Using coordinated transmission with energy efficient ethernet

Abstract

IEEE 802.3az Energy Efficient Ethernet (EEE) supports link active and sleep (idle) modes as a means of reducing the energy consumption of lightly utilized Ethernet links. A link wakes-up when an interface has packets to send and returns to idle when there are no packets. In this paper, we show how Coordinated Transmission (CT) in a 10GBASE-T link can allow for key physical layer (PHY) components to be shutdown to further reduce Ethernet energy consumption and enable longer cable lengths. CT is estimated to enable an additional 25% energy savings with a trade-off of an added frame latency of up to 40 μs, which is expected to have a negligible impact on most applications. The effective link capacity is approximately 4 Gb/s for symmetric traffic and close to 7 Gb/s for asymmetric traffic. This can be sufficient in many situations. Additionally a mechanism to switch to the normal full-duplex mode is proposed to allow for full link capacity when needed while retaining the additional energy savings when the link load is low. © 2011 IFIP International Federation for Information Processing.