So what's the downside?
Power-line networking sounds like magic so far, doesn't it? Well, it's not exactly. HomePlug has its limitations, frustrations, and weird quirks--but arguably fewer than you'd expect for a technology that works in such an unfriendly environment as your power grid.
The numbers game
You can hook up a maximum of 16 computers to a current power-line network. For a home network, that's not a serious limitation. But there's another less well-known limitation to the first wave of Intellon chipset-based HomePlug adapters (which covers nearly all such devices currently on the market). If you're not installing Windows drivers for your HomePlug adapters, you're limited to three driverless devices per network. So you can't, say, hook up two Macs, a router, and an Xbox on the same power-line network. However, with the drivers installed, you can install five each of the Ethernet and USB-based adapters, then throw in a router and two Macs. And you can wire three extra devices to the router to expand the network using traditional Ethernet.
Stretching the limit
There is a functional limit of 1,000 feet for HomePlug networks, but if the west wing of your mansion is 900 feet away from your broadband access point, you'll be out of luck. The 1,000-feet limit refers to the length of the wires, not the physical air space, and wires tend to take the long way around wall cavities.
Macs can apply...but can't control
Macs with Ethernet network cards can take full advantage of power-line networks, but they can't program new passwords into the adapters. The off-the-shelf utility that currently ships with all HomePlug adapters is a Windows-based program. You'll need access to at least one Ethernet or USB-enabled Windows PC to reset your network's passwords. And because of a limitation with the first wave of HomePlug chipsets, you can't attach more than three Macs to a power-line network; to attach more requires drivers, and so far, Mac drivers aren't available.
Power strips strip power-line networks
HomePlug adapters need their own power socket. Don't plug a power-line adapter into an extension cord, a line splitter, or a power strip; these can contain surge protection that strips out the data signals and brings down your power-line network. And remember that some offices and home offices have surge protection built in at the socket, so these too will render HomePlug adapters useless.
Power struggles
Science class painted a rosy picture of electricity in the form of regular sine waves. But these perfect curves of 110-volt AC seldom grace the wires of real homes. For one thing, the energy coming off the power grid into your home is rarely clean; it suffers spikes (sudden rises in energy), surges (prolonged overvoltages), and brownouts (prolonged undervoltages). And once electricity is in your home, "noisy" appliances such as vacuum cleaners, air conditioners, and hair dryers dirty up that perfect wave pattern even more.
This means that power-line networks run over an unpredictable medium. When our test machines suddenly lost Internet access, for instance, the lack of network diagnostic tools for power-line networks really hurt. Apart from Windows' own IP Configuration (winipcfg and ipconfig) and ping commands, there are few tools and fewer techniques to figure out what's happening. Thankfully, during the course of our evaluation, the tech-support lines for the major vendors of HomePlug devices became better at troubleshooting such issues.
This isn't to say that HomePlug networking is riddled with troubles. Over several months of evaluation in a 70-year-old home in the full heat and humidity of summer, when wall air conditioning units kick in and brownouts are common, we encountered only one unexplained network dropout. We easily fixed the problem with the old trick of unplugging the adapters and plugging them back in again after a few seconds.
Just show me the products
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