Dynamic Energy Management for IP-over-WDM Networks

This paper proposes a new energy management framework for an IP over WDM network. A key constraint of our architecture is to maintain the logical IP topology while saving energy by infrastructure sleeping and virtual router migration. Since the traffic in a network typically has a regular diurnal pattern based on people’s activities, some virtual routers can be moved to a smaller set of physical router platforms so that the unused physical platforms can be switched off when the traffic demand is light. As the traffic demand increases the sleeping physical router platforms can be re-awoken and the virtual router functionality returned to the original physical platforms close to where the traffic load is rising. Since the IPlayer topology remains unchanged throughout the virtual router migration, there is no network disruption and discontinuity when the physical platforms enter or leave hibernation. However, this migration can place extra demand on the optical layer as additional connections are needed to preserve the logical IP topology whilst forwarding traffic to the new virtual router location. As these additional optical connections are used to forward traffic from the sleeping node to the remote location where the virtual router is present, this is akin to traffic grooming and the burden on the optical layer is greater the further the new router instance is from its original default location (where it still perceives itself to be). Although published work has hitherto considered how to migrate virtual routers from one physical platform to another, the goal has been to avoid downtime whilst the network undergoes planned maintenance. This paper considers virtualisation in the context of an energy saving architecture; and addresses the question of when to migrate, where to migrate to, and the means by which underlying optical connections are utilised.