Energy-aware path selection for scheduled lightpaths in IP-over-WDM networks

Abstract

Abstract-Traffic grooming, i.e. the aggregation of multiple traffic streams on one channel or wavelength, has often been considered in the context of reducing blocking and improving capacity utilization. More recently, traffic grooming has also been advocated in the context of energy-aware routing. In this paper we study energy-efficient path selection under the scheduled traffic model in IP-over-WDM optical networks. We show that there is indeed a strong relation between traffic grooming and energy efficiency, but also that it sometimes pays off not to groom. We propose an energy-aware routing algorithm that is based on traffic grooming, but which has the flexibility to deviate from it where needed. Our approach can be applied to networks with and without wavelength conversion. Simulations show that our energy-aware routing algorithm both brings significant energy savings as well as a lower blocking probability in comparison to a shortest paths based routing algorithm and a traffic grooming algorithm. I. INTRODUCTIONIn wavelength division multiplexing (WDM) technology, the capacity of a fiber is divided into several non-overlapping wavelength channels that can transport data independently. These wavelength channels make up lightpaths that are used to establish optical connections that may span several fiber links. With current commercial technology, each lightpath can be independently operated at data rates of several Gb/s. However, traffic between a pair of nodes may not be able to fill up the available bandwidth of a lightpath. In order to efficiently utilize the available bandwidth, several independent traffic streams can be aggregated to share the capacity of a lightpath. This is known as traffic grooming (e.g., see [1]). While traffic grooming has obvious potential to increase throughput, the grooming of traffic may also lead to energy efficiency, although this is not always the case. The main contributions of this paper are (1) a model for energy consumption in IP-over-WDM networks, (2) an energy-aware algorithm, for allocating scheduled lightpaths, that finds the best balance between traffic grooming or setting up a new lightpath, and (3) a simulative study to the effect of introducing wavelength conversion on the overall blocking probability and consumed energy.The remainder of this paper is organized as follows. Section II presents related work. Section III describes our network model and analyzes the energy consumption with traffic grooming and when setting up a new lightpath. An energyaware routing algorithm for dynamic traffic is proposed in Section IV. Dynamic traffic refers to requests that come in an