PAUSE Power Cycle: A New Backwards Compatible Method to Reduce Energy Use of Ethernet Switches

Because of economic and environmental reasons, reducing the energy consumption of IT equipment and other devices connected to the Internet has become a major issue. Most IT equipment is left powered-on 24/7 to provide full and fast connectivity to users. As of 2000, there were approximately 95,000 Ethernet switches deployed in the U.S. alone consuming approximately 3.2 Terawatt hours of electricity [6]. It is well recognized that the vast majority of the links in LAN switches operate at much lower levels of utilization than their data rate [7]. Several consortium-level initiatives are now underway to reduce energy use of IT equipment [13, 15]. Standards initiatives for reducing energy used by networks include IEEE 802.3az Energy Efficient Ethernet [10]. The Ethernet Alliance played a major role in kicking off the EEE effort with the publication of a White Paper on Adaptive Link Rate [9]. In the commercial arena, D-Link is now offering " Green Ethernet " switches that use variable link power as a function of link length and turn off unused ports [14]. Energy efficient Ethernet switches can provide significant global savings in electricity consumption. The IEEE 802.3az task force (Energy Efficient Ethernet) is exploring methods for scaling Ethernet link rate as a function of utilization to save energy. IEEE 802.3az is studying methods that require both end points of an Ethernet link to implement new mechanisms and policies, thus these methods cannot achieve energy savings with existing Ethernet devices. In this white paper , a new backwards compatible method for achieving energy savings in Ethernet switches is designed, emulated, and evaluated. This new method is called PAUSE Power Cycle (PPC). PPC uses 802.3 PAUSE flow control to cycle Ethernet links between ON and OFF (PAUSEd) states. Major energy savings can be achieved if electrical components are powered-off during the times the link is OFF. Preliminary experimental results show that PPC with a cycle time of 50 ms ON and 50 ms OFF has little or no perceivable effects to users of popular Internet applications such as web browsing, file downloading, real-time video, and play-back video (e.g., YouTube). Estimates show that energy savings in the range of $132 million dollars per year in the U.S. can be achieved if PPC is adopted.