【正文】 導(dǎo)航．北京:人民郵電出版社，2006.[23] 余永權(quán)，汪明恩，黃英編．單片機(jī)在控制系統(tǒng)中的應(yīng)用．北京:電子工業(yè)出版社，2003.[24] 李剛，林凌，姜葦中數(shù)休閑51系列單片機(jī)系統(tǒng)設(shè)計(jì)與應(yīng)用技巧．北京:北京航天航空大學(xué)出版社，2004.[25] [26] 張義和．ProtelDXP電路設(shè)計(jì)大全．北京:中國鐵道出版社，2005.[27] 程顯．精通Protel DXP電路設(shè)計(jì)．北京:清華大學(xué)出版社，2004：3784.[28] 韓潔瓊，曾牌，余永權(quán)，李太．四層電路板的PCB設(shè)計(jì)．單片機(jī)與嵌入式系統(tǒng)應(yīng)用，:1514. 附錄A 英文文獻(xiàn)及其翻譯外文文獻(xiàn)：Saving Energy in LAN Switches:New Methods of Packet Coalescing for Energy Efficient Ethernet Mehrgan Mostowfi and Ken Christensen Department of Computer Science and Engineering University of South Florida Tampa, Florida {mostowfi, christen}@ Abstract—Small or home office (SOHO) Ethernet LAN switches consume about 8 TWh per year in the . alone. Despite normally low traffic load and numerous periods of idleness, these switches typically stay fully poweredon at all times. With the standardization of Energy Efficient Ethernet (EEE), Ethernet interfaces can be put into a Low Power Idle (LPI) mode during idle periods when there are no packets to transmit. This paper proposes and evaluates a new EEE policy of synchronous coalescing of packets in network hosts and edge routers. This policy provides extended idle periods for all ports of a LAN switch and thus enables energy savings deeper than in the Ethernet PHY only. We evaluate our method using an ns2 simulation model of a LAN switch. We show that our method can reduce the overall energy use of a LAN switch by about 40%, while introducing limited and controlled effects on typical Internet traffic and TCP. KeywordsEthernet switch。 synchronized coalescing。 Energy Efficient Ethernet。 green InternetI. INTRODUCTION Networked electronic devices consumed almost 4% (150 TWh) of all the electricity in the . in 2008, about 13% (20 TWh) of which was consumed by net work equipment such as network switches and routers [22]. Ethernet, as the dominant wireline technology for LANs, constitutes a significant portion of the energy use of puter networks. The most recent advance in reducing the energy consumption of Ethernet is Energy Efficient Ethernet (EEE) which was standardized as IEEE Std in September 2010 [12]. Products that use EEE are beginning to ship in mid to late 2011. EEE enables an Ethernet link that is idle to exit Active mode and enter a Low Power Idle (LPI) mode. The power used in LPI mode is significantly less than in Active mode since some ponents of the physical layer (PHY) can be powered off. The IEEE standard does not describe a policy for entering and exiting LPI. A simple policy would be to enter Active mode when packets are queued in the transmit queue in the interface and enter LPI mode when the queue is empty. Such a policy has been found to be ineffi cient (that is, wasteful of energy) due to excessive transitions between the Active and LPI modes [25]. Each transition incurs a delay and energy use. A policy to batch, or coalesce,packets was proposed and explored by Christensen et al. in 2010 [6]. Coalescing improves the energy efficiency of Ethernet interfaces in hosts as well as in Ethernet switches. The overall energy consumption of a switch is reduced by EEE as a result of the reduction in energy consumption of individual interfaces of the switch. However, we believe that energy savings by EEE can go beyond the savings in individual interfaces if all the switch ports enter LPI mode at the same time, or synchronously. Synchronized LPI periods provide the opportunity for additional ponents of the switch to power down since it would be certain that there are no packets in any port buffer, or within the switch fabric, that need to be forwarded. In synchronized coalescing the control of when to coalesce and for how long is moved to the switch (from the host interfaces) and the coalescing periods are synchronized on all the ports of the switch. The target switches for our synchronized coalescing method are the ones mostly used in households and small offices. This type of switch, which are referred to as SOHO (small or home office) switches hereafter, typically includes 4 to 10 ports and cost less than $100. Two factors motivated us to propose synchronized coalescing. The first is the typi cal low utilization of switches in general [9]. The second is that although SOHO Ethernet switches consume only a small amount of energy individually, the number of them deployed in the country is so high that it makes their consumption significant and even a small savings per switch would add up to a significant overall savings. Using a KillAWatt power meter, the power use of a Linksys EG005W Gigabit Ethernet switch with 4 connected active links was measured as 10 W. We estimate that the current consumption of SOHO Ethernet switches is approximately TWh/year based on the number of housing units in the . [26], assuming that about 70% have an Ethernet switch installed, and that each switch is powered on all the time. At the current average electricity cost ($) this is a total of about $790 million per year in electricity use. While current Ethernet links and switches are mostly 100 Mb/s and 1 Gb/s, we envision that they are likely to evolve to 10 Gb/s in the near future for several reasons including, 1) everdecreasing prices [20], 2) fast adoption by vendors [18], and 3) increasing bandwidth requirements of multimedia applications within households (for example audio/video transfer between storage device and player, and LANbased multiplayer video games). The contributions of this paper are the proposal and explanation of synchronized coalescing and evaluation of its performance tradeoffs and effects on typical Internet traffic and TCP through simulation. The remainder of this paper is organized as follows. Section II reviews EEE and previous work that has been done in policies to control EEE. Section III presents a microlevel study of the power use of SOHO Ethernet switches and the opportunity of powering down individual ponents. Section IV explains the ne