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Ron Pacchiano, Practically Networked 2nd July 2004
An extract from a larger Q&A session, this article explains the difference between the two easily confused technologies.
Q: I was hoping you could settle a disagreement between me and some of my co-workers. I was talking with a couple of them about a home networking problem I was having when one of them suggested that I look into possibly setting up a Power over Ethernet network. I had never heard of this before and thought that he had actually meant to say a Powerline network. His response was, "They are the same thing." I disagreed.
So we brought our disagreement to some of the other technicians for their input. Most of them hadn't even heard of either one, and a few of them agreed with my associate that the two are in fact the same. I still insist that they are different and was hoping that you could set the record straight. Are they the same? If not, then what is Power over Ethernet? I have $60 bucks riding on this, so please don't let me down.
A: I have to tell you, there's almost nothing I enjoy more than taking money off of my co-workers when they tell me that I'm wrong in my interpretation of a technical issue. Fortunately, today you get to share in that feeling.
You are indeed correct in your assertion that Powerline networks are in fact different from Power over Ethernet (PoE). Powerline, or HomePlug, networks use the electrical cabling already running throughout your house to carry data between your systems. They have a throughput rating of 14Mbps and support a 56-bit data encryption standard (DES) for security and privacy. They don't use any device drivers, which makes them easy to install, and many Powerline solutions can be purchased for about $100.
Power over Ethernet, also known as IEEE 802.3af, is a technology standard designed for wired Ethernet local area networks (LANs) that allows the electrical current necessary for the operation of a network device to be carried by the Ethernet cables rather than through separate power cords. The most significant benefit of PoE is that it minimizes the number of wires that must be strung in order to install the network. This results in lower cost, less downtime, easier maintenance, and greater installation flexibility than you have with traditional wiring.
For PoE to work, the electrical current must go into the data cable at the power supply end (usually referred to as a "power hub") and come out at the device end in such a way that the current is kept separate from the data signal so that neither interferes with the other. The current enters the cable by means of a component called an injector. If the device at the other end of the cable is PoE-compatible, then that device will function properly without modification. If the device is not PoE-compatible, then a component called a picker or tap must be installed to remove the current from the cable. This "picked-off" current is then routed to the power jack.
To minimize the possibility of damage to equipment in the event of a malfunction, the more sophisticated PoE systems employ a kind of surge protection. This feature shuts off the power supply if an excessive current or a short circuit is detected.
Even with the recent standardization of PoE as IEEE 802.3af, it is still an evolving technology with many hurdles to overcome. However, it has the potential to create a whole new world of smart networked appliances, such as Internet-enabled Refrigerators, because of its unique ability to provide power as well as data over nothing more than an existing Ethernet cable.
Enjoy your new found cash and try not to gloat too much when you take it.