Energy Efficient Ethernet

Energey Efficient Ethernet (EEE) or IEEE 802.3az is a great way of saving energy in computer networks, but it creates problems in PTP networks. Somewhat simplified, EEE works by turning off the PHY if there is no traffic around, then turning it on again when there is a packet coming. If the PHY needs to wake up when a sync message comes, the sync message will be delayed for longer time than if the PHY was already awake when the sync message comes. This will create huge packet delay variation, which in turn makes it extremely difficult for a slave to recover the clock. 

EEE is negotiated between PHYs and as Qulsar devices has EEE turned off in our devices, EEE will never be applied between our device and a switch or other device supporting EEE. However in a scenario with multiple switches supporting EEE between the PTP master and slave, it's important to make sure EEE is turned off in these switches, at least for the ports where PTP traffic is anticipated.

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