802.3az Energy Efficient Ethernet Feature
This section describes the 802.3az Energy Efficient Ethernet (EEE) feature.
It contains the following topics:
802.3az EEE Overview
802.3az EEE is designed to save power when there is no traffic on the link. In Green Ethernet, power is reduced when the port is down. With 802.3az EEE, power is reduced when the port is up, but there is no traffic on it.
802.3az EEE is only supported on devices with GE ports.
When using 802.3az EEE, systems on both sides of the link can disable portions of their functionality and save power during periods of no traffic.
802.3az EEE supports IEEE 802.3 MAC operation at 100 Mbps and 1000 Mbps:
LLDP is used to select the optimal set of parameters for both devices. If LLDP is not supported by the link partner, or is disabled, 802.3az EEE will still be operational, but it might not be in the optimal operational mode.
The 802.3az EEE feature is implemented using a port mode called Low Power Idle (LPI) mode. When there is no traffic and this feature is enabled on the port, the port is placed in the LPI mode, which reduces power consumption dramatically.
Both sides of a connection (switch port and connecting device) must support 802.3az EEE for it to work. When traffic is absent, both sides send signals indicating that power is about to be reduced. When signals from both sides are received, the Keep Alive signal indicates that the ports are in LPI status (and not in Down status), and power is reduced.
For ports to stay in LPI mode, the Keep Alive signal must be received continuously from both sides.
Advertise Capabilities Negotiation
802.3az EEE support is advertised during the Auto-Negotiation stage. Auto- Negotiation provides a linked device with the capability to detect the abilities (modes of operation) supported by the device at the other end of the link, determine common abilities, and configure itself for joint operation. Auto- Negotiation is performed at the time of link-up, on command from management, or upon detection of a link error. During the link establishment process, both link partners to exchange their 802.3az EEE capabilities. Auto-Negotiation functions automatically without user interaction when it is enabled on the device.
NOTE If Auto-Negotiation is not enabled on a port, the EEE is disabled.
Link Level Discovery for 802.3az EEE
In addition to the capabilities described above, 802.3az EEE capabilities and settings are also advertised using frames based on the organizationally-specific TLVs defined in Annex G of IEEE Std 802.1AB protocol (LLDP). LLDP is used to further optimize 802.3az EEE operation after auto-negotiation is completed. The 802.3az EEE TLV is used to fine tune system wake-up and refresh durations.
Availability of 802.3az EEE
802.3az EEE is available on the following SKUs:
SG 300-10. SG 300-10MP, SG 300-10P, SG 300-20. SG 300-28, SG 300-28P and SG 300-52.
Default Configuration
By default, 802.3az EEE and EEE LLDP are enabled globally and per port.
Interactions Between Features
The following describe 802.3az EEE interactions with other features:
- If auto-negotiation is not enabled on the port, the 802.3az EEE operational status is disabled.
- If 802.3az EEE is enabled and the port is going Up, it commences to work immediately in accordance with the maximum wake time value of the port.
- On the GUI, the EEE field for the port is not enabled if EEE is not supported globally.
- If the port speed on the GE port is changed to 10Mbit, 802.3az EEE is disabled. This is supported in GE models only.
802.3az EEE Configuration Workflow
This section describes how to configure the 802.3az EEE feature and view its counters.
- Ensure that auto-negotiation is enabled on the port by opening the Port Management > Port Settings page.
- Ensure that 803.2 Energy Efficient Ethernet (EEE) is globally enabled in the Port Management > Green Ethernet > Properties page (it is enabled by default). This page also displays how much energy has been saved.
- Ensure that 802.3az EEE is enabled on a port by opening the Green Ethernet > Port Settings page.
- Select a port, open the Edit Port Settings page.
- Check the 802.3 Efficient Energy Ethernet (EEE) mode on the port (it is enabled by default).
- Select whether to enable or disable advertisement of 802.3az EEE capabilities through LLDP in 802.3 Efficient Energy Ethernet (EEE) LLDP (it is enabled by default).
- To see 802.3az EEE-related information on the local device, open the Administration > Discovery LLDP >LLDP Local Information page, and view the information in the 802.3az Energy Efficient Ethernet (EEE) block.
- To display 802.3az EEE information on the remote device, open the Administration > Discovery LLDP > LLDP Neighbor Information pages, and view the information in the 802.3 Energy Efficient Ethernet (EEE) block.