Sleep modes effectiveness in backbone networks with limited configurations

In this work we propose a strategy to minimize the impact of energy saving techniques on the performance of an Internet Service Provider network. We study the problem of putting in sleep mode links of a backbone network, while limiting the number of times each device changes its power state (full power mode or sleep mode). Our aim is to limit the number of network configurations, i.e., the change of the current set of network links at full power. We tackle the problem both analytically and by simulations. We first present a model, based on random graph theory, to compute the links energy saving given a traffic variation, QoS requirements, and the number of allowed network configurations. The same analysis is then repeated over two realistic case studies, and with realistic algorithms to choose the set of links in sleep mode. Results show (both analytically and by simulation) that the energy savings with few configurations (two or three per day) are close to the maximum one, in which a new configuration is applied for each traffic matrix. Moreover, we show that few configurations per day limit the number of overhead messages required for exchanging information about the device state. Thus, we can conclude that a practical implementation of sleep mode strategies for network operators is to define, on the basis of typical traffic trend, few configurations to be activated in specific time instants. (c) 2013 Elsevier B.V. All rights reserved.