Chapter 4. Web Configuration & Operation
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CHAPTER 4
WEB OPERATION & CONFIGURATION
4.3.2 Green Ethernet Configuration
Configure EEE (Energy-Efficient Ethernet) as well as Ethernet power savings on copper ports.
Port Power Savings Configuration
Optimize EEE for:
Enables/disables the EEE function for this switch. The two options are:
Power:
The EEE function is enabled. This is the default setting.
Legacy:
EEE is not enabled.
Port Configuration
ActiPHY™:
ActiPHY™ works by lowering the power for a port when there is no link. The port is power up for short
moment in order to determine if an Ethernet cable is inserted. For ports with no cable connection, the PHY remains
powered down to save energy.
PerfectReach™:
PerfectReach™ is another power saving mechanism. PerfectReach™ works by determining the cable
length and lowering the Ethernet transmit power for ports with short cables.
EEE (Energy-Efficient Ethernet):
EEE is a power saving option that reduces the power usage when there is low or no
traffic utilization. EEE was developed through the IEEE802.3az task force of the Institute of Electrical and Electronic
Engineers (IEEE). EEE works by powering down circuits when there is no traffic. When a port gets data to be
transmitted all circuits are powered up. The time it takes to power up the circuits is called wakeup time. The default
wakeup time is 17 us for 1Gbit links and 30 us for other link speeds. EEE devices must agree upon the value of the
wakeup time in order to make sure that both the receiving and transmitting device has all circuits powered up when
traffic is transmitted. The devices can exchange wakeup time information using the LLDP (Link Layer Discovery
Protocol) protocol. EEE works for ports in auto-negotiation mode, where the port is negotiated to either 1G or 100
Mbit full duplex mode. For ports that are not EEE-capable the corresponding EEE checkboxes are grayed out and thus
impossible to enable EEE for.
When a port is powered down for saving power, outgoing traffic is stored in a buffer until the port is powered up
again. Because there are some overhead in turning the port down and up, more power can be saved if the traffic can
be buffered up until a large burst of traffic can be transmitted. Buffering traffic will give some latency in the traffic. For
traffic that should not be held back, urgent queues may be assigned to reduce latency yet still result in overall power
saving.
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