PoE/PoE+ Planning and Implementation Guide 2011-09

1-1
Introduction
Overview
1
Introduction
This chapter provides an overview of:
■ Power over Ethernet (PoE/PoE+).
■ A list of reasons why you might want to implement PoE in your network
environment.
■ How PoE supplies power over twisted pair cable.
■ The capabilities of the devices used to provide PoE.
Overview
Power over Ethernet technology allows IP telephones, wireless LAN Access
Points and other appliances to receive power as well as data over existing LAN
cabling, without needing to modify the existing Ethernet infrastructure.
Power over Ethernet has become a standard feature of ethernet switches, as
the cost of adding power supplies to the Ethernet switches is small. IEEE
802.3af is an extension to the existing Ethernet standards. It offers the first
truly international standard for power distribution (consider how many
different AC power plugs exist worldwide).
Almost all appliances require both data connectivity and a power supply. Just
as telephones are powered from the telephone exchange through the same
twisted pair that carries the voice, we can now do the same thing with Ethernet
devices.