What does the new Power over Ethernet standard mean for IT pros?

The IEEE802.3at Power over Ethernet (PoE) standard was ratified earlier this month. For the uninitiated, what does the migration to PoE entail? Blogger Paul Mah takes a look at some of the considerations.

The ratification of the IEEE802.3at standard this month means that compliant Power over Ethernet (PoE) devices can now transmit up to 25W over Ethernet cabling to network appliances or equipment, which is a substantial increase from the 15.4W specified under the earlier IEEE 802.3af PoE standard.

Whether much new hardware will spring forth to take advantage of the additional power remains to be seen, although more powerful thin clients and wireless network access points come to mind. No matter what, it would be reasonable to expect adoption of PoE to gain momentum over time.

With this in mind, what does deploying Power over Ethernet mean for the IT professional?

Migrating to PoE

The obvious disadvantage of bringing PoE to an organization not already on the bandwagon is the simple fact that existing switches are effectively redundant. While the cleanest solution might be to deploy new PoE-compliant equipment across the board, the feasibility depends largely on the actual strategy to make use of PoE. Ultimately, the probability of convincing management of such a broad change would likely be low.

An alternative would be to consider the use of a midspan. What a midspan essentially does is sit between an existing non-PoE switch and the connected network device for the specific purpose of injecting power into the cable. This might be the logical solution for most companies, seeing that it allows a gradual phasing in of PoE. In addition, organizations do not pay for additional ports where the connected equipment does not make use of PoE.

Is it dangerous to transmit so much power over Ethernet?

I looked around and found a recent article in which TMC.net interviewed Amit Gattani, Director of Marketing for Akros Silicon. According to Akros Silicon's Web site, the company was actively involved with drafting the new 802.3at standard.

Gattani noted that 13W solutions will require only Cat 5 cable while 30W solutions will need Cat 5e and above. The reason, he says, is that "Cat 5e and above have lower resistance drops so the heating issue is less." Pertaining to concerns about the dangers of overheating, Gattani told TMC.net, "The 30W power limitation is actually put in place for a high degree of safety margin from the cable bundle heating up."

So while the probability of PoE-powered Ethernet cables heating up is there, it should not pose a problem in most instances.

Impact on cooling and energy consumption

Will the use of PoE change the dynamics of the data center or server room in terms of energy consumption? I had the opportunity to interview the top executives of Chloride Powers on their stopover in Singapore last week and posed this question to them.

Etienne Gurou, Vice President of Chloride South East Asia, took the question. He pointed out that ultimately, the energy consumption remains similar -- less some power loss on the wire of course -- regardless of how it gets there. As such, what needs to be attended to would be issues pertaining to the ventilation and cooling of the slightly warmer cables or the powered hardware rather than any actual re-architecture of the datacenter.


When all is said and done, the ratification of the more advanced IEEE802.3at standard is hardly earth shattering. However, the increased maximum power can only mean a wider range of applications that will eventually be possible and, ultimately, the increased deployment of PoE on the whole.

Have you deployed PoE in your organization? Feel free to share your experiences with it below.