Protocol Specification - 3Com S7906E Configuration Manual

1) PoE power: The whole PoE system is powered by the PoE power.
2) PSE: A PSE is a device supplying power for PDs. A PSE can be built-in (Endpoint) or external
(Midspan). A built-in PSE is integrated in a switch, and an external PSE is independent from a
switch or router. The PSEs of 3Com are built in, and can be classified into two types:
Device with a single PSE: Only one PSE is available on the device; so the whole device is
considered as a PSE.
Device with multiple PSEs: For a device with multiple PSEs, an interface board with the PoE
power supply capability is a PSE. The system uses PSE IDs to identify different PSEs. You can
use the display poe device command to display the mapping between a PSE ID and the slot
number of an interface board.
Before the S7900E series Ethernet switch configure the IRF, the formula for calculating PSE IDs
is as follows: the slot number of LPU x 3 + 1. For example, if the slot number is 3, the PSE ID is 3 x
3 + 1.
After the S7900E series Ethernet switch configured the IRF, the formula for calculating PSE IDs is
as follows: the slot number of ((chassis-1) x 14 + slot number of LPU) x 3 + 1. For example, if the
chassis number is 3 and the slot number is 4, the PSE ID is ((3-1) x14 + 4) x 3 + 1.
A PSE can examine the Ethernet cables connected to PoE interfaces, search for PDs, classify them,
and supply power to them. When detecting that a PD is unplugged, the PSE stops supplying power to
the PD.
3) PI: An Ethernet interface with the PoE capability is called PoE interface. Currently, a PoE interface
can be an FE or GE interface.
4) PD: A PD is a device accepting power from the PSE, including IP phones, wireless APs, chargers
of portable devices, POS, and web cameras.
The PD that is being powered by the PSE can be connected to another power supply unit for
redundancy power backup.
Figure 1-1 PoE system diagram

Protocol Specification

The protocol specification related to PoE is IEEE 802.3af.
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