QoS-aware Sleep Mode Controller in "Energy Efficient Ethernet"

Energy efficiency in telecommunication networks has been recognized as a very important topic during the last few years. This is motivated by the fact that reduction of power consumption translates into reduction of carbon footprint and operating costs. The IEEE standardization body also included energy consumption aspects into its activities and developed a standard on Energy Efficient Ethernet (IEEE P802.3az). Its objective was to define a mechanism to reduce power consumption of the Physical layer when links are underutilized. It therefore defined a protocol to coordinate transitions to and from a lower power consumption mode without changing the link status and dropping frames. Time required by such transitions is however comparable with packet transmission time; that makes power consumption reduction of the method strongly dependent on packet inter-arrival time and limits its application to cases of low link utilization, such as home/office environments and access networks. A new solution for extending the application of the EEE mechanism in Ethernet networks with different traffic load conditions and QoS requirements, where data flows are statically provisioned and opportunely conditioned at the edge, is proposed. It allows shaping traffic across the network so as to reduce ON/OFF transitions at EEE aware switch interfaces while ensuring end to end delay constraints to packets traversing multiple links. It off-line determines on the basis of the Parekh Gallager theorem if the activation of a dummy flow, associated to the OFF periods, can provide power consumption reduction without impacting data flows delay requirements. On ports where the dummy flow is activated, the scheduler mechanism triggers the OFF period each time a dummy packet is served. A performance analysis of the EEE mechanism enhanced with the proposed QoS aware sleep mode controller has been carried out in order to quantify the improvements in terms of energy efficiency with respect to the standard EEE operation and to assess its effectiveness in terms of Quality of Service (QoS).