It is always dangerous to speculate, particularly in this industry, which sometimes seems to be more founded on speculation than practical reality. Consider, for example, Power over Ethernet (PoE)—essentially offering a way of delivering power through an Ethernet cable. Today, there are a multitude of different devices that can be attached to a network—WiFi repeaters, video cameras and so on—whose location may not be near a power socket. It makes sense, therefore, that the wire used to connect the device to the network is also the wire supplying the power.

Where PoE has really come into its own is with VoIP phones—telephone handsets that use a network-based infrastructure rather than a traditional PBX. Voice over IP handsets are exactly the kind of devices that can benefit from power over the net, just as old-fashioned analogue handsets are powered by the PBX. The alternative is to have a transformer next to every phone, which occupies a socket and is one more thing to go wrong.

The downside of PoE is, of course, in the "P". I've written before about how hard it is for hardware vendors in general, and networking vendors in particular, to claim any sort of green credentials for their equipment. The fact that PoE is delivering power, makes it a bit of an anathema to green—particularly as the latest iteration of the standard enables more power, not less, to be delivered over the Ethernet ports. According to the marketing, such power increases are required to support the increasing complexity of VoIP handsets. Colour screens, bigger processors, more memory—all of these things will take their toll and become more of a draw on the corporate power supply. That's all very well, but it's not very green, is it?

On the surface, then, Power over Ethernet can hardly be held up as a poster child for green IT. That's not necessarily the end of the story, however. Let's consider some of the plans and likely developments in the PoE space: not least that it may well become built into switches by default, rather than as an exception. From a systems architecture (and indeed, from a manufacturing) perspective, there is little difference between powered and unpowered Ethernet ports. One of the larger network vendors told me that the chances were most of their switches would build in PoE to all ports, at some point in the future.

In principle, that's still not very green—but there's more. There are no concrete examples yet, but vendors are also talking about incorporating power regulation directly into network switches; put simply, enabling the switch to regulate supply according to demand. It is not beyond the realms of possibility to imagine the automatic power-down of devices outside certain hours, or indeed, when no data signals were detected (pretty obvious for IP phones, for example). To take this one step further, it is within the realms of possibility to produce handsets that require only a trickle current when in standby mode—and which could signal their requirements to the switch.

Taking such thoughts to their logical extreme, would it be possible to furnish an entire building with a highly regulated, low-voltage, direct current power circuit based on flood wiring (that is, the networking sockets on the wall)? In principle yes—though indeed, there are a number of hoops to be jumped through first. Not only are there the technological hurdles such as the ones above, but also some basic truths, such as the fact that most network wall sockets are not actually enabled: they may connect to a patch panel somewhere, but this will not necessarily be connected to a switch.

All the same, while it may not yet be possible, there is certainly potential. Such a circuit might, for example, be able to replace the currently obligatory raft of telephone and PDA chargers that litter our offices - indeed, I discussed such a thing with one of the senior guys at network wiring specialist CommScope (who brought up the "not-all-ports-are-wired" issue—thanks Ian). Perhaps it might never happen, but it is often only in hindsight that we understand how technologies are to be used: in this case there has already been a precedent set with the charging potential of USB. Why not the same with the network? Such an infrastructure would be able to support a broader range of devices, far more straightforwardly than relying on the mains: as my colleague Tony Lock has pointed out, consider the efforts of the thin client vendors such as Wyse, who are bringing out devices with power requirements small enough to be powered by PoE alone.

Indeed, it can be dangerous to speculate. But equally, just as many technologies also have a downside, so there may be some upsides of PoE we are yet to experience. Just perhaps, and even taking into account the cost of manufacture, Power over Ethernet might just offer an opportunity for networking to demonstrate its green credentials at last.