Gigabit Ethernet
Ethernet link
The 802.3az Energy Efficient Ethernet (EEE) standard from the IEEE promises to save billions in energy costs. With virtually every computer networked in some way, the energy usage of the networking equipment is incredibly large. That includes the network interfaces in PCs and laptops to the servers in data centers that manage and implement the networking functions.
Since most networks use some form of Ethernet, changes to the basic Ethernet standard 802.3 could produce viable savings. Over the past several years, the IEEE 802.3az Task Force group has produced a standard that is expected to reduce not only energy costs but also the overall carbon footprint of energy sources. Broadcom is one of the first companies to offer chips that implement the standard.
The Need for Energy Efficiency
According to the ITU World Summit on the Information Society, electricity demand by the networking sector for industrialized countries is between 5% and 10% of total electricity demand. About 50% of this electricity is wasted by equipment that is powered on, but idle.
Ethernet sends data in bursts that are often seconds to hours apart. Based on analyses of local-area network (LAN) link utilization, users are only connected 1% to 5% of the time they’re powered up. The IEEE 802.3az amendment to IEEE 802.3 defines mechanisms and protocols designed to reduce the energy consumption of network links during periods of low utilization by transitioning interfaces into a low-power state.
EEE is designed to wake up and transmit data as fast as possible and then return to a low-power sleep state. Called lower-power idle (LPI), these hardware features plus new control policies let the network equipment power down most of the media access controller (MAC) functions and some physical-layer (PHY) operations for significant power savings. The standard also communicates state and control information over the network to enable or disable the various energy-efficient modes of operation. And, it does this without interrupting the network connection.
Ethernet dominates network technology, with billions of interfaces deployed. It is used in environments ranging from high-performance links at the Internet core to basic home networks. Ethernet continues to meet the ever-increasing demand for higher network speeds, but the outcome has been driving the energy consumption of network products higher and higher.
Today, energy savings is the number one job of IT managers everywhere. IEEE 802.3az, which was approved on September 30, 2010, puts into motion the process of developing new energy-efficient networking products. The standard will eventually reduce energy consumption in network-attached devices, network routers and switches, computers, and printers.
IEEE 802.3az uses the Link Layer Discovery Protocol (LLPD) from IEEE P802.1AB and Type, Length, Values (TLVs) from IEEE 802.3bc. This enables system designers to save more than the Ethernet interface energy by allowing the communication of energy-utilization information between link partners without interrupting the network link.
The IEEE estimates that when 802.3az-compliant products have been fully deployed in new and existing Ethernet networks, the power savings in the U.S. alone can reach 5 terawatt-hours per year, or enough energy to power 6 million 100-W light bulbs. Another estimate predicts that if EEE were adopted at a 100% rate in the U.S. alone, energy savings could yield as much as $470 million per year. And that doesn’t include any savings for cooling or related equipment.
Incidentally, EEE is specified primarily for copper PHYs including 100BASE-TX, 1000BASE-T, 10GBASE-T, 10GBASE-KR, 10GBASE-KX4, and 1000BASE-KX. EEE is not specified for optical PHYs, but that may be a future addition to the standard.
Making EEE Happen
Broadcom’s extensive new portfolio lets engineers begin adopting EEE. It gives designers of new Ethernet gear a wide range of options for implementing the new EEE standard. Its chips range from entry-level unmanaged switches to enterprise and metro-class switches; single, quad, and octal Gigabit Ethernet (GbE) PHYs; dual and quad 10GbE PHYs; 10/100 and 1GbE controllers; and 10GbE converged network interface controllers (C-NICs).
These EEE-compliant products offer energy savings of up to 70% or greater over PHYs without EEE. They also provide designers with silicon and software that enable faster deployment of energy-efficient network products.
The BCM54680E PHY chip is an eight-port 10/100/1000BASE-T Gigabit copper transceiver with full 802.3az support (Fig. 1). The eight transceivers are integrated on a single CMOS chip. It targets higher-density switches for enterprise and data-center applications. Also, it has SGMII interfaces and exceeds the IEEE spec for noise cancellation and transmission jitter, providing consistent and reliable operation over the incredibly wide range of existing cable installations.
The BCM54680E is based on Broadcom’s proven DSP technology that combines digital adaptive equalizers, analog-to-digital converters (ADCs), phase-locked loops (PLLs), line drivers, encoders, decoders, echo cancellers, crosstalk cancellers, and other circuitry. The chip supports native EEE MACs as well as legacy non-EEE MACs by using Broadcom’s AutogrEEEn mode. Internal cable plant diagnostics that detect cable plant impairments. Other features include programmable LED outputs, low-EMI (electromagnetic interference) emissions, and on-chip thermal and voltage monitors.
Braodcom’s complete line of ICs that support EEE includes six Ethernet controllers, three switches, and 11 different PHYs. For example, the BCM7781 Gigabit Ethernet controller targets PC applications. It integrates the MAC and PHY on a single chip to provide wired network connectivity for desktop, notebook, and netbook products.
Broadcom’s new silicon portfolio also goes beyond the EEE standard with its own Energy Efficient Networking (EEN) initiative, which enables enhanced energy savings beyond what is inherent in the EEE standard (Fig. 2). This gives designers a faster time-to-market for their EEE-compliant solutions.
As part of the EEN initiative, Broadcom has developed its proprietary AutoGrEEEn technology to facilitate the adoption of EEE and provide a faster migration path for legacy networking equipment. AutoGrEEEn technology implements the EEE standard directly into Broadcom PHYs and permits them to be in EEE mode when interfacing with non-EEE enabled MAC devices without requiring changes to those devices. This innovation allows customers to make existing network equipment EEE-compliant by simply changing the PHY devices.
