Tue. May 30th, 2023

Introduction: Ethernet Switch Power Consumption

In modern network architectures, information technology and data center managers are looking for green options for reducing the power consumption of Ethernet switches, routers and server equipment. This requires more environmentally friendly products on the market, thereby reducing operating costs. For example, Internet traffic for the entire year of 1993 totaled several hundred terabytes. In 2010, 17 years later, Internet traffic per second reached hundreds of terabytes. In fact, today, more than 50 percent of data center operating expenses are spent on equipment cooling, ie powering fans and air conditioning systems.

Traditional network equipment design requires high performance, but there is no clear measurement standard for power consumption and energy efficiency.Specifically, energy efficiency and

Network devices that support the Power over Ethernet protocol (PoE protocol) are disconnected. As a result, in the field of network market, the power consumption of equipment is increasing rapidly, especially that of high-frequency application processors.

Considering that more than 300 million Ethernet switch ports are sold each year, power loss due to idle lines presents a significant and pervasive concern. The IEEE Energy Efficient Ethernet specification emerged with the goal of dramatically reducing power consumption for the more than 600 million Ethernet ports sold each year. However, this specification fails to address the fact that when a PoE system is deployed, most of the power loss occurs in the PoE subsystem—not in the data section.

In 2010, nearly 70 million PoE system switch ports were sold in the market. This is the focus of attention for enterprises deploying IP telephony, WLAN networks, IP security applications and other applications powered by Ethernet systems. For example, a standard 48-port Ethernet switch only has to distribute 50 watts to 80 watts of power over conventional Ethernet switch and transceiver ICs. However, the switch needs to supply 370 watts to 740 watts of power on the Ethernet power supply system. This 8:1 comparison factor means that a small improvement in the energy efficiency of the PoE system can greatly improve the overall energy efficiency of the Ethernet switch.

Traditional Energy Efficient Ethernet (EEE)

In response to the ever-increasing power consumption of Ethernet switches, IEEE researched and approved the 802.3az standard. This standard is called the Energy Efficient Ethernet standard (EEE). The standard provides Low Power Idle (LPI) mode applications for Ethernet Base-T transceivers (100Mb, 1GbE and 10GbE) and backplane physical layers.

The Energy Efficient Ethernet standard is based on the basic idea of ​​disconnecting power from equipment during periods of low utilization or idle periods, and restoring power during periods of data transmission. This philosophy is based on the well-known fact that client and server Ethernet connections in a standard network environment are idle most of the time. Its data traffic peaks only happen occasionally.

The EEE specifies the Low Power Idle (LPI) protocol in detail. This protocol controls both ends of the physical connection by sending signals to realize quick adjustments to the power-saving mode of the connected device—including turning off the power supply and stopping the system’s data transmission and reception functions during the period of no data transmission. In addition, the Energy Efficient Ethernet standard specifies another protocol in detail. This protocol keeps the operating parameters of the Ethernet physical layer system in low-power idle (LPI) mode updated at all times, thereby keeping the connection stable and preventing disconnection. In addition, the Energy Efficient Ethernet standard specifies the signaling protocol on one side in detail. This protocol shows when a physical connection is needed and enables fast connection recovery. As a result, low-power idle (LPI) applications can save one watt of power per Ethernet connection at a high level of Ethernet physical layer technology. However, the Energy Efficient Ethernet standard cannot deal with the power loss of Power over Ethernet, nor can it solve the problem of how to reduce energy consumption.

Power-over-Ethernet (PoE) Energy Saving Mechanism

An important reason to use Power over Ethernet instead of traditional alternating current (AC) supply modules for powering equipment is that it can remotely shut down equipment and also reduce the amount of cabling. By controlling the turning on and off of equipment, a large amount of power is saved. For example, through a central control point, cameras used at night can be turned off during the day (and vice versa); IEEE802.11 WLAN access points can be turned on to improve coverage and bandwidth, or turned off during periods of low utilization; and IP Phones can be turned off overnight, on weekends, or during periods of inactivity.

In multiport devices, the data also demonstrate the benefits of Power over Ethernet. A single AC power supply module must supply the power required for all operating modes of a device, while the shared power supply mode of multiple Ethernet power supply devices can be adjusted according to the average power utilization rate – just like POTS that has been used for many years phone technology. This greatly reduces the amount of power consumption of the switching power supply during idle periods. The saved power usually accounts for 10%-20% of the highest power supply load. When it is necessary to provide more power, additional power supply equipment can be installed in the Ethernet switch and Ethernet intermediate equipment, so as to ensure that the power supply is adjusted according to the growth needs of the business.

Energy Efficient Power over Ethernet (EEPoE): Advanced Power over Ethernet Energy Saving Technology

With the development of Power over Ethernet technology, from the level of power supply power is quite low (12.95 watts per port) to the level of power supply power reaching 25.5 watts. During this time, power loss on Ethernet cables increases exponentially. About 4.5 watts/port of power is lost in CAT5, CAT5e, CAT6, CAT6A cables, and after 100 meters encounters the worst loop resistance problem on 25,000 meters of cable length (for example, the cable transmission efficiency is only 25.5 /30, equivalent to 85% transfer rate). Even if 54 volts were applied instead of 50 volts, the transfer efficiency would not exceed 87%. Remember, traditional Energy Efficient Ethernet typically saves no more than one watt per connection. More power needs to be saved to deal with the 4.5 watts per connection lost due to inefficient PoE transmission.

When transmitting power over the same 25-ohm cable, the new energy-saving Power over Ethernet technology can increase the transmission efficiency to 94% by using IEEE802.3at-compliant technology in synchronized four-pair wires. When using simultaneous four-pair wires, the power requirements of the equipment can be met using all available wires. For example, in IEEE802.3at-2009Type 2 system with 24 ports (transmitting power up to 25.5 watts per port), more than 50 watts of power can be saved.

In particular, reference switch system products incorporating Energy Efficient Ethernet technology and Energy Efficient Power over Ethernet technology have demonstrated significant power savings. Please review the form below:

Power saved by technology Saved time Ethernet connections sold per year

Power-efficient Ethernet technology (PoE) over GbE ~1 watt/connection 200 million connections during idle periods and growing

Energy Efficient Power over Ethernet (EEPoE) on 3af about 0.6 watts/connection 40m once powered on and growing

Energy Efficient Power over Ethernet (EEPoE) on 3at about 2.1 watts/connection 30m once powered on and growing

Total electrical energy savings 3.13 watts/connection

Note: Energy-saving Power over Ethernet technology does not require replacement of electrical equipment. As a result, immediate power savings can be achieved simply by upgrading switches or PoE intermediate devices.

Applying Innovative Technology to Power over Ethernet Systems

In order to realize the advanced EEPoE technology, Marvell and Microsemi have adopted unique microprocessor technology embedded in the Marvell Prestera DX4100 and DX2100 product series. This innovative approach provides a platform for customers. This platform will help customers build cost-effective and powerful network equipment. The device is embedded with an offload selector for the main CPU. With the integrated main CPU, Marvell Prestera DX4100 and DX2100 microprocessors are equipped with an additional embedded microcontroller, Marvell Dragonite. The controller is capable of running lightweight, standalone applications. Microsemi EEPoE management software can now run on Dragonite microcontrollers to help customers improve the performance of Power over Ethernet systems while reducing the overall system cost by 15%.


With the approval of the IEEE802.3az standard in September 2009, Power over Ethernet (PoE) technology can already save more power. Power over Ethernet technology provides power to devices over an Ethernet cable fabric that can also carry data. This brings great benefits. This way, we no longer need to install costly AC outlets. When deploying equipment, there is no need to install cables, and it is only necessary to realize energy-saving automation according to the opening, closing and transmission status of the equipment.

Combined with the Energy Efficient Ethernet (EEE) standard, Power over Ethernet (PoE) will bring even greater value. The two cannot be separated, but leverage each other in a complementary manner. Technology providers such as Marvell and Microsemi are collaborating to develop innovative energy-efficient PoE solutions (such as switches, Ethernet middleware), thereby helping OEMs to provide more cost-effective and environmentally friendly products – the entire industry will Will benefit from this in the near future and in the future.

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