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How Power over Ethernet can help you power your network and beyond

Unified access layer for wired and wireless LAN with HP - Part 8


By Rebecca Humphress, HP Networking Global Product Marketing & interviews with Leonard Knapp, Tom Kinahan, and Parvez Syed Mohammed – HP Networking Global Product Line Managers


I was recently given the opportunity to interview three HP Networking Global Product Line Managers about Power over Ethernet, or PoE.  Although PoE is nothing new for switches, I wanted to hear from them on why PoE is still such a hot topic. Here’s how our discussion went. Please join the conversation too.


Rebecca: Hi guys.  Thanks for joining me today.  Power over Ethernet was first standardized from IEEE in 2003 and was first implemented on HP switches soon after.  Now that it’s a prevalent standard in the industry, let’s talk about some of the key benefits it provides.


Leonard: PoE provides convenience, cost savings, and in some cases, solutions that would be very difficult to provide any other way.  What I mean by convenience is for example that clients can be placed wherever they are needed without having to have power close by – just the wired Ethernet connection.  The most obvious client type that can take advantage of this is the Wireless Access Point (AP).  The AP can be situated for best radio signal characteristics, or hiding it in the overhead plenum without concern for pulling power to that spot.  Also allows easy moving if need be.  Security cameras are another example where power convenience is of upmost importance.  Another key benefit is cost savings.  Getting power to areas that are not typically served by power can greatly reduce installation cost.  Power circuits require electricians and breaker boxes.  Providing power right in the Ethernet cable avoids all of this.  Moving the client if necessary is also much easier.  Finally, PoE enables solutions that are not available otherwise.  For example, building infrastructure, such as network controlled security door locks or the above-mentioned security camera, would be difficult without PoE power.  Also, computers that can be used in kiosks, or other places that need location flexibility, and that run entirely off of standard PoE power, such as the HP t410 All-in-One Smart Zero Client, are starting to appear.  Many of these solutions wouldn’t supply the flexibility of location without PoE.


Rebecca: Wow, Leonard, great stuff!  So one thing that customers are always concerned about is the amount of power required for their IT resources such as switches.  Can PoE help me increase my energy efficiency?


Leonard: There are a number of ways that energy efficiency can be provided with PoE, but those have to be balanced against resistive loss in the Ethernet cable itself.  For instance, the power supplies in PoE capable switches are usually more efficient as their loads increase up to about 50% load in the higher efficiency supplies.  Aggregating the power needs of many smaller power supplies by using a few larger power supplies can help increase overall power efficiency.  Secondly, power applied to PoE clients can be controlled by the switch.  For example, it is possible to turn off power to individual clients via the switch.  Power managed environments could turn off clients when not needed, such as at night, or on weekends and holidays.  And there is no ‘vampire power’ loss – loss from plugged in supplies for clients that are not being used with PoE power.  Finally, just to balance against the efficiency savings stated above, power transmission over the 28 gauge twisted-pair wire does create increasing resistive loss as the wattage delivered to the client increases and cable runs get longer.  The maximum power allowed for a PoE client is 15.4W (PoE+ 34.2W), but the guaranteed delivered power is 12.95W PoE+ 25/5W) to account for maximum cable loss over 100m of cable.  Although there are power efficiency benefits to PoE, customers usually purchase switches with PoE in order for convenience, power control and installation simplicity.


Rebecca: OK, so now we know that PoE brings convenience, power control and installation simplicity.  Talk to me about the applications that PoE enables.


Tom: The applications I’ve seen over the years are Wireless access points, cameras, IP Phones that are the obvious solutions.  Clocks, PA system speakers, thin clients, small displays in a store, using a thin client, an entire Point of sale system without power wiring are some of the other more unique applications that have been enabled through PoE.  The importance of PoE for HP Wired and Wireless Access is that PoE-enabled switches allow for powering of Wireless APs at the edge of the network. 


Rebecca: Got it – from simply being able to power key business devices like IP phones to unique solutions such as clocks, PoE has the ability to power a lot of solutions for customers. Any deployment advice?


Parvez:  Carefully plan the power needs before purchasing and configuring your PoE switch.  Many HP switches have a pool of PoE power across all ports on a switch.  Depending on the power pull from the end device, the switch might be able to provide power out of all ports giving availability to many devices at one.  Some common devices and their average power requirements are: IP Phones at ~7W, Wireless APs at ~15W, still cameras at ~15W, and pan-tilt-zoom cameras at ~25W.  Also, don’t underestimate the power needed at the switch.  Heavily loaded switches may need a number of independent 20A @110V (10A @ 220V) circuits available where the switch is installed.  In a data center or large wiring-closet that level of power may be available, but smaller closets may need additional power circuits pulled to the closet to provide this level of power.


Rebecca: Thanks!  This has been very educational!  I now know what to look for and how to prepare for deploying PoE.  


We offer a comprehensive portfolio of campus access technologies that provide Power over Ethernet.  PoE enables the HP Wired & Wireless Unified Access solution by providing power from switches to wireless APs at the edge of the network.  HP delivers unified wired and wireless LAN access layer with single network management, monitoring and security application providing single-pane-of-glass management. 


How do you deploy PoE and  what are your PoE needs?  We’d love to hear your feedback. 


>> Find more information about HP’s Unified Wired and Wireless Access and catch the most recent blog in our series focused on sFlow.



Follow our blog series: Unified access layer for wired and wireless LAN with HP


HP unified access solution helps you address your security, scalability, management and WLAN design challenges. Now through the end of the year, we’ll be discussing the hot topics, challenges, benefits, technologies and innovations related to unified access. Join us!


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