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By | Bob Tarzey 18th July 2005 10:44

Time to turn on to power over Ethernet?

Old idea, new energy

Quocirca’s changing channels With the uptake of IP telephony continuing apace and the proliferation of IP devices in general, has the time finally arrived for an old concept – power over Ethernet (PoE)? For certain deployments of IP based technology, PoE is not only cost effective but arguably essential.

IP enabled devices like telephones and surveillance cameras that are always on need power, and power means cables. So although most IP devices have the potential to attach to a wireless data network, they can never be truly wireless because of the need for power.

But for such devices the power requirements are low. Low enough that just like traditional telephones, both the power and service can be provided by the same cable. This is the concept behind PoE – delivery of low voltage power to a device over a standard Ethernet data cable.

This is not a new concept, the idea has been around for years, but take up has been limited. One reason for this has been the lack of standards, but this has changed. The 802.3af standard, agreed a few years ago, is now being widely adopted. Cisco, the leading supplier of data networking products and a major supplier of IP devices, switched from its own proprietary way of doing things soon after the standard was introduced, and many other vendors have now followed suit. This allows for interoperability between different products, allowing resellers to put together proposals based on components from a range of suppliers.

Another reason for the slow uptake has been lack of applications, but this too is changing fast, largely driven by the take up of IP telephony. On the surface this would seem an unlikely driver as most IP phones will be on desktops and desktops have power – if the phone needs power, just plug it in.

But there are two reasons that make PoE attractive for IP telephony. First not all phones are on desktops, they are also in meeting rooms, corridors, store rooms etc. Sometimes they are in places where a convenient power socket may not be available. With PoE this is not a big problem; unlike high voltage mains supply, IT staff can install Ethernet cable.

However, there is another more compelling reason. Telephones need to work in an emergency including when there is a power failure. Traditional telephones do, but IP phones will only do so if there is an uninterrupted power supply (UPS). The only practical way of guaranteeing power supply to a large number of IP phones is PoE.

Enabling PoE requires network switches or routers that have been built to handle both data and power supply and these can be powered by a UPS. The cost of upgrading or replacing existing switches and routers can be high making the introduction of PoE prohibitive and driving up the cost of IP telephony implementations. But even if the cost of upgrade or replacement cannot be justified there is an alternative.

So called ‘midspan’ devices from vendors like PowerDsine are about one tenth the cost of a traditional switch and can draw power from the mains and data from a switch or router and feed into a single Ethernet cable. Of course, they too need a UPS if power is to be maintained during an outage.

The most compelling reason for enabling PoE is IP telephony, but once it is in place other applications become more practical to implement. IP surveillance cameras are pretty cheap now and capable of being powered by Ethernet. Wireless access points themselves can be powered by Ethernet; they have to have a data connection and their placement is more flexible if it is also their source of power.

Standardisation and new technology have made PoE a more practical proposition, but it will be business take up of IP based applications that will justify the cost. Once enabling PoE has been put in place for an initial project other opportunities open up.

© Quocirca

Bob Tarzey is a service director at Quocirca focussed on the route to market for IT products and services in Europe. Quocirca is a UK-based perceptional research and analysis firm with a focus on the European market.

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