Tag Archive for POE

| November 17, 2015
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Sun Setting on Cat 5e

Sun Setting on Cat 5eThe sun is setting on the Cat 5e cabling standard. The long-standing standard defined how most commercial spaces around the world were cabled for nearly 20 years. Starting in 2017 Cat 5e will be considered obsolete for new installations following a decision by the ISO/IEC cabling standards body.

recommendation for Category 6AIn a recent blog post at CommScope (COMM), the ISO cabling standards body JTC1/SC25 WG3 working group agreed to raise the minimum horizontal cabling requirement. The new standard is stated in ISO/IEC 11801-2. Office space requirements change from Class D (Category 5e) to Class E (Category 6). It includes a recommendation for Class EA (Category 6A). Cat 6A will enable a smooth migration to 2.5, 5, and ultimately 10 gigabits per second (Gbps). In the drafts of 11801-5 (data centers) and 11801-6 (distributed services), the minimum requirement is already Class EA cabling.

Ethernet and IP communications everywhere

The original ISO/IEC 11801 standard enabled the explosive growth and mass deployment of Ethernet and IP communications everywhere. In its first edition, the author says the standard defined Class D balanced cabling based on Category 5 copper components. This standard offered an upgrade path from 10 to 100 megabits per second (Mbps) up to 100 meters. At that time, some experts and industry observers argued that 100 Mbps (100BASE-T) to the desk was overkill for the typical office user.

handful of cablesToday, 100BASE-T technology is in a rapid market decline. 100BASE-T is being replaced with 1000BASE-T (1 Gbps) according to the article. 1000BASE-T is commonplace for desktop and laptop PCs. It also benefits a wide range of other devices such as phones, cameras, and wireless access points (WAPs).

The 11801 standard now includes more cabling classes that were introduced to enable support of up to 10 Gbps. The new classes include Class E (Category 6), Class F (Category 7). Even more recently, Class EA (Category 6A) and Class FA (Category 7A).

Technology trends

According to the CommScope blog, a number of technology trends made ISO choose to upgrade the minimum recommendation for horizontal cabling in offices. Some of the trends recognized by the committee that are driving the adoption of speeds beyond one Captain Ethernetgigabit on the horizontal cabling include:

The rapid growth of BYOD is driving infrastructure upgrades to accommodate IEEE 802.11ac. As I have covered before, new IEEE specifications are being developed to accommodate 802.11ac wireless. 2.5GBASE-T is targeted at installed Class D cabling and 5GBASE-T is targeted at installed Class E cabling. It is expected that a sizable percentage of the installed base will be able to support the faster speeds, however, some installed Class D and Class E systems may require some mitigation steps.

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Ralph Bach has been in IT long enough to know better and has blogged from his Bach Seat about IT, careers, and anything else that catches his attention since 2005. You can follow him on LinkedIn, Facebook, and Twitter. Email the Bach Seat here.

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| April 9, 2015
Comments Off on 802.3bt More Power to the People’s Devices

802.3bt More Power to the People’s Devices

802.3bt More Power to the People's DevicesPower over Ethernet (PoE) powers more than one million end devices today. To continue PoE’s success, the IEEE is answering the market’s demands for more power by developing 802.3bt the third generation of PoE.

The first generation of PoE (2003), 802.3af delivered 12.95 Watts. The second generation, 802.3at (2009) provides 25.5 Watts to the equipment. The new version of PoE will address the need for higher-power PoE. The IEEE has proposed a new standard, 802.3bt, which promises to double the power output of the current 802.3at standard. The new 802.3bt standard, scheduled to be released in 2017, will also adjust PoE to work with 10Gbase-T.

IEEE logoCabling Installation & Maintenance Magazine provides an excellent overview of the new standard. They report that the IEEE 802 LAN/MAN Standards Committee which develops and maintains networking standards like Ethernet, VLANs, and Wireless LAN, is developing the new standard. The DTE Power via MDI over 4-Pair Task Force is working to specify a set of next-generation PoE specifications, and the levels of power likely to be delivered ultimately via the 802.3bt standard will still work on twisted-pair cable, possibly as a four-pair PoE specification which could improve energy efficiency and offer greater power.

New POE Applications

IndustryApplicationTypical Power Consumption
HealthcareNurse call system30-50W
RetailPoint of sale system30-60W
BankingIP Turrets45W
Building ManagementVariable air volume controllers, Access controllers40-50W
Enterprise ITThin clients, Virtual desktop terminals50W
HospitalityPOE switches45-60W
Premise SecurityPTZ cameras30-60W
IndustrialBrushless drives, Motor control>30W
VariousDigital signage>30W
VariousMultichannel wireless access points>30W
via CommScope

The new PoE standard will support 10GBase-T. The 10GBase-T standard uses all 4 pairs to send data. These facts will force the IEEE 802.3bt committee to figure out how to keep the power from interfering with the data on the same wires to supply a minimum of 49 watts at the powered device. One of the key parameters the article mentions is to limit pair-to-pair current imbalance.

POE logoOther goals for the 802.3bt standard are: to be backward-compatible with “af” and “at.” and increased energy efficiency. According to the article, a global move to 4-pair POE systems would create potential energy savings of 60.8 million kilowatt-hours which would prevent greenhouse gasses from 66 million pounds of coal saved annually.

Paul Vanderlaan, technical manager of cable maker Berk-Tek – Nexans’ advanced design and applications lab and other cabling-industry technical experts believe that 802.3bt’s support of 10GBase-T means that the minimum twisted-pair cabling system requirement will increase.  In order to support 10GBase-T, it seems likely that a Category 6A system will be the recommendation. The author notes that the IEEE does not address cabling performance, that is the focus of groups like the TIA or ISO/IEC.

The transition to the new PoE standard will not be simple. CommScope published a white paper where they explain:

Category 6A cabling… Category 5e cabling only provides the minimum level of performance required. Therefore, it is recommended to use Category 6 or Category 6A cabling-preferably solutions … 

Berk-Tek’s Vanderlaan explained why Category 6A cabling is the preferred system. He summarizes the electrical-engineering calculations;

As a general rule, increased copper content, or larger gauge size, will aid in power delivery … when you migrate … you should see larger gauge sizes and more copper content.

system performance characteristicsUnder the new standard users will have to pay attention to new cabling-system performance characteristics like DC resistance unbalance and pair-to-pair resistance imbalance.  The higher wattage’s up to 1 full amp (1,00 milliamps) will present challenges to performance requirements. Mr. Vanderlaan told Cabling Installation & Maintenance Magazine:

For users, cable selection will be based not just on the speed that can be supported, but rather on speed as well as power delivery. What you simply plug in today, you may want to also power in the future.

A new challenge cable plant owners will have to consider is heat. CommScope explains that heat generated within bundles of cables supporting IEEE 802.3bt could rise enough to effect performance.

ambient temperature… the temperature of the cabling will rise due to heat generation in the copper conductors  … the temperature of the cable bundle higher than the ambient temperature of the surrounding environment … The IEEE 802.3bt four-pair PoE standard is expected to assume a maximum temperature rise of 10 degrees Celsius (50 degrees F) when all four pairs are energized … the ambient temperature should not exceed 50 degrees Celsius (122 degrees F) … CommScope recommends Category 6A cabling for four-pair PoE applications. Because increased thermal loading can also increase insertion loss, the maximum cable length should be de-rated for higher temperatures, per ANSI/TIA-568-C.2.

Several vendors have already released pre-standard device-powering systems to meet users’ current needs.

As in the pre-PoE standard days, Cisco (CSCO) has marketed proprietary PoE systems since 2011. Cisco’s Universal Power Over Ethernet (UPOE) technology, which delivers 60 watts of power to devices powered by the Catalyst 4500E; some of those devices include Cisco IP phones, personal telepresence systems, compact switches and wireless access points.

Also, the non-standard Power Over HDBase-T (POH) was introduced by the HDBase-T Alliance a trade group that promotes and standardizes HDBase-T technology for whole-home distribution of uncompressed high-definition (HD) multimedia content. This system delivers up to 100 watts of power to TVs and other devices over distances up to 100 meters/320 feet via one Category 5e or 6 cable with standard RJ45 connectors.

rb-

The new standard is a welcome addition to the toolkit. Cost savings is one of the appeals to PoE. On many projects, PoE low voltage contractors can do the work rather than electrical contractors. If the new system pushes the maximum rate to 75W at the devices as some predict, with there be a backlash from the EC’s and authorities having jurisdiction? Time will tell.

In the meantime, the article says owners and managers should check their current infrastructure with eyes toward how the next generation of devices might be powered via more-capable PoE technology.

Of course, it is always a good idea to pull out your acceptance documentation to understand the installed base of the cable and the likelihood that the cable has the electrical performance characteristics required to support the next generation of PoE.

Related articles

 

Ralph Bach has been in IT long enough to know better and has blogged from his Bach Seat about IT, careers, and anything else that catches his attention since 2005. You can follow him on LinkedIn, Facebook, and Twitter. Email the Bach Seat here.

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| December 17, 2013
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Wiring Closet 3.0

Wiring Closet 3.0The lowly wiring closet at the edge of the network is evolving. You know the one’s that IT shares with the custodians or the women’s lav. The neglected place that connects all end-points into the enterprise network infrastructure. Throughout my career we have moved from 3Com SuperStack hubs to 10/100 SuperStack switches to 100/1000/10000 Cisco 2960’a fixed Ethernet devices. In this first edge era, the primary buying criteria was the price per port. Low price was the critical factor. These devices might have had a few network services but they only provided best-effort connectivity services with little to no operational control according to Nick Lippis in the Lippis Report 103: Wiring Closet Switches Gain Strategic IT Value Label.

Baystack stackCommoditized network gear created enterprise networks consisting of equipment from different vendors. Purchases throughout the wiring closets, distribution, and core were based mainly on cost. The article says that equipment from multiple vendors is the hallmark of Wiring Closet 1.0. Wiring Closet 1.0 made effective management difficult. Multiple management systems required that organizations keep a large staff with diverse skills to keep up network functionality.

Wiring Closet 2.0

Most organizations are now in the Wiring Closet 2.0 era. As competition drove margins on edge switches into the single digits, the author states that vendors began to add services to a new breed of device. The new features on 2.0 switches created new ways for the vendors to compete on different (rb- and more profitable) fronts beyond price per port. Mr. Lippis argues enterprise trends are forcing IT executives to check projects, programs, and priorities as they seek to drive down Total Cost of Ownership (TCO) while extracting added value from their enterprise network. Business executives expect their IT departments to meet continually growing demands without significant year-over-year network expenditures. (rb– the ever popular more with less argument) The article says the new realities include new mixed traffic patterns and increased desktop bandwidth requirements for new applications, communications, and data center strategies.

Goddard rocket scientistSwitch vendors recognized these trends. They responded by developing a new type of wiring closet switch. Second-generation switches added significant functionality. The vendors’ goal is to transform the commoditized network edge (rb- low profit) into a strategic IT asset (rb- high profit). The blog says these new switches enable a host of new applications for Wiring Closet 2.0.

  • Quality of Service: Wiring Closet 2.0 switches tag applications like IP telephony and Unified Communications at access to guarantee priority throughout an internal network and active monitoring
  • Power Over Ethernet (PoE): Second generation, wiring closets distribute power over Ethernet cables. POE enables new classes of devices to be powered from the Wiring Closet 2.0. These demands include WLAN access points, video surveillance, and IP phones. As well as specialty devices such as health care instrumentation, point of sale devices and soon even laptops.
  • Security: The network edge Is the first level of defense. Network Access Control (NAC) and application policing have increased in importance. They are needed to protect the integrity of the network, data privacy, and compliance. Wiring Closet 2.0 switches integrate security features and the support of security appliances bolstering defense-in-depth strategies.
  • Wireless Local Area Networking: WLAN integration, which includes access point, PoE, and controller support, increases WLAN coverage. Further common network management interfaces streamline operational support for both wired and wireless networks.
  • Unified Communication (UC): UC support via PoE to power IP phones and UC end-points plus unique UC configuration profiles to ensure reliable and stable UC operation.
  • Application Intelligence: Application intelligence or the categorizing of applications as they enter the wiring closet and either mark them with QoS or discard the application. This enables application policing at the network edge.
  • Layer 3: Full layer 3 forwarding enabling all the value associating with routing including segmentation and aggregation are now included in some wiring closet switches.
  • Total Cost of Ownership: The network edge and wiring closet switches in particular have a TCO breakdown of 20% capital spend and 80% operational spend according to Gartner (IT). Mew wiring closet switches are more expensive from a capital acquisition point of view. However, their operational cost is lower. Thus, the total dollar spend over a three-year period will also be lower while delivering increased value to the enterprise.

Wiring Closet 3.0

The IT industry is on the verge of a new era at the network edge. New technologies and requirements will disrupt Wiring Closet 2.0.

  • 10Gbps Ethernet: 10Gbps Ethernet is the future of networking. If the past is a guide to the future, then over time more and more 1 Gbps Ethernet ports will upgrade to 10 Gbps. This will place a strain on wiring closet packet processing performance while driving up 10Gbps port density requirements plus downstream distribution and core switch capabilities.
  • Software-defined networking (SDN): The holy grail of SDN is to separate the network control plane from the data plane. The model I carry in my head is wireless networks. There is a central controller that tells the WAP’s what to do and they do their job without any help from the central controller. This implies that the network devices can be dumber and cheaper.
  • Network Management: Consistent network management means leveraging the same supplier for the network edge, distribution, and core.
  • True Layer 3 Support: To support all the above-mentioned trends and unforeseen applications, wiring closet switches need to support full layer 3 forwarding.
  • Support of UC, Mobility, and Security: This basis of competition is one of the most important attributes to the new network edge. Wiring closet switches need to support both standard interfaces and services for UC, mobility, and security so that mixed vendor solutions may occur.
  • IPv6: If you have wiring closets full of perfectly good Layer 2 switches, there’s no reason to replace them just because you can’t manage them with IPv6. If they work today, they’ll work until they break, and you don’t need to worry about (or budget for) swapping them out any sooner.

IPv6

IPv6

Dan Campbell, President, Millennia Systems, Inc. suggested in a recent CircleID post that to manage the move to an IPv6 enabled Wiring Closet 3.0. Organizations should strive to use theIPv6 dual-stack migration strategy. This is where IPv6 is added to the existing systems so they can simultaneously function with both IP versions. Tunneling and translation techniques should be used when the dual-protocol configuration is not possible. The mantra of “dual stack where you can, tunnel where you must” is the order of the day.

He advises that starting today, don’t buy another box unless it supports dual-stack operation or offers a clear, well-defined upgrade plan. It doesn’t matter if the manufacturer is “up and to the right” in the latest Gartner (IT) report; anything you buy from now on that is IPv4-only is a waste of valuable resources.

Mr. Campbell tells network administrators that while LAN switches function mainly at layer 2. They forward Ethernet frames regardless of whether the packet inside is IPv4 or IPv6. There are some functions on a switch that works at layer 3 or higher. They include:

• Dynamic ARP Inspection (DAI).
• DHCP Snooping.
• Multicast Listener Discovery (MLD) Snooping (the IPv6 equivalent of IGMP Snooping).
• Quality of Service (QoS) marking for upstream Differentiated Services treatment.
• Access Lists (e.g., VLAN or regular ACLs).

He explains that these features need layer 3 or upper-layer information; Layer 3 is needed to inspect the packet header or payload inside the Ethernet frame. These features may not be things you are doing now, but you never know when you will. Security requirements and hardening guidelines are recommending things like DAI, DHCP Snooping, and ACLs at the access layer.

The more streaming video gets moved to IP networks, the more the need for multicast. MLD Snooping is necessary to improve performance. Finally, the continued convergence of voice, video, and other rich media and interactive applications to IP networks is furthering the need for QoS. It is always best to mark traffic as close to the edge as possible.

Related articles

Ralph Bach has been in IT long enough to know better and has blogged from his Bach Seat about IT, careers, and anything else that catches his attention since 2005. You can follow him on LinkedIn, Facebook, and Twitter. Email the Bach Seat here.

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| September 12, 2013
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PoE Overworked

PoE OverworkedGary Audin at No Jitter warns that Power over Ethernet (PoE) is not always a plug-and-play environment and PoE should be monitored, managed, and efficient. In this article, Mr. Audin observes that PoE has evolved into an electrical power device utility platform. POE started out as a centralized power source for IP phones, backed up with an Uninterruptible Power Supply (UPS). (rb- Click here and here for my overview of PoE) Since those early Cisco dominated days. The article says PoE now is called upon to support wireless access points; environmental controls; point, tilt, and zoom cameras; lighting control; clocks; door controls; Bluetooth devices; RFID; now laptops, and still more to come.

The LAN switch is the PoE source, but the article warns it can be overwhelmed with the power drain, which produces headaches for IT. Unless properly managed, the PoE function can experience:

  • power drainA blown-out power supply. Smoke is an indicator of this condition.
  • Reduced power to all devices with degraded service from all the attached devices.
  • An added PoE device does not work.
  • The more power is drawn by PoE, the shorter the UPS battery life. The original UPS design could last 20 minutes. Added PoE devices could shorten this to 3 minutes.

PoE IP phones and other devices can signal to the PoE network what class of device it belongs to and how much power it may need. Class 0 devices, usually older devices, do not indicate their PoE power requirements. These devices may draw any power level from none to maximum. The other standard classes, 1-3, range from very low power to mid-level power consumption.

Class 4 is a newer class of device requiring PoE+ (802.1at) and needs to draw more than the 12.95 Watt maximum provided by the original standard PoE. Class 4 devices must be powered by PoE+ ports and may not function correctly on an 802.3af PoE port. Most IP phones are in class 2. IP phones with color screens and other advanced features may be categorized as class 3 devices.

PoE classes

PoE Access Points Wireless LAN access points are also common PoE devices, many of which started out as class 2 and 3 devices. As the wireless speeds increased, so did the power requirements. The 802.11ac standard means that the access points (AP) will have a 1 Gbps connection back to the switches and routers.

site-surveyAt issue is the PoE required. It is likely that each AP could need 20 to 30 watts, the limit that the 802.1at PoE+ standard delivers. Many installed switches cannot support PoE+. So the enterprise has to buy new switches or power supplies or power injectors. (rb- add this to your site-survey when you plan to implement 802.11ac)

Mr. Audin spoke to Tim Titus, CTO, and founder of PathSolutions, (they happen to sell a network management tool) about what he considers a good approach to monitoring and managing POE. He told No Jitter,

“Regardless of whether there are any PoE or PoE+ devices on a network, it can be very helpful to monitor the health of our network equipment’s power supplies. The best monitoring system watches the status and power consumption of each power supply, what percentage of utilization it is running, and which interfaces are drawing power, so power policing can be achieved.”

He provided this example of missing power management.

“Keeping an eye on power supplies avoids unpleasant discoveries. One unlucky network administrator had two power supplies installed in a network chassis (one primary and one backup). Unfortunately, when the primary power supply stopped working, nobody knew, since the backup power supply was doing its job of keeping everything running. The problem wasn’t noticed for over six months. Nobody was in the empty remote wiring closet to notice the lack of lights on the power supply. The users remained blissfully unaware of impending doom until the wee hours of a weekend when the second power supply was shut off by a circuit-breaker trip!” 

Mr. Titus pointed out to Mr. Audin, that monitoring should happen at the port level,

“Not only will a monitoring system show you what mode a PoE port is operating in, but it should also provide a view of relevant error counters.

  • MPS Absent and Invalid Signature errors frequently point to broken or defective powered devices.
  • Overload conditions and short-circuits typically point to wiring problems (or somebody re-wiring devices in use).
  • Denied errors can point to devices asking for more power than the switch has available, and may indicate that it is time to consider adding another power supply to a large Ethernet chassis.”

How did that happen?

Finally, many network engineers try to buy limited PoE due to the cost premium of POE ports, only to find that half of their PoE ports are used by non-PoE devices such as PCs. With a monitoring tool, the engineers could have avoided buying expensive PoE ports or purchased less expensive “ordinary” Ethernet ports.  The engineers should have an up-to-date PoE port inventory and use it to avoid over-buying the PoE by playing safe in their design. (rb- Been there done that, I’ve been in many customer’s closets and found POE switches full of PC and printer access ports.)

rb-

The author warns not to assume that PoE is always a plug-and-play environment. PoE should be handled like a utility–monitored, managed, and efficient.

I have tried to build custom fields by working with reports in SolarWind’s Orion by working with MIBs, it’s not the funnest thing in the world. I wonder if this product does a better job.

Related articles

 

Ralph Bach has been in IT long enough to know better and has blogged from his Bach Seat about IT, careers, and anything else that catches his attention since 2005. You can follow him on LinkedIn, Facebook, and Twitter. Email the Bach Seat here.

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| April 5, 2012
Comments Off on Power over Ethernet 802.3af

Power over Ethernet 802.3af

Power over Ethernet 802.3afA client recently asked what happened to the network design rule of thumb which said do not install data cables anywhere near electrical cables? The fear of cross-talk, interference, and corruption of the data traffic seems to have disappeared with Power over Ethernet (PoE). He rightly pointed out that now it seems OK to mix data and power in the same cable going to a networked device. 

Read part 2 here.

Plain Old Telephone SystemPoE is similar in principle to the way that the copper wire pair that carries your POTS (Plain Old Telephone System) telephone signals into your house also carries enough electricity (48v DC) from the telco Central Office to power the phone’s core elements of the headset, dial, and ringer. Power over Ethernet’s development started with early implementations of Voice over Internet Protocol VoIP)phone systems. VoIP pioneers did not have a telco CO to power the phones and powering the VoIP phones with wall warts proved unreliable. The phones stopped working when unplugged from the wall or if the building lost power.

In 2000 Cisco (CSCO) developed the first successful technique of putting 48v DC on the LAN data cable along with the data traffic. This proprietary system allowed Cisco to overcome customer objections to wall warts and sell a lot of VoIP systems.

Cisco logoCisco’s original PoE equipment was capable of delivering up to 10W per port. The endpoint and the Cisco switch negotiated the amount of power to be delivered based on a power value in the proprietary Cisco Discovery Protocol (CDP). The Power Sourcing Equipment (PSE) will send a Fast Link Pulse (FLP) on the transmit pair. The Powered Device (PD) connects the transmit line to the receiving line via a low pass filter. And thus the PSE gets the FLP in return. Cisco’s original PoE implementation is not software upgradeable to the IEEE 802.3af standard. Cisco manufactured many IP phones and WLAN access points devices that were not compliant with the IEEE 802.3-2005 Clause 33 including:

Cisco pre-standard IP phones
7985G7960G7940G7910G7910G + SW
7912G7905G7902G7970G
Cisco IEEE 802.3af and pre-standard IP phones
7970G7961G7906G7941G
7911G7962G
The Cisco 7936 Conference Phone does not support any LAN based power and requires a Cisco power injection adapter
Source

Throughout 2001 and 2002, other VoIP and Wireless Access Point (WAP) vendors saw Cisco’s success and developed their own proprietary (and often non-interoperable) powering systems. As more proprietary systems were developed the Institute of Electrical and Electronics Engineers (IEEE) recognized the need to standardize PoE. The IEEE 802.3 Ethernet Committee assigned PoE technology to a new working subcommittee called 802.3af. The IEEE working group’s charge was to create a standardized version of the Power Over Ethernet so that any manufacturer who wanted to could make their products PoE ready. The IEEE working group took commentary from 2001 to 2003 and released the ratified IEEE 802.3af-2003 Power over Ethernet standard in June 2003 which added clause 33 to the IEEE 802.3 standard

Institute of Electrical and Electronics Engineers (IEEE) 802.3 Ethernet CommitteeThe 802.3af document describes how PoE systems should work.  The standard defines two types of PoE equipment, Power Sourcing Equipment (PSE) and the Powered Device (PD). Power Sourcing Equipment sends the power out over the LAN cabling system to the Powered Device. The PSE would send out a maximum of 15.4 watts DC per link to each device, (limited to standard Ethernet distances). 12.95 watts are assumed to be available at the PD because some power is lost in the cable.

The nominal voltage is 48 V, over two of the four available pairs on a Cat. 3/Cat. 5e cable. “Phantom power” is used to allow the powered pairs to also carry data. This permits PoE to be used with 10BASE-T and 100BASE-TX, which use only two of the four pairs in the cable, but also with 1000BASE-T (gigabit Ethernet), which uses all four pairs for data transmission. This is possible because all versions of Ethernet over twisted pair cable specify differential data transmission over each pair with transformer coupling; the DC supply and load connections can be made to the transformer center-taps at each end. Each pair thus operates in “common mode” as one side of the DC supply, so two pairs are required to complete the circuit. The polarity of the DC supply may be inverted by cross cables; the powered device must work with either pair: spare pairs 4-5 and 7-8 or data pairs 1-2 and 3-6. Polarity is required on data pairs and ambiguously implemented for spare pairs, with the use of a bridge rectifier. (Source)

VOIP devicesPower Sourcing Equipment can be in two form factors. A PSE can be implemented as an endspan which is an Ethernet switch with powered ports (a PoE enabled switch) or midspan which is a power hub that is used along with a non-powered switch the end-user already has in place. PD’s can receive PoE equally well from either type of PSE per the standard. The decision to use an endspan or a midspan is left up to the end-user.  The end device can use either powering technique.

The Powered Device (PD) is a network device like VoIP phones, Wireless Access Points, and IP cameras. which are capable of taking the power off the LAN cable, through the RJ-45 (8P8C) connector and using it to power itself. Some pre-standard PoE devices are incompatible with 802.3af equipment. More PoE ready PD’s are available every year  PoE ready end devices can reduce installation costs by as much as 90% over traditional powering techniques.  Among the newer PoE PD’s devices on the market or coming soon are IP Paging, Speaker Systems, POS Terminals, Door and Gate Security hardware, Public Information signs, Building Access, Temperature Control Systems, Stage Lighting, and Computers. These newer PD’s were pushing 802.3af to its limits and the IEEE began work to evolve the standard. This power limitation prevented “high power” devices that required up to 30W to be supported via the industry-standard PoE solution.

Related articles

 

Ralph Bach has been in IT long enough to know better and has blogged from his Bach Seat about IT, careers, and anything else that catches his attention since 2005. You can follow him on LinkedIn, Facebook, and Twitter. Email the Bach Seat here.

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