How and why to extend your network with power-line networking

By , ITworld |  Networking, power-line networking

Image credit: flickr/Micah Drushal

Back in 2001, when I first moved to Asheville, NC I had a 3,500 square foot house and my wife and I both had offices on different floors. Wi-Fi just wasn't cutting it, and while I used 10Base2, a.k.a. thinnet, to connect routers and switches between floors there was no way to make it look good. So I started experimenting with power-line networking, and I haven't looked back.

The reason for that is that power-line networking makes use of your electrical lines to give you a de facto wired network. It gives you the range of a wired network without any of the mess or the need to run cable behind the walls.

Another useful feature, which I've used in every place I've ever deployed, is that you can use it as the backbone for your Wi-Fi network. So, for example, in my current small office/home office (SOHO), I use it to connect my three Wi-Fi access points (APs) to my master switch. With this I have both direct wired access from my main office to my server room (doesn't everyone have a server room at home?) and strong Wi-Fi over my entire property.

How power-line networking works

At its heart, power-line networking is quite simple. It uses your existing electrical wiring as an Ethernet. The data signal rides on top of your 60 Hertz (Hz) AC power. The exact frequency power-line networking uses depends on which version of the technology you're using. Earlier versions used two to 28 MegaHertz (MHz). The IEEE 1901 standard extends this range optionally to 50MHz. This, in turn, enabled power-line networking to go as fast as 500 Megabits per second (Mbps). HomePlug AV2 uses frequencies from 30MHz to 86MHz to push throughput up to a theoretical 1 Gigabit per second (Gbps).

If you've ever worked as an electrician, you can see there's a potential problem here: Bad wiring or even power strips with filtering can absorb and weaken the power-line networking signal. That's exactly right. Older, poor quality wiring will reduce your data throughput. How much? The only way to know for sure is to try it and find out. Power strips can knock power-line network speeds down to almost nothing and should never be used with this networking technology.

Power-line history

Power-line networking got its start in 2000 when there was, of course, a standards war. The first technology, Intelogis' Passport, could only reach a speed of 350 Kilobits per second (Kbps). That was too slow for most practical purposes. So, Intellon's PowerPacket, which could go as fast as 14Mbps became the first wide-spread power-line networking standard in 2001.

The group, which gave PowerPacket its official blessing in 2001 as HomePlug 1.0, was the HomePlug Alliance. Today, it's still the organization that oversees home power-line networking, although the IEEE has also gotten involved in standardizing these networks.

Since HomePlug 1.0 appeared, this standard has kept getting improved and faster. Next up came HomePlug AV in 2005. It had a top speed of 200Mbps. That made it fast enough to run audio/video applications, hence the AV in its name. This is also the first version to support a real security standard: 128-bit Advanced Encryption Standard (AES).

For this reason, if your small business shares office space with other businesses, you should be using at least HomePlug AV. But most standalone homes and office buildings don't have to worry about signal leaking out to the public. Your AC transformer on the street will make sure your signal is blasted into noise before it leaves your property line.

To do its magic, HomePlug AV, and the technologies that came after it, all use orthogonal frequency-division multiplexing (OFDM) as its physical layer. It also includes support for Quality of Service (QoS), Universal Plug and Play (UPnP), and all the usual TCP/IP Ethernet protocols. In short, it provides a full, conventional network stack. This standard was also the first to be incorporated into the IEEE family with the IEEE 1901 specification.

At about the same time, Powerline AV was introduced. This technology, while slower (it can only reach 100Mbps) can work transparently with 10/100 Ethernet standards. What that means is you can integrate it with older Ethernet setups. Since its introduction, it has been superseded first by Powerline AV 200, which can reach 200Mbps, and by Powerline AV 500. The latter can run at either 100Mbps, on older Ethernet infrastructures, or at 500Mbps on Gigabit Ethernet. This last technology has been incorporated into IEEE 1901.

In 2012, the HomePlug Alliance introduced HomePlug AV2. This technology can reach, or so they say, 1 Gbps speeds. It really started to roll out in 2013 and it's only now going mainstream.

One reason I mention all these technologies is that I've seen all of them still for sale -- yes even 14Mbps HomePlug 1.0 devices. I've also seen many offices that have adopted power-line networking using a mix of different adapters. Fortunately, except for HomePlug 1.0, all these standards tend to be backwards compatible. So, for example, you can still use your HomePlug AV adapters with HomePlug AV2. You won't get the newer standard's speed, of course, but it can work.

You should also know that all these speeds are lab speeds. In my offices, I usually see 50% to 66% of the advertised speeds. That's about on par with Wi-Fi's quoted and real-world speeds.

Power-line networking pros and cons in the real world

Why should you use power-line? Well, first and foremost, it's easy. There's usually no software setup; you just plug one unit into the wall socket, plug its Ethernet cable into your router or switch, plug the other adapter in near your remote PC, another router, or a Wi-Fi AP (access point), hook them up together, and ta-da, instant network.

Power-line also has far less latency than Wi-Fi typically does. That can be a real advantage if you play games on your network.

As I mentioned earlier, I often use power-line networking to hook up Wi-Fi APs and routers. There are two ways to do this. One is to simply use a power-line adapter that includes a Wi-FI AP or a router with Ethernet ports. For Wi-Fi, look to adapters such as NetGear's XAVNB2001, which includes a 802.11n AP and 200Mbps HomePlug AV200. For adapters that come with multiple Ethernet ports seek out the D-Link DHP-540 PowerLine AV 500 4-Port Gigabit Switch or the ZyXEL Powerline AV 500Mbps 4 Port Gigabit Switch Wall-plug Adapter with PLA4205 Powerline AV 500Mbps (PLA4225KIT) Both come with 4Gbps ports and support Powerline AV 500 for speeds of up to 500Mbps.

On the downside, besides being affected by your electrical wiring's quality, power-line networking can be messed up by some home appliances. In particular, electrical devices with a motor, such as vacuum cleaners and dryers, can slow down your network connection while they're in use.

You should also be careful of mixing and matching power-line equipment across vendors. In theory, one device of the same standard should work with another without any worries. In practice, it's a different story. In my experience the problem usually comes down to how each vendor implements security. I've usually been able to get them to work together by getting them on the same security page, but it's often not easy due to inadequate documentation.

That's it for the bad side of power-line networking. It really does just work and it extends your network with little fuss or muss.

Some power-line adapters to try

I've used all of these adapters either in my own SOHO or deployed them in other offices. There may better ones out there, but I know these work well.

ZyXel PLA4205

With Gigabit Ethernet and Powerline AV 500, the ZyXel PLA4205 is the fastest Powerline device out there, but it's also very bulky.

Image credit: XyXel

When you start shopping for power-line adapters, you'll find that in your typical electronics store they come as pairs. That makes sense. You must have two to do anything with them. But, after you get the first pair, and you want to extend your network you will probably need to contact the vendor to order single units.

The ZyXel PLA4205 works well and supports both Gigabit Ethernet and Power-line AV 500. It's the fastest power-line device available on the market today that I've used. It, however, does not actually hit 500Mbps. The best I've seen out of this pair is 226Mbps. That's still more than fast enough for most practical purposes.

NetGear's Powerline 500Mbps 2-Port Adapter

The NetGear's Powerline 500Mbps 2-Port Adapter is almost as fast as the ZyXel and it includes a power pass through socket outlet. If you're short on outlets, this can be a life-saver.

Image credit: NetGear

At a street price of $50 for one or $80 for the pair, it's also very affordable. The one drawback is it's also very big for this kind of device, making it tough to squeeze into tight places.

Almost as fast, is NetGear's Powerline 500Mbps 2-Port Adapter - Starter Kit (XAVB5602). Like the ZyXel, it's too darn big and it's not as fast as it should be. I've seen only 172Mbps out of it.

This NetGear device is also more expensive than the ZyXel. It runs for about $199 for a pair. I still like it for one good feature: It includes a pass-through socket so you don't lose a power outlet like you do with most Power-line network gear.

ActionTec 500 AV

Far from the fastest Powerline AV 500 devices, the ActionTec 500 AV Powerline Network Adapter makes up for it by being both small and affordable.

Image credit: ActionTec

Finally, I like the ActionTec 500 AV Powerline Network Adapter - Single Port for tight places when you're on a budget. It only supports Fast Ethernet (100Mbps) on the Ethernet half so even though the power-line side supports Powerline AV 500 you can't even in theory get more than 100Mbps out of it. That said, it does get the most it can out of that 100Mbps, I've seen speeds of up to 73Mbps from these units.

Unlike the others, it's also compact and will fit into most cramped behind the desk spaces and at $40 per pair, you're not going to get more network bang for the buck. As long as you're not editing photographs or video over it, I think you'll find it more than fast enough for most of your office needs.

Whatever device you get, power-line networking will make your networking life much easier. I know it has mine! Enjoy!

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