PoE is Ready to Deliver
New standards boost power to 30 and 60 watts
- By Sani Ronen
- Jun 01, 2010
With the ratification of the IEEE802.3at standard in September 2009, Power over Ethernet is ready to deliver 30 to 60 watts of safe power over a single Ethernet cable to a broad range of security products, including access control systems, PTZ cameras, outdoor cameras and even full outdoor solutions that include a heater.
The Move to High Power
PoE technology, which enables networked devices to be powered over the same Ethernet cabling infrastructure as data, provides important benefits in security applications. It eliminates costly AC outlet installation and allows network cameras to be deployed in difficult-to-reach locations. PoE also simplifies the job of resetting, repositioning equipment and delivering emergency backup power. Finally, PoE’s advanced line terminal detection ensures that a faulty camera or access control terminal can be detected and shut down, preventing damage to expensive switches and patch panels.
Now, PoE is poised to deliver even greater benefits with the move to high-power standards. The first PoE standard was ratified in 2003, defining the detection and protection parameters of PoE systems delivering up to 15.4 watts. The security market adopted the PoE standard quickly due to the major benefits it offered for security device installation and maintenance.
In recent years, PoE has become a common feature of network IP cameras, which generally include it as a powering option in addition to the traditional DC input barrel. Some innovative vendors have chosen to fully adopt PoE technology and have offered IP cameras that are exclusively powered by PoE. These models are becoming increasingly popular and widely adopted, and it is expected that more vendors will add PoE IP cameras to their portfolio.
Challenges and Opportunities
Before PoE can really take off in security applications, it must be able to accommodate powered devices that require 30 watts of power or more. The original, standard-power IEEE802.3af standard specified that a PoE switch or midspan will deliver up to 15.4 watts. It also defined consumption of up to 12.95 watts by the powered device, which may be installed up to 100 meters from the switch. This power limitation has prevented high-power devices, such as PTZ cameras and advanced access control solutions, to be powered via an industry-standard PoE solution.
The new IEEE802.3at standard roughly doubles what power sourcing equipment can deliver and what powered devices can receive -- to 30 and 25.5 watts, respectively. It also increases PSE output voltage to between 50 and 57 volts and boosts maximum ongoing current to 600 mA.
The most important benefit of the new standard is that it relies on the field-proven detection and protection concepts of the existing 802.3af standard, thus enabling fast and safe adoption of the new standard by security equipment vendors.
The First Power Step: 30 Watt PoE
As mentioned above, the new PoE standard defines delivery of 30 watts over two pairs of Ethernet cable, guaranteeing delivery of 25.5 watts across distances up to 100 meters. Many PTZ cameras use an internal engine to change the camera position, and these will now be able to receive the full power they require from PoE (typically 12 to 20 watts). Most PTZ cameras are already PoE-ready and can be powered via 802.3at sources. The transition to high-power PoE will be easy.
The access control market had adopted PoE a bit more slowly, mainly due to the similarly slow adoption of the underlying Ethernet technology as a replacement for older serial protocols used by access control systems. The new 30 watts option will significantly accelerate the deployment of access control devices that need more power for the controller, the reader and even the door lock.
The Second Power Step: 60 watt PoE
One of the most exciting and revolutionary opportunities with the latest high-power standards is the option to deploy PoE functionality over all four pairs of the Ethernet cable. This option opens the door for safely delivering 60 watts of DC power over a single Ethernet cable, using current levels of 600 mA rather than the 1.2 amp level of two-pair 60 watt midspans.
It is important to repeat the word “safe” here. Be wary of solutions that promise greater than 60 watt/port. Anything above 60 watt/port can pose standards-compliance problems, and anything over 100 watt/port poses significant safety risks. But with the latest four-pair 802.3at solutions, security professionals can go well beyond the 25.5 watt of two-pair solutions to achieve PD power consumption of 51 watts, using fully compliant, industry-standard 60 watts PoE technology at the source. And because they’re backed by IEEE standards, today’s 802.3at-compliant midspans incorporate all necessary PD PoE compliance detection features for safe powering, as well as safe PD disconnection in overload, short circuit or under-load conditions.
A major advantage of midspans becomes more apparent with the higher power standards: reliability. The mean time between failures of PoE switches is considerably lower, when compared with their non-PoE counterparts. This “TV-with-built-in-VCR” effect is due to the concentration of high-power dissipation from the PoE section and the highly sensitive data section into a single box. For example, Cisco’s 3750X-48T (non-PoE) has 171,846 hours of MTBF, while the 3750X-48P (its PoE counterpart) has an MTBF of only 139,913 hours, an almost 20 percent smaller lifetime. And what’s worse, once there is an issue, one pays for both data and power again, instead of dealing only with the section where the issue exists.
The primary applications for 51 watts PoE power delivery are full systems that include an IP camera with additional power-consuming accessories such as a heater. In the access control market, a full system that includes a controller, a reader and a few door locks can easily consume 45 watts of power.
PoE Deployment
There are two ways to deploy the latest high-power PoE technol¬ogy in security applications: by upgrading the switch or by adding midspans to the existing switch infrastructure.
Typically, midspans offer the most flexible, scalable, manageable and energy-efficient solution, especially for first-time PoE deployment. Unless the existing data network infrastructure has inadequate features, capacity or performance, which would make a switch upgrade desirable, midspans are the best PoE deployment choice, since they require no changes to the existing switch or cabling, and are generally compatible with any Ethernet switch.
Also, midspans decouple the power and data infrastructures to optimize deployment flexibility and scalability. With midspans, security professionals can incrementally add PoE ports only as needed. This contrasts with the installation of a new switch, for which best practices prescribe PoE deployment on as many ports as possible to support future growth. Using midspans, flexibility can be further ensured through the inclusion of a gigabit interface so the midspan can more easily support high-power PTZ cameras and thin clients. These and other devices, such as gigabit video phones, WiMAX transmitters and 802.11n access points, also require two-event classification support per IEEE 802.3at specifications.
To maximize scalability, the inclusion of an interlocking feature enables the power infrastructure to be expanded in one-port midspan increments as new PDs are added. Other options that enhance flexibility include the ability to use DC inputs with external power supplies for incremental power capacity or redun¬dancy and flexible powering from AC, DC or another midspan. Interconnected midspans also can back each other up in this kind of installation.
Maintenance Considerations
Once deployed, a midspan-based PoE infrastructure also is easier to manage and maintain than other alternatives. Midspans deliver remote power-management capabilities that support both IPv4 and IPv4/6 addressing, which allows simple and efficient monitoring and control of powered devices. This increases in importance with network size and complexity. Remote power management also enables unit scheduling, UPS power monitoring and Web-based monitoring. Malfunctioning remote devices can be reset, eliminating an expensive service call.
Enterprise-grade midspans also enable centralized control of multi-site or multi-building installations, with support for immediate alert (e.g., E911) and response if IP phone status changes. When the midspan is integrated with a UPS system, the remote power-off/power-on capability also enables low-priority ports to be disconnected during power failures. Remote power manage¬ment must be performed in a secure fashion, so SNMPv3 management is recommended to prevent malefic agents from interfering with network operations.
Finally, midspan-based PoE solutions also significantly improve energy efficiency, which is an important consideration for any cost-savvy customer. The remote-management features alone provide an easy way to power selected ports up or down during the day, which can reduce power consumption by 70 percent. Each device’s power consumption can be measured, and its average power consumption can be actively reduced.
Consider a typical 1U 24-port midspan, for which there will be 24x15.4 watts, or 370 watts, of power to manage. The real-time power needs of the various PDs on the network might only be just over half that requirement.
The latest enterprise-grade midspans owe much of their efficiency to their distributed power architecture. In another example, consider a 48-port switch with 800 watts of full IEEE802.3af power per port, which might waste 80 watts of quiescent power since as few as 20 ports are used at any given time. In high-power IEEE802.3at applications, it is rare for any single port to require full power. Therefore, today’s enterprise-grade PoE midspans augment smaller, more economical internal default power supplies with external power supplies for incremental additional power, or for redundancy.
This distributed architecture improves system efficiency and reduces cooling costs since smaller supplies require smaller and/or lower-speed fans. As mentioned earlier, this approach also enables midspans to back each other up, with additional power sup¬ply serving the highest-priority system ports.
Power efficiency can be further improved through good PoE system deployment practices. PoE is already the greatest heat generator in most switching closets, and cooling challenges are considered the biggest potential roadblock for widespread high-power PoE deployment. Midspans solve this problem because they diminish heat concentration. By delivering only the power necessary, they are significantly more green than PoE switches. Midspans can be used alone or combined with PoE switches to power both low- and high-power devices for the most energy-efficient solution.
For even better power efficiency, the four-pair powering approach mentioned earlier also can be used to power two-pair devices with 30 watts of power, while dissipating up to half the power and consuming almost 15 percent less energy than conventional two-pair solutions. This translates into savings of approximately $25 per year per powered device, assuming energy costs of $0.10 per kilowatt hour.
Protecting Outdoor Gear
Another key consideration for security professionals is whether their powering solution can support the environmental requirements of PDs, such as outdoor IP cameras. Until recently, PoE technology could only be deployed safely with a costly surge-protection unit installed alongside it, to prevent direct or nearby lightning strikes from damaging or destroying both the PDs and their network switch. Surge and lightning protection units can
cost up to $400.
Because of this expense, a high percentage of outdoor PoE installations, especially in the enterprise, do not implement surge protection. Unfortunately, nearby lightning strikes are much more common than most people think, and strikes as far as a mile away can induce a voltage level that can damage outdoor devices. Without lightning protection, surges also can move quickly along the Ethernet cable to damage expensive indoor network switches.
By incorporating surge protection directly into the midspan unit, it is possible to reduce surge-protection costs by as much as 80 percent compared to using stand-alone surge-protection equipment. Midspans with lightning protection should be tested successfully to the GR-1089 lightning standard for surges up to 2,500 volts/500 amps.
Planning for More Power
There are already many PTZ cameras, access control systems and other PDs that consume up to 30 watts, and a growing array of other systems need 45 watts and higher, including IP cameras that feature a heater or access control systems that include a controller, a reader and multiple door locks. The main concern is the availability of the PSE solution. The latest generation of high-power PoE midspans solves the power-sourcing challenge while offering a superior alternative to upgrading the entire switch to PoE, and some systems also feature capabilities such as lightning protection, which is critical for security gear that is deployed outdoors.
Today’s midspans also improve flexibility and scalability, management and maintenance, and overall system energy efficiency. Security professionals who plan ahead and choose midspans with smart, remote power-management functionality can significantly improve overall system energy efficiency. Additionally, if they choose midspans that are capable of industry-standard powering on spare pairs, they can take advantage of the industry-standard high-power delivery and further improved energy efficiency of IEEE802.3at-compatible four-pair powering.
This article originally appeared in the June 2010 issue of Network-Centric Security.