Power over Ethernet (PoE): An energy-efficient Ethernet solution

Introduction: Ethernet switch power consumption

In modern network architectures, IT and data center managers are looking for green options to reduce power consumption in Ethernet switches, routers, and server equipment. This requires more environmentally friendly products on the market to reduce operating costs. For example, in 1993, the total Internet traffic for the whole year amounted to several hundred terabytes. And 17 years later in 2010, the Internet traffic per second reached several hundred terabytes. In fact, today, more than 50% of data center operating expenses are used for equipment cooling, that is, to provide electricity for 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.

Network devices that support the Power over Ethernet (PoE) protocol are out of touch. As a result, in the network market, device power consumption is growing rapidly, especially for devices with high-frequency application processors.

Considering that more than 300 million Ethernet switch ports are sold each year, the power loss caused by idle lines has become a significant and widespread problem that deserves attention. The IEEE Energy Efficient Ethernet specification was created with the goal of significantly reducing the power consumption of the more than 600 million Ethernet ports sold each year. However, this specification does not address the fact that when Ethernet power systems are deployed, the vast majority of power loss occurs in the Ethernet power delivery subsystem - not in the data portion.

In 2010, nearly 70 million Ethernet power switch ports were shipped. This is a key concern for enterprises deploying Ethernet-powered IP phones, WLAN networks, IP security applications, and other applications. For example, a standard 48-port Ethernet switch only needs to distribute 50W to 80W of power to traditional Ethernet switches and transceiver ICs. However, the switch needs to supply 370W to 740W of power to the Ethernet power system. This 8:1 comparison factor means that a small improvement in the power efficiency of the Ethernet power system can greatly improve the overall power efficiency of the Ethernet switch.

Traditional Energy Efficient Ethernet (EEE)

In order to cope with the increasing power consumption of Ethernet switches, IEEE has developed and approved the 802.3az standard. This standard is called Energy Efficient Ethernet (EEE). This 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 concept of disconnecting the power supply during periods of low utilization or idleness, and restoring the power supply during periods of data transmission. This concept is based on the well-known fact that client and server Ethernet connections in a standard network environment are idle most of the time. Peak data traffic only occurs occasionally.

EEE specifies a Low Power Idle (LPI) protocol. This protocol controls the signaling at both ends of the physical connection to enable rapid adjustment of the power saving mode of the connected devices - including turning off the power and stopping the system's data transmission and reception functions during periods of no data transmission. In addition, the Energy Efficient Ethernet standard specifies another protocol. This protocol keeps the operating parameters of the Ethernet physical layer system in Low Power Idle (LPI) mode updated at all times, thereby maintaining a stable connection and preventing the connection from being disconnected. In addition, the Energy Efficient Ethernet standard specifies a signaling protocol on one side. This protocol indicates when the physical connection is needed and enables rapid connection recovery. As a result, at a high level of Ethernet physical layer technology, the Low Power Idle (LPI) application can save one watt of power for each Ethernet connection. However, the Energy Efficient Ethernet standard does not address the problem of Ethernet power consumption or how to reduce energy consumption.

Energy-saving mechanism of Power over Ethernet (PoE) system

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

In multi-port devices, data also proves the advantages of Ethernet power supply. 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 telephone technology that has been used for many years. This greatly reduces the power consumption of the switched power supply during idle periods. The power saved usually accounts for 10%-20% of the maximum power supply load. When it is necessary to provide more power, additional power supply devices can be installed in Ethernet power supply switches and Ethernet intermediate devices to ensure that the power supply is adjusted according to the growth needs of the business.

Energy-efficient Ethernet Power (EEPoE): Advanced Ethernet Power-saving technology

As Power over Ethernet has evolved, from fairly low power levels (12.95 watts per port) to power levels as high as 25.5 watts. In the intervening period, the power losses on Ethernet cables have increased exponentially. About 4.5 watts/port are lost on CAT5, CAT5e, CAT6, CAT6A cables, and after a hundred meters, the worst-case loop resistance of a 25,000 meter cable is encountered (for example, the cable transmission efficiency is only 25.5/30, which is equivalent to 85% transmission rate). Even if 54 volts are applied instead of 50 volts, the transmission efficiency will not exceed 87%. Remember, traditional Energy Efficient Ethernet generally saves no more than one watt per connection. To counteract the 4.5 watts of power loss per connection caused by inefficient Power over Ethernet transmission, we need to save more power.

When transmitting power on the same 25-ohm cable, the new energy-saving Ethernet power supply technology can increase the transmission efficiency to 94% by using the same IEEE802.3at compatible technology in the synchronous four-pair line. When using the synchronous four-pair line, the power supply needs of the equipment can be met by utilizing all the available wires. For example, in the 24 ports of the IEEE802.3at-2009 Type 2 system (each port transmits 25.5 watts of power), more than 50 watts of power are saved.

In particular, the reference switch system products that combine Energy Efficient Ethernet technology and Energy Efficient Ethernet Power Technology have proven to save a lot of power. Please see the table below:

Power saved by technology Time saved Number of Ethernet connections sold per year

Energy Efficient Ethernet (PoE) over GbE About 1 watt per connection when connections are idle 200 million and growing

Energy Efficient Ethernet Power over 3af (EEPoE) ~0.6W/connection once power is on 40m and growing

Energy-efficient Ethernet Power over 3at (EEPoE) about 2.1 watts/connection once power is on 30m, and growing

Total power saving 3.13 watts/connection

Note: Energy-efficient PoE technology does not require the replacement of power-consuming devices. Therefore, energy savings can be achieved immediately by simply upgrading switches or PoE middleware.

Applying innovative technologies to Ethernet power systems

To achieve advanced EEPoE technology, Marvell and Microsemi use unique microprocessor technology embedded in the Marvell Prestera DX4100 and DX2100 product families. 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, the Marvell Prestera DX4100 and DX2100 microprocessors are equipped with an additional embedded microcontroller Marvell Dragonite. The controller is capable of running lightweight, independent applications. The current Microsemi EEPoE management software can run on the Dragonite microcontroller, helping customers improve Ethernet power supply system performance while reducing the overall cost of the system by 15%.

Summarize

With the approval of the IEEE802.3az standard in September 2009, Power over Ethernet (PoE) has made it possible to save even more power. Power over Ethernet provides power to devices through the same Ethernet cable infrastructure that can also transmit data. This brings great benefits. In this way, we no longer need to install expensive AC interfaces. When deploying equipment, there is no need to install cables, just realize energy-saving automation based on the device's on, off and transmission status.

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