The Green Ethernet feature available on the ME 1200 Web GUI allows you
to set the port power savings configuration.
Port Power Savings
EEE is a power saving
option that reduces the power usage when there is low or no traffic
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 named wakeup time. The default wakeup time is 17 microseconds for 1
Gbit links and 30 microseconds for other link speeds. EEE devices must agree
upon the value of the wakeup time 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 protocol.
EEE works for ports in
auto-negotiation mode, where the port is negotiated to either 1 G 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.
option to optimize EEE for either best power saving or
least traffic latency.
options are available for
Port: The switch port number of the
ActiPHY: Link down power savings enabled.
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 cable is inserted.
PerfectReach: Cable length power savings
enabled. PerfectReach works by determining the cable length and lowering the
power for ports with short cables.
EEE: Controls whether EEE is enabled for
this switch port. For maximizing power savings, the circuit is not started at
once transmit data is ready for a port, but is instead queued until a burst of
data is ready to be transmitted. This will give some traffic latency.
If desired, it
is possible to minimize the latency for specific frames, by mapping the frames
to a specific queue (done with QOS), and then mark the queue as an urgent
queue. When an urgent queue gets data to be transmitted, the circuits will be
powered up at once and the latency will be reduced to the wakeup time.
Urgent Queues: Queues set will activate transmission of frames as
soon as data is available. Otherwise the queue will postpone transmission until
a burst of frames can be transmitted.