Technical data

292 FastIron Ethernet Switch Administration Guide
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Power over Ethernet overview
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Power over Ethernet overview
This section provides an overview of the requirements for delivering power over the LAN, as defined
by the Institute of Electrical and Electronics Engineers Inc. (IEEE) in the 802.3af (PoE) and 802.3at
(PoE+) specifications.
Brocade PoE devices provide Power over Ethernet, compliant with the standards described in the
IEEE 802.3af specification for delivering inline power. Brocade PoE+ devices are compliant with
both the 802.3af and 802.3at specifications. The 802.3af specification defined the original
standard for delivering power over existing network cabling infrastructure, enabling
multicast-enabled full streaming audio and video applications for converged services, such as,
Voice over IP (VoIP), Wireless Local Area Access (WLAN) points, IP surveillance cameras, and other
IP technology devices. The 802.3at specification expands the standards to support higher power
levels for more demanding powered devices, such as video IP phones, pan-tilt-zoom cameras and
high-power outdoor antennas for wireless access points. Except where noted, this document will
use the term PoE to refer to both PoE and PoE+.
Table 30 lists the FastIron devices and modules that support PoE, PoE+, or both.
PoE technology eliminates the need for an electrical outlet and dedicated UPS near IP powered
devices. With power sourcing equipment such as a Brocade FastIron PoE device, power is
consolidated and centralized in the wiring closets, improving the reliability and resiliency of the
network. Because PoE can provide Power over Ethernet cable, power is continuous, even in the
event of a power failure.
Power over Ethernet terms used in this chapter
The following terms are introduced in this chapter:
• Power-sourcing device or Power-sourcing equipment (PSE) - This is the source of the power, or
the device that integrates the power onto the network. Power sourcing devices and equipment
have embedded PoE technology. The Brocade FastIron PoE device is a power sourcing device.
• IP powered device (PD) or power-consuming device - This is the Ethernet device that requires
power and is situated on the end of the cable opposite the power sourcing equipment.
Methods for delivering Power over Ethernet
There are two methods for delivering Power over Ethernet (PoE), as defined in the 802.3af and
802.3at specifications:
• Endspan - Power is supplied through the Ethernet ports on a power sourcing device. With the
Endspan solution, power can be carried over the two data pairs (Alternative A) or the two spare
pairs (Alternative B).
• Midspan - Power is supplied by an intermediate power sourcing device placed between the
switch and the PD. With the Midspan solution, power is carried over the two spare pairs
(Alternative B).
With both methods, power is transferred over four conductors, between the two pairs. 802.3af-
and 802.3at-compliant PDs are able to accept power from either set of pairs.
Brocade PoE devices use the Endspan method, compliant with the 802.3af and 802.3at
standards.
The Endspan and Midspan methods are described in more detail in the following sections.