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Cut that UC desktop power

Data center energy consumption is expected to constitute 3% of all electrical power consumption in the U.S. by 2010, according to the EPA. By conserving energy and adhering to best practices for power consumption control, CIOs can lower their companies' electric bills and move toward a green solution within the data center.

The growth of VoIP and the deployment of IP phones are increasing the power and air conditioning requirements in the LAN and telecom closets. The selection of LAN switches, UPS backup, what form of PoE delivery is installed, and Class 2 or 3 IP phones will all contribute to the energy bill. Gartner is predicting that power and cooling costs will be the second line item in the IT budget -- behind only staff salaries -- in 2009.

Did you know that greater than 1.5% of the electrical power consumed in the U.S. is for data center operation? This figure is expected to rise to 3% by 2010. These statistics were detailed by the Environmental Protection Agency (EPA) in its "Report to Congress on Server and Data Center Energy Efficiency" released in August 2007. The report does not include information about the power consumed in the telecom and LAN closets. When the closets are added to the bill, the power consumption by IT technology probably exceeds 2% of all energy consumed in the U.S. According to a Nemertes Research report, power and power scalability are the primary challenges for 63% of enterprises. How much of the power bill at your organization is for IT?

Who pays the energy bill is a matter that varies with the organization. I have not found an official survey of who pays for the energy consumed by IT. Many CIOs consider the costs of energy as a necessary part of doing business and have not purchased equipment that would significantly reduce their energy bill. Most of the attention has been focused on rack and floor space consumption. Packing more LAN switches per rack keeps the closet real-estate bill low, as floor space is not increased exponentially when new switches are added. The disadvantage of this approach is that the energy and air conditioning expense per closet square foot of space has risen significantly. A lesser-known fact is that for every 1W of IT equipment power consumed, 0.86W of air conditioning power is required to cool that equipment. The cost of the energy consumed in the closet is hidden in the general building budget, and few enterprises have any idea of what their energy use is truly costing.

Selection of an IP phone is usually determined based on features, functions and price -- not on energy consumption. There are two classes of IP phones on the market. The Class 2 IP phone consumes less than 7W of energy per phone, while the Class 3 phone can consume as much as 13W per phone. As the functionality increases, the power consumption increases also. Large color displays, broadband codecs and gigabit operation are three major causes of higher power consumption. Avoid the gigabit IP phones. Besides the cost of possible new cabling, the LAN switch ports are quite a bit more expensive. The power to drive the gigabit LAN port is 5W to 20W more than the 100 Mbps IP phone requires.

Paul Weismantel, director of product management for Avaya's Communications Appliances, spoke of Avaya's new gigabit Class 2 IP phones, which support color displays and broadband capability. These new IP phones use less than 7W (Class 2), when it is common to require Class 3 operations that consume more than 7W per phone.

The conservation mode of IP phones uses the IEEE Link Layer Discovery Protocol (LLDP) standard, which is similar to Cisco's CDP. These protocols operate from the LAN switch to the IP phone to determine the power class and deliver the appropriate power level. The conservation mode turns off the display when there is no phone activity. This further reduces the energy consumption. The LLDP and CDP features are available on several vendors' LAN switches.

Leaving the IP phones running for 24 hours, seven days a week, may be unnecessary. Scott Lucas of Extreme Networks mentioned a software feature in the LAN switches that allows specific PoE ports to be turned off when not needed. The Power Conservation Module Software can be programmed to turn off PoE ports for IP phones and WLAN access points when not needed at night, and on holidays and weekends. Some of the IP phones and WLAN access points can be left on for emergency calls and 911 access.

Assuming the IP phones are powered 12 hours per working day and turned off for nights, holidays and weekends, this feature could save 66% of power for each IP phone and WLAN access point turned off. Weismantel suggests that the enterprise use this feature carefully, powering up IP phones sequentially so that there is not a flood of IP phone registrations that could overload the DHCP, DNS and call servers.

If you are going to use them, softphones will help reduce power consumption, assuming that the desktop PC would be there anyway. The desktop is also a power consumer, however, expending about 80W. Sun Microsystems developed thin client technology as an alternative to the PC. The thin client consumes only 4W of energy and can provide all the features of a standalone PC when connected to the server.

The best practices for controlling power consumption are:

  • Avoid Class 3 IP phones.
  • Do not overbuy features that will consume more power.
  • Use LAN switches with LLDP or CDP.
  • Power down most IP phones overnight and on weekends.
  • Consider a thin client desktop.

About the author:
Gary Audin has more than 40 years of computer, communications and security experience. He has planned, designed, specified, implemented and operated data, LAN and telephone networks. These have included local area, national and international networks, as well as VoIP and IP convergent networks, in the U.S., Canada, Europe, Australia and Asia.

This was last published in April 2008

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