Multi-layer Energy Savings in Optical Core Networks

We propose a multi-layer energy saving technique for optical core networks that aims at reducing energy consumption by powering off components in different layers of the network. After obtaining satisfactory results in saving energy by powering off ports in the IP layer in our previous work, in this paper we target more savings by considering additional layers in the network. The model proposed in this paper is a heuristic that bases the capacity prediction for a future time slot on the number of 40G links needed in the current time slot. It also revolves around four parameters for which the values are empirically set. We set two thresholds, low and high, as well as the number of links to power off or power on each time the utilization is below or above a threshold. We assess our model through experiments featuring an Internet2-like topology and a real one-day worth of traffic split into five-minute time slots. The results offer a comparison between different parameters settings and how they affect energy savings and the number of overflows in the network that result from mis-prediction. That said, we demonstrate that our model can achieve up to 90% reduction in energy consumption in the best case when the future traffic is known; otherwise, the savings can range between 82% and 88%, with the occurrence of a small amount of traffic overflow events

Facing the Reality: Validation of Energy Saving Mechanisms on a Testbed

Two energy saving approaches, called Fixed Upper Fixed Lower (FUFL) and Dynamic Upper Fixed Lower (DUFL), switching off idle optical Gigabit Ethernet (GbE) interfaces during low traffic periods, have been implemented on a testbed. We show on a simple network scenario that energy can be saved using off-the-shelf equipment not explicitly designed for dynamic on/off operation. No packet loss is experienced in our experiments. We indicate the need for faster access to routers in order to perform the reconfiguration. This is particularly important for the more sophisticated energy saving approaches such as DUFL, since FUFL can be implemented locally

A Dynamic Local Method for Bandwidth Adaptation in Bundle Links to Conserve Energy in Core Networks

Energy savings in bundle links of the core network has been investigated recently. The bundle link technique is widely used in current core networks to provide higher bandwidth and more resilience. Basically a bundle link is composed of several high-speed physical sublinks which could be SONET connections, Ethernet circuits, etc. in order to make them work together as a virtual connection. In current network operations, all of the sublinks are activated if the bundle link is powered on although the sublinks could be shut down or brought up independently. Smartly and dynamically shutting down and bringing up sublinks and their attached ports according to the traffic demand or estimation could greatly increase the link utilization and save a large amount of energy. In previous work, we proposed a local heuristic threshold-based method to explore the potential energy savings in core networks by adjusting the number of active sublinks in the bundle links. In this paper, we further explore the possibilities to reach a better tradeoff between energy-saving performance and congestion risk by setting different value combinations of two parameters: the utilization threshold and sublink-adding strategy. From that, we propose a dynamic and hybrid local heuristic threshold-based algorithm, which we call HDLHT algorithm, to achieve a better tradeoff between energy-savings and congestion risk. In HDLHT algorithm, the bundle links are given different combinations of these two parameters according to the burstiness of their traffic. A simulation experiment deploying HDLHT algorithm was conducted on a synthetic network and the results show that HDLHT can greatly reduce the number of congestion occurrences with limited decrease in energy savings

Energy aware traffic engineering

Over-provisioning of network resources, i.e., routers and links, provides a unique opportunity for energy aware traffic engineering. In the thesis, we design three heuristic approaches, i.e., SSPF, MSPF, and 2DP-SP to solve three proposed green routing problems, i.e., SP-EAR, MP-EAR, and EAR-2DP. Our simulation results show the trade-off between power savings and network performances, i.e., maximum link utilization, path length, and route reliability, when using green routings algorithms