Green Technology

What is EEE or Energy Efficient Ethernet?


Nowadays, it’s impossible to imagine a world without the internet. But what makes the internet possible are millions of billions of network connections all over the world. Most of these connections are done via the ethernet. These connections use a lot of energy to maintain. In fact, back in 2005, it is estimated that these connections use 5.3 terrawatts of electricity in an hour. The EPA, trying to make computer components as energy efficient as possible, realized the problem. So they asked the IEEE for advice regarding an energy efficient standard for the ethernet. And that’s how the Energy-Efficient Ethernet or EEE was born.

At the most common ethernet speed (100 Mbit/s and higher), the connection is always on, and energy is always being spent maintaining the link speed whether you are using it or not. This energy, while minuscule adds up quite a bit. After all, routers and switches tend to be always on 24/7. To fix this, EEE establishes a so called ‘sleep mode’ function for the connection. EEE works like this: Once the router firmware realizes that there is no data to send, it orders the connection to switch into LPI or Low Power Idle mode. This LPI command tells the Ethernet transceivers (PHYs) to disable its transmitter, saving energy in the process.

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Now, LPI doesn’t mean the connection is completely turned off. While under LPI, the link still periodically refreshes itself to maintain connection integrity. Indeed even under LPI, the link can still receive new data. Once it has received new data, and there is new data to transmit back, the link switches to IDLE mode and goes back to normal operation shortly thereafter. The beauty of this approach is that it is backwards compatible with old devices that don’t use EEE. In those cases, it just functions as a normal ethernet link. But you don’t have to worry about it too much, as most PCs and ethernet devices support EEE nowadays.

But this technology is not without disadvantages. EEE may interfere with real time networking applications. If you are doing audio or video streaming, EEE can mess up with the synchronization, resulting in chopped audio or erratic video. Typically, this only happens in high bandwidth, low latency protocols. This is especially true if you have commercial audio/video equipment on the network that uses protocol such as Dante (Digital Audio Network Through Ethernet). In the end, this is a non issue for your average home use so don’t worry about it too much.

Buying a router or a switch with EEE will save you money. So if you’re looking for a new router/switch, be sure to check if it has EEE support. One thing to note is that EEE is just one subset of the Green Ethernet technology. In addition to EEE, Green Ethernet also adjusts the power sent to the cable based on its length among other things. While the savings might be minuscule, they add up over the course of the year. In fact, it is estimated that you can have from 45% to 80% power savings just from switching to routers/switches with Green Ethernet technology. So look for these technologies the next time you’re looking for a router.