Power Sourcing Equipment (PSE) in IEEE 802.3 Standard

Overview

Power Sourcing Equipment (PSE) is essential in networks for delivering power along with data over Ethernet cables. It usually refers to devices like switches and hubs that supply power to Powered Devices (PDs) such as IP cameras, VoIP phones, and wireless access points.

PSE vs. PoDL PSE

PSE in the IEEE 802.3 standard generally refers to equipment that provides power alongside data over Ethernet cables, typically associated with Power over Ethernet (PoE).

PoDL PSE, or Power over Data Lines PSE, specifically denotes PSEs operating with single balanced twisted-pair PHYs, as per Clause 104 of IEEE 802.3. PoDL is significant in contexts like automotive and industrial controls where power and data delivery over a single pair is advantageous.

IEEE 802.3-2018 Addendums and Related Clauses

Key addenda to the IEEE 802.3-2018 standard relevant to power delivery over Ethernet are as follows:

• 802.3af (Approved in 2003-06-12): Known as PoE in the market, detailed in Clause 33, delivering up to 15.4W of power.

• 802.3at (Approved in 2009-09-11): Marketed as PoE+, enhancing PoE as covered in Clause 33, increasing power delivery to up to 30W.

• 802.3bt (Approved in 2018-09-27): Known as 4PPoE in the market, outlined in Clause 33. Type 3 delivers up to 60W, and Type 4 up to 100W.

• 802.3bu (Approved in 2016-12-07): Formerly referred to as PoDL, detailed in Clause 104. Introduces Classes 0 - 9. Class 9 PoDL PSE delivers up to ~65W

Kernel Naming Convention Recommendations

For clarity and consistency within the Linux kernel’s networking subsystem, the following naming conventions are recommended:

• For general PSE (PoE) code, use “c33_pse” key words. For example: enum ethtool_c33_pse_admin_state c33_admin_control;. This aligns with Clause 33, encompassing various PoE forms.

• For PoDL PSE - specific code, use “podl_pse”. For example: enum ethtool_podl_pse_admin_state podl_admin_control; to differentiate PoDL PSE settings according to Clause 104.

Summary of Clause 33: Data Terminal Equipment (DTE) Power via Media Dependent Interface (MDI)

Clause 33 of the IEEE 802.3 standard defines the functional and electrical characteristics of Powered Device (PD) and Power Sourcing Equipment (PSE). These entities enable power delivery using the same generic cabling as for data transmission, integrating power with data communication for devices such as 10BASE-T, 100BASE-TX, or 1000BASE-T.

Summary of Clause 104: Power over Data Lines (PoDL) of Single Balanced Twisted-Pair Ethernet

Clause 104 of the IEEE 802.3 standard delineates the functional and electrical characteristics of PoDL Powered Devices (PDs) and PoDL Power Sourcing Equipment (PSEs). These are designed for use with single balanced twisted-pair Ethernet Physical Layers. In this clause, ‘PSE’ refers specifically to PoDL PSE, and ‘PD’ to PoDL PD. The key intent is to provide devices with a unified interface for both data and the power required to process this data over a single balanced twisted-pair Ethernet connection.