Dell PowerConnect 55xx Systems User Guide 17
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•IP Gateways
•PDAs
• Audio and video remote monitoring
For more information, see "Power over Ethernet" on page 162. 
Green Ethernet 
Green Ethernet, also known as Energy Efficient Ethernet (EEE), is an effort 
to make networking equipment environmentally friendly, by reducing the 
power usage of Ethernet connections. 
The Short-Reach method, which reduces power over Ethernet cables shorter 
than 40m, is supported by the device.
For more information, see "Green Ethernet Configuration" on page 391. 
Head of Line Blocking Prevention
Head of Line (HOL) blocking results in traffic delays and frame loss caused 
by traffic competing for the same egress port resources. To prevent HOL 
blocking, the device queues packets, and packets at the head of the queue are 
forwarded before packets at the end of the queue.
Flow Control Support (IEEE 802.3X)
Flow control enables lower-speed devices to communicate with higher-speed 
devices, by requesting that the higher-speed device refrain from sending 
packets. Transmissions are temporarily halted to prevent buffer overflows.
For more information, see "Flow Control" on page 387.
Back Pressure Support
On half-duplex links, the receiving port prevents buffer overflows by 
occupying the link so that it is unavailable for additional traffic.
For more information, see "Protected Ports" on page 395.