一種可以大幅削減以太網(wǎng)能耗的以太網(wǎng)標(biāo)準(zhǔn)正在獲得廣泛的支持,預(yù)計在九月早些時候,基于這個標(biāo)準(zhǔn)的草案可以用于指導(dǎo)相關(guān)的產(chǎn)品設(shè)計,這種所謂的能效以太網(wǎng)(Energy-efficient Ethernet)的研究組已經(jīng)成立,致力于這種能效以太網(wǎng)在100Mbit和Gbit級別芯片上的應(yīng)用。

主導(dǎo)IEEE 802.3az的官方研究機(jī)構(gòu)Lawrence Berkeley國家實驗室的研究人員Mike Bennett說:“我希望我們能夠在九月份的會議上形成一項能夠指導(dǎo)人們應(yīng)用的草案盏混∈澜ⅲ”

研究組也已經(jīng)收到了一項所謂的可以應(yīng)用于100Mbit和Gbit的低功耗空轉(zhuǎn)提案,基于這項Intel主導(dǎo)的提案,以太網(wǎng)芯片可以在沒有數(shù)據(jù)發(fā)送時將物理層設(shè)置為休眠模式。

一旦物理層處于休眠模式,工程師可以決定是否系統(tǒng)的其他部分也置于低功耗的狀態(tài),Bennett指出:“我認(rèn)為挑戰(zhàn)恰恰來自于人們?nèi)绾胃鶕?jù)物理層的狀態(tài)關(guān)斷系統(tǒng)的其他部分焰薄∧弥睿”

盡管如此,也有一些工程師們認(rèn)為這種低功耗空轉(zhuǎn)的方法可能引入額外的緩沖和無法接受的網(wǎng)絡(luò)抖動和響應(yīng)時間,還有一種由Aquantia和Broadcom主導(dǎo)的提案稱作物理層子集,可以將10Gbit的鏈接縮放至單獨的Gbit通道,這樣也可以節(jié)省功耗。

所有這些提案都需要對物理層和MAC層的構(gòu)成作一些改變,這些改變會帶來供應(yīng)商的頻繁的產(chǎn)品刷新,低功耗空轉(zhuǎn)方案的提案人,Intel的網(wǎng)絡(luò)工程師Robert Hayes指出:“雖然不會有大的硬件改動,但這些改動還是客觀存在的塞茅∧堵耄”

一位Broadcom的執(zhí)行主管在最近的的采訪中指出就網(wǎng)絡(luò)設(shè)備來說物理層子集方案更優(yōu),同時他也補(bǔ)充說低功耗空轉(zhuǎn)方案更適合于電腦服務(wù)器和客戶端。

盡管如此,Hayes指出惠普網(wǎng)絡(luò)組和思科系統(tǒng)的工程師們都表示了對低功耗空轉(zhuǎn)方案的支持,同物理層子集方案不同的是,它允許工程師們有更大的自由度可以關(guān)斷系統(tǒng)里的一部分功能野瘦。

“例如如果我們知道線上沒有數(shù)據(jù)我們可以關(guān)斷PCI Express總線,存儲器控制器描沟。甚至是部分主處理器” ,Hayes指出說:“這能夠帶來實實在在的功耗降低,一些開關(guān)供應(yīng)商也同意這樣的處理方法.”

.3az委員會會在5月或者7月的會議上對這兩種方案的優(yōu)劣進(jìn)行討論,目前看起來在下周的會議上不太可能有新的提案出現(xiàn),這也是新的技術(shù)觀點可以提案的最后一次會議。

研究組也會審閱一批針對10Mbit和背板以太網(wǎng)的提案鞭光。

研究組還可能提案一種降低10Mbit以太網(wǎng)傳輸信號振幅的方法,這些信號原先是針對3類電纜的設(shè)計,目前5類電纜可以處理這些低振幅傳輸信號,因此可以節(jié)省功耗吏廉。

研究組將分別評估低功耗空轉(zhuǎn)方案和物理層子集方案在Gbit和10Gbit背板以太網(wǎng)鏈接上的應(yīng)用,下周的會議上將對兩種技術(shù)的折衷進(jìn)行討論,Bennett希望到九月末會議之前能夠就所有目前遇到的顯著問題形成結(jié)論。

.3az研究組作為802.1委員會的代表組織致力于更高層網(wǎng)絡(luò)協(xié)議的討論,.3az研究組的目標(biāo)是建立起這樣的機(jī)制,當(dāng)一種應(yīng)用或者操作系統(tǒng)需要在低功耗環(huán)境中運行時,這些物理層的節(jié)省功耗的技術(shù)對于上層協(xié)議不可見惰许。

研究組開始試圖通過在無網(wǎng)絡(luò)傳輸要求時降低傳輸速率至10Mbit的方法降低功耗,不過后來測試表明速率由低到高的切換時間(長達(dá)20毫秒)可能會導(dǎo)致無法接受的丟包,特別是在音頻數(shù)據(jù)交換中迟蜜。

作為Lawrence Berkeley實驗室更廣泛研究行動的一部分,.3az研究組致力于在大范圍的網(wǎng)絡(luò)和消費電子系統(tǒng)中降低能耗。

一位Lawrence Berkeley的研究人員估計IEEE的研究努力在美國每年將會節(jié)約4億5千萬美元的能耗費用,有趣的是,這其中的大部分——2億美元將來自家庭電腦,1.7億美元來自于辦公室,另外8千萬美元來自于數(shù)據(jù)中心,研究人員還估計通過在低數(shù)據(jù)交換時降低數(shù)據(jù)率會降低能耗,其中在Gbit卡接口可以降低1.5瓦的功率,10 Gbit卡可以降低10瓦忧绊。

翻頁查看英文原文:

Energy-efficient Ethernet standard gains traction

A standard to slash the power consumption on Ethernet networks is gaining traction and could be in a draft form suitable for designing products as early as September. The so-called energy-efficient Ethernet group has already settled on an approach for use on 100 Mbit and Gbit chips.

"I hope we can come out of our meeting in September with [a draft] people could implement," said Mike Bennett, a researcher at Lawrence Berkeley National Lab chairing the effort officially known as IEEE 802.3az.

The group has already accepted a so-called low-power idle proposal for use with 100 Mbit and Gbit connections. Under the proposal, led by Intel, Ethernet chips with no data to send would be able to put the PHY into a sleep mode.

Once the PHY is in sleep mode, engineers could decide whether they wanted to put other parts of their systems into a low power state. "I think a competitive edge could come from how people turn things off in a system based on what's happening at the PHY," said Bennett.

However, at 10 Gbit rates, some engineers have suggested the low-power idle approach could require additional buffers or might introduce jitter or latency that would be unacceptable. An alternate proposal from startup Aquantia and Broadcom, called subset PHY, calls for scaling a 10Gbit link down to a single Gbit channel to save power.

Both proposals will require some changes in the PHY and MAC components which vendors would probably make during regular product refresh cycles. "There are not huge hardware changes, but there are some," said Robert Hayes, an Intel networking engineer who helped define the low-power idle proposal.

A Broadcom executive said in a recent interview that the subset PHY approach is better suited to networking equipment. The low-power idle approach is geared more closely to the interests of computer servers and clients, he added.

However, Hayes said engineers from Hewlett-Packard's networking group as well as Cisco Systems have shown support for low-power idle. Unlike the subset PHY approach which maintains a Gbit connection, it allows engineers to turn off a range of functions in their systems, he said.

"If we know we don't have data coming down the wire we can turn off a PCI Express bus, memory controller and maybe even parts of a host processor," said Hayes. "That leads to substantial savings in a server and some switch vendors are saying the same thing," he added.

The .3az committee needs to debate the merits of the two approaches at meetings in May or July. It is unlikely any new proposals will come up at next week's meeting, the last meeting where new technology ideas can be proposed.

The group is also looking at proposals for 10 Mbit and backplane Ethernet.

The group is likely to propose lowering the transmit amplitude for 10 Mbit Ethernet signaling originally designed for the Category 3 cabling of its time. Today's Category 5 cables can handle lower transmit amplitudes, saving power.

Separately the group is looking at ways to apply low-power idle or subset PHY techniques to Gbit and 10 Gbit backplane Ethernet links. The trade offs for backplanes between the two techniques are expected to be debated at the meeting next week. Bennett said he was hopeful a decision on all the outstanding issues could be reached by the end of the September meeting.

The .3az group held discussions with representatives of the 802.1 committee on higher player protocols. The .3az goal is to create mechanisms that would let higher layer protocols override energy saving techniques in the PHY if an application or operating system needed to choose performance over low power.

The group initially explored the idea of ratcheting speeds down to as low as 10 Mbits/s when there was no network demand. However, tests indicated the switching time of as much as 20 milliseconds from low to high speed could cause unacceptable packet losses, especially for audio traffic.

The .3az work is in part a spin out of a broader initiative at Lawrence Berkeley Lab to lower energy consumption across a wide range of network and consumer systems.

One Lawrence Berkeley Labs researcher estimated the IEEE effort alone could save $450 million in energy costs a year just in the U.S. Interestingly, the brunt of the savings--$200 million--could come from home computers, with another $170 million from offices and $80 million from data centers. The researcher estimated that a Gigabit interface card could shave up to 1.5 W off its power consumption and a 10-Gbit card up to 10 W by scaling back data rates at times of low traffic.

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