PoE Certification was launched.

In the midst of the COVID-19 pandemic, testing and certification efforts moved ahead, with the first batch of PDs and PSEs being certified during a pilot testing program, and are viewable on the program’s Certified Product Registry, with all other certified products.

Table 1: Power levels defined by 802.3bt. All PoE devices are interoperable; the power supplied at the PSE is defined greater due to channel losses. Courtesy: University of New Hampshire InterOperability Laboratory (UNH-IOL).

Table 1: Power levels defined by 802.3bt. All PoE devices are interoperable; the power supplied at the PSE is defined greater due to channel losses. Courtesy: University of New Hampshire InterOperability Laboratory (UNH-IOL).

As the application space for PoE continues to grow, interoperability, the ease of use and installation are more important than ever. End users need the ability to quickly verify that a PSE or PD will “just work” in their network. Additionally, PoE manufacturers need a method to clearly communicate their product’s features while identifying that they are based on IEEE 802.3 Ethernet standards. The Ethernet Alliance PoE Certification Program has provided solutions for these challenges and will improve PoE for all as more products get certified.

Craig Chabot is the manager of the Wireless and Power over Ethernet (PoE) Testing Services Groups at the University of New Hampshire InterOperability Laboratory (UNH-IOL). Edited by Chris Vavra, web content manager, Control Engineering, CFE Media and Technology, cvavra@cfemedia.com.

MORE ANSWERS

Keywords: Power over Ethernet, Ethernet standards

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Craig Chabot
Author Bio: Craig Chabot is the Manager of the Wireless and Power over Ethernet (PoE) Testing Services Groups at the University of New Hampshire InterOperability Laboratory (UNH-IOL). As and undergrad at UNH, Chabot began work at the UNH-IOL in 2008 in the Wireless Group where he gained knowledge in computer networking, testing methodologies and the IEEE 802.11 standard. After obtaining his Bachelors of Science in Mathematics in 2011, Chabot continued work in the Wireless Group furthering his understanding of 802.11 in addition to developing new testing services for the group. In the fall of 2013, Chabot took on his new role leading the Wireless Testing Services. In 2015, Chabot joined the Broadband Industry at the UNH-IOL to assist with operations and began managing the PoE group. Chabot regularly attends IEEE 802.3 meetings and has contributed as PICS editor to 802.3bu and 802.3bt working groups.