以太網(wǎng)聯(lián)盟主席、戴爾首席技術官辦公室以太網(wǎng)傳播總負責人 John D’Ambrosia

 

2013年，以太網(wǎng)行業(yè)迎來了以太網(wǎng)40歲生日以及以太網(wǎng)標準誕生30年。以太網(wǎng)的速度進展一直是可預測的——以10倍的增量從最初的10Mb/s到100Mb/s，到1Gb/s，再到10 Gb/s，這幾乎無可爭議。不過，40GbE和100GbE的同時推出有效終結了這一傳統(tǒng)。

 

40GbE和100 GbE的發(fā)展基于一個根本假設，即：計算與網(wǎng)絡帶寬的增長率存在相當大的差異，因此兩種速度具有同時存在的必要性。在計算領域，帶寬能力每24個月翻一倍，而網(wǎng)絡應用程序則每18個月翻一倍。網(wǎng)絡這種可預測的增長率后來同樣被IEEE 802.3以太網(wǎng)帶寬評估特別小組確認。據(jù)其預測，平均下來，到2015年，網(wǎng)絡必須支持TB每秒的能力，到2020年，必須支持10TB每秒的能力。

 

下圖顯示了這兩個應用領域可預測的帶寬能力，這是由IEEE 802.3更高速以太網(wǎng)研究小組(后來發(fā)展成為開發(fā)40 GbE和100GbE的任務小組)在2007年底所做的預測。那么到了2013年，這一預測的準確程度如何呢?

 

 

圖注：較早時候的以太網(wǎng)帶寬發(fā)展預測

 

在現(xiàn)實中，支持和反對這一預測的說法都是可以成立的，但是否認同其精確度卻取決于做出這一預測的思考角度。如果從電信運營商的角度來看，人們可能會認為這相當準確，因為100GbE在電信運營商領域產生了極大的影響，并且正在健康發(fā)展。但是在數(shù)據(jù)中心領域，卻可以得出反對這一預測的結論，因為100GbE并沒有在數(shù)據(jù)中心網(wǎng)絡中產生同樣大的影響——相反，40 GbE端口卻在這里穩(wěn)步健康發(fā)展。

 

這種新興部署場景提出了一些需要考慮的問題：首先，為什么數(shù)據(jù)中心網(wǎng)絡中部署的是40GbE，而不是100GbE?首先應該注意的是：數(shù)據(jù)中心之所以部署40GbE，是因為通過將4個10 Gb/秒運行的4個通道捆綁可以實現(xiàn)總共40 Gb/秒的聚合鏈路。這是一個重要的發(fā)現(xiàn)，因為40GbE端口與并行導體或光纖結合使用，就可以實現(xiàn)更高的四倍密度10GbE端口配置。

 

這就提出了一個有趣的問題——我們是否應將整個數(shù)據(jù)中心看作一個計算應用呢?如果我們考慮到40GbE部署的時機，并且看一看上圖，就會發(fā)現(xiàn)，數(shù)據(jù)中心帶寬需求似乎證明了那些最初認為40GbE適用于服務器的想法。如果我們接受這種推理，那么按照計算應用預測，意味著我們將在2017年~2018年看到數(shù)據(jù)中心部署100GbE。這一現(xiàn)象還提出了一個關于突破性功能的重大問題，這將對400G以太網(wǎng)的發(fā)展產生影響。

 

因此，當我們慶祝以太網(wǎng)40歲生日的活動進入尾聲時，顯然會得出結論，以太網(wǎng)將繼續(xù)向前演進，尤其是在速度提升方面。這一判斷提出了許多需要思考的問題，整個行業(yè)仍需要注重達成共識，以此推進以太網(wǎng)向前發(fā)展。

 

 

 

英文原文：

 

 

 

The State of Ethernet's Rate

 

by John D’Ambrosia, Chair of the Ethernet Alliance,Chief Ethernet Evangelist, Dell Networking CTO Office

 

In 2013 the Ethernet industry has been celebrating 40 years of Ethernet and 30 years of Ethernet standards. Ethernet's rate progression had been fairly predictable, 10x increments from its initial 10 Mb/s to 100 Mb/s to 1 Gb/s to 10 Gb/s with little to no controversy. The simultaneous introduction of 40 GbE and 100 GbE effectively ended this legacy.

 

The development of 40 GbE and 100 GbE was based on the fundamental assumption that the growth rates between computing and networking were sufficiently different to justify the two rates. For the computing space, bandwidth capabilities were doubling every 24 months, while network applications were doubling every 18 months. The predicted growth rate for networking was later re-confirmed by the IEEE 802.3 Ethernet Bandwidth Assessment Ad hoc, which forecasted that on average, networks would need to support terabit per second capacities by 2015 and 10 terabit per second capacities by 2020.

 

Figure 1 shows the predicted bandwidth capacities of the two application spaces, which was made in late 2007 by the then IEEE 802.3 Higher Speed Ethernet Study Group (which would later go on to become the Task Force that developed 40 GbE and 100GbE). So in 2013 how accurate was this prediction?

 

 

Figure 1- Past Ethernet Projections

 

In reality, arguments for and against this prediction can be made, but that accuracy is truly dependent upon the perspective by which the prediction is being considered. If one looks at this prediction from the service provider perspective, one might argue that it was a fairly accurate, as 100GbE is having a big impact in the service provider space and enjoying healthy deployment. However, in the data center space, arguments against this prediction could be made, as 100GbE is not having the same impact in data center networks, which instead is seeing healthy deployment of 40 GbE ports.

 

This emerging deployment scenario raises a lot of issues for consideration. First, why is 40 GbE seeing deployment in data center networks, instead of 100GbE? The first thing that should be noted is that the 40GbE that is seeing deployment in the data center is based on 4 lanes running at 10 Gb/s to achieve an aggregate of 40 Gb/s. This is an important observation, because the 40GbE ports are being used with parallel conductors or fibers to achieve a higher quad density 10GbE port configuration.

 

This raises an interesting question – should we be looking at the entire data center as a compute application? If we consider the timing of 40GbE deployment, and we look at Figure 1, then the bandwidth requirements would seem to mirror those initially thought to be just for the servers. If we accept that reasoning, then following the predictions of the compute application forecast means we will see 100GbE deployed in the data centers in the 2017 to 2018 time frame. It also raises the question regarding the significance of breakout functionality, which would have implications for the development of 400 Gigabit Ethernet.

 

So as we come to the end of celebrating Ethernet's 40th Anniversary, it is clear that Ethernet will continue its evolution forward, particularly in respect to higher speeds. And while this perspective has raised many questions for consideration, the industry will need to focus on reaching consensus in order to drive this evolution forward.