“Fast-PoE and Perpetual-PoE - are these new standards or not?”
Technology “Power-over-Ethernet”, or abbreviated “PoE”, has firmly entered our lives and is inextricably linked with the vast majority of installations of IP-telephony, video surveillance and wireless networks. The last update of the IEEE 802.3 standard, in terms of the familiar PoE, was carried out in 2012. Then, during the next revision of the standard, already adopted additions were included in it, including 802.3at-2009 (Power over Ethernet enhancements - 25.5 W), known to us as “PoE +”. Today, products supporting Fast-PoE and Perpetual-PoE technologies are entering the network switch market. Whether these capabilities of the switches are part of the standard or not, let's try to understand our article.
Right now, the IEEE 802.3 standard includes the following approved additions regarding PoE:
802.3af || 2003-06 || Power over Ethernet (15.4 W)
802.3at || 2009-09 || Power over Ethernet enhancements (25.5 W)
802.3au || 2006-06 || Isolation requirements for Power over Ethernet (802.3-2005 / Cor 1)
802.3bt || 2018-09 || Third generation Power over Ethernet with up to 100 W using all 4 pairs balanced twisted-pair cabling (4PPoE), including 10GBASE-T, lower standby power and specific enhancements to support IoT applications (eg lighting, sensors, building automation).
The 802.3af / at / au standards have been successfully implemented and are widely used; 802.3bt (PoE ++) was ratified only last year and is starting to gain its niche in the market. Characteristics of standards:
Also in the current 2019, the IEEE 802.3cq working group plans to make editorial and technical corrections, clarifications and clarifications to section 33 of the standard (IEEE Std 802.3-2018 Clause 33), without adding new features. This is necessary to improve the accuracy and clarity of the standard.
802.3cq || (TBD) || Power over Ethernet over 2 pairs (maintenance) - scheduled for summer 2019
Actually, none of the above additions to the standard describes such concepts as “Fast-PoE” and “Perpetual-PoE”. The fact is that the standard describes the requirements and the reciprocal operation of PSE, PD and cable line (“Power Source Equipment”, “Powered Device”). Approximately as in the diagram below:
PSE, in the most general case, is any switch with PoE. The switch architecture we are familiar with consists of “Control Plane” and “Data Plane”, and in the case of PoE, an independent PoE controller is also added to this circuit. It is the PoE controller that is responsible for the classification of PD and for supplying voltage to the line. The logical boundary in this circuit passes just through the PoE controller. So, on the one hand of this border, we have the PoE standard, which describes the operation towards the cable line, and on the other hand, we have not described the operation of this same controller with the rest of the switch elements and its operating system. That is, before that it was believed that the PoE controller is powered and works 100% of the time, the switches never reboot and do not lose power. The Fast-PoE and Perpetual-PoE technologies are an improvement in the operation of the switch,
“Perpetual PoE” : saves the power supply to the line during a soft reboot (“warm reboot”)
“Fast PoE” : provides power to the line after a power reboot (“cold reboot”) until the OC of
the Perpetual PoE switch is fully loaded
Provides the ability Reboot the switches while providing continuous power to devices connected to the PoE. Currently, rebooting the switch causes a temporary loss of power on the ports, which leads to a complete reboot of all connected devices. This is very undesirable in the work environment. Perpetual PoE alleviates this unpleasant problem by continuing to provide constant power through the PoE ports to external devices, even when the power switch is rebooting.
In network switches, the PoE subsystem is powered by the same power source as the switch itself. The power of each switch subsystem, including the PoE subsystem, is controlled by FPGA. Today, when the switch is rebooted with a command from the OS, the FPGA first turns off the power, and then turns on all the switch subsystems, including the PoE subsystem. When the PoE subsystem shuts down, power is cut off on all ports, thereby disconnecting all connected devices. That is, while the switch itself is connected to the PSU and receiving power from it, the Perpetual PoE technology ensures that the FPGA will keep the PoE subsystem on and provide continuous power on all PoE ports for all connected devices, even when the OS switch is rebooted.
"Fast PoE"
The standard implementation of the switches provided that after a cold reboot, PoE is only delivered to the line after the switch loads its own OS and it issues instructions to the PoE controller. This usually happens a few minutes after power is supplied to the switch. Fast PoE is designed to power PoE devices as soon as the switch turns on. For this, the PoE settings are stored in the EEPROM of the PoE controller. When the switch is turned on, the PoE controller loads the last saved configuration from the EEPROM and starts to automatically power up without waiting for the switch OS to boot. Within a few seconds, the PD will resume power, and the PD and PSE will boot in parallel, rather than sequentially. This minimizes the time of possible interruption of communication.
Although these enhancements may seem rather prosaic from the point of view of the client, they consist of several very important changes in the architecture of the switch. Both in the hardware part - the PoE controller itself, and the software part - in the part of the FPGA code, which prevents activation of the PoE subsystem reset, and the part of the OS switches, which controls the FPGA under the guise of “Perpetual PoE” control. It is also important to note that “Perpetual PoE” and “Fast PoE” are completely independent both from each other and from the PoE standard itself.
These improvements can be extremely popular and useful for critical infrastructure projects, where disruption is always painful, both from a business point of view and from a security point of view.
As part of the Extreme Networks product line, ExtremeSwitching X465 Series switches support Fast-PoE and Perpetual-PoE, as well as PoE ++ (802.3bt).
If you have questions, please contact our local Extreme Networks representative .
Right now, the IEEE 802.3 standard includes the following approved additions regarding PoE:
802.3af || 2003-06 || Power over Ethernet (15.4 W)
802.3at || 2009-09 || Power over Ethernet enhancements (25.5 W)
802.3au || 2006-06 || Isolation requirements for Power over Ethernet (802.3-2005 / Cor 1)
802.3bt || 2018-09 || Third generation Power over Ethernet with up to 100 W using all 4 pairs balanced twisted-pair cabling (4PPoE), including 10GBASE-T, lower standby power and specific enhancements to support IoT applications (eg lighting, sensors, building automation).
The 802.3af / at / au standards have been successfully implemented and are widely used; 802.3bt (PoE ++) was ratified only last year and is starting to gain its niche in the market. Characteristics of standards:
Also in the current 2019, the IEEE 802.3cq working group plans to make editorial and technical corrections, clarifications and clarifications to section 33 of the standard (IEEE Std 802.3-2018 Clause 33), without adding new features. This is necessary to improve the accuracy and clarity of the standard.
802.3cq || (TBD) || Power over Ethernet over 2 pairs (maintenance) - scheduled for summer 2019
Actually, none of the above additions to the standard describes such concepts as “Fast-PoE” and “Perpetual-PoE”. The fact is that the standard describes the requirements and the reciprocal operation of PSE, PD and cable line (“Power Source Equipment”, “Powered Device”). Approximately as in the diagram below:
PSE, in the most general case, is any switch with PoE. The switch architecture we are familiar with consists of “Control Plane” and “Data Plane”, and in the case of PoE, an independent PoE controller is also added to this circuit. It is the PoE controller that is responsible for the classification of PD and for supplying voltage to the line. The logical boundary in this circuit passes just through the PoE controller. So, on the one hand of this border, we have the PoE standard, which describes the operation towards the cable line, and on the other hand, we have not described the operation of this same controller with the rest of the switch elements and its operating system. That is, before that it was believed that the PoE controller is powered and works 100% of the time, the switches never reboot and do not lose power. The Fast-PoE and Perpetual-PoE technologies are an improvement in the operation of the switch,
“Perpetual PoE” : saves the power supply to the line during a soft reboot (“warm reboot”)
“Fast PoE” : provides power to the line after a power reboot (“cold reboot”) until the OC of
the Perpetual PoE switch is fully loaded
Provides the ability Reboot the switches while providing continuous power to devices connected to the PoE. Currently, rebooting the switch causes a temporary loss of power on the ports, which leads to a complete reboot of all connected devices. This is very undesirable in the work environment. Perpetual PoE alleviates this unpleasant problem by continuing to provide constant power through the PoE ports to external devices, even when the power switch is rebooting.
In network switches, the PoE subsystem is powered by the same power source as the switch itself. The power of each switch subsystem, including the PoE subsystem, is controlled by FPGA. Today, when the switch is rebooted with a command from the OS, the FPGA first turns off the power, and then turns on all the switch subsystems, including the PoE subsystem. When the PoE subsystem shuts down, power is cut off on all ports, thereby disconnecting all connected devices. That is, while the switch itself is connected to the PSU and receiving power from it, the Perpetual PoE technology ensures that the FPGA will keep the PoE subsystem on and provide continuous power on all PoE ports for all connected devices, even when the OS switch is rebooted.
"Fast PoE"
The standard implementation of the switches provided that after a cold reboot, PoE is only delivered to the line after the switch loads its own OS and it issues instructions to the PoE controller. This usually happens a few minutes after power is supplied to the switch. Fast PoE is designed to power PoE devices as soon as the switch turns on. For this, the PoE settings are stored in the EEPROM of the PoE controller. When the switch is turned on, the PoE controller loads the last saved configuration from the EEPROM and starts to automatically power up without waiting for the switch OS to boot. Within a few seconds, the PD will resume power, and the PD and PSE will boot in parallel, rather than sequentially. This minimizes the time of possible interruption of communication.
Although these enhancements may seem rather prosaic from the point of view of the client, they consist of several very important changes in the architecture of the switch. Both in the hardware part - the PoE controller itself, and the software part - in the part of the FPGA code, which prevents activation of the PoE subsystem reset, and the part of the OS switches, which controls the FPGA under the guise of “Perpetual PoE” control. It is also important to note that “Perpetual PoE” and “Fast PoE” are completely independent both from each other and from the PoE standard itself.
These improvements can be extremely popular and useful for critical infrastructure projects, where disruption is always painful, both from a business point of view and from a security point of view.
As part of the Extreme Networks product line, ExtremeSwitching X465 Series switches support Fast-PoE and Perpetual-PoE, as well as PoE ++ (802.3bt).
If you have questions, please contact our local Extreme Networks representative .
