On the effects of energy-aware traffic engineering on routing reliability

Current network infrastructures are over-provisioned to increase their resilience against resource failures, e.g., bundled links and nodes, as well as congestion during peak hours. However such strategies waste resources as well as exhibit poor energy efficiency at off-peak periods. To this end, several energy aware routing algorithms have been proposed to maximally switch off redundant network resource at low traffic load to minimize energy usage. These routing solutions, however, do not consider network reliability as critical back-off links/nodes maybe switched off. Henceforth, we aim to quantify the effects of five recently proposed green routing approaches, namely FGH, GreenTE, MSPF, SSPF, and TLDP, on the following two reliability measures: (i) 2-terminal reliability (ii) path reliability. Experiments using three topologies with real and synthetic traffic demands show that switching off redundant links significantly affects the 2-terminal reliability. Routing traffic through multiple paths has lesser reliability impact while reducing energy, especially when the paths are link disjoint. Interestingly, TDLP and MSPF have better path reliabilities than using shortest path routing

Energy management in communication networks: a journey through modelling and optimization glasses

The widespread proliferation of Internet and wireless applications has produced a significant increase of ICT energy footprint. As a response, in the last five years, significant efforts have been undertaken to include energy-awareness into network management. Several green networking frameworks have been proposed by carefully managing the network routing and the power state of network devices. Even though approaches proposed differ based on network technologies and sleep modes of nodes and interfaces, they all aim at tailoring the active network resources to the varying traffic needs in order to minimize energy consumption. From a modeling point of view, this has several commonalities with classical network design and routing problems, even if with different objectives and in a dynamic context. With most researchers focused on addressing the complex and crucial technological aspects of green networking schemes, there has been so far little attention on understanding the modeling similarities and differences of proposed solutions. This paper fills the gap surveying the literature with optimization modeling glasses, following a tutorial approach that guides through the different components of the models with a unified symbolism. A detailed classification of the previous work based on the modeling issues included is also proposed

Power-aware routing in networks with delay and link utilization constraints

This paper addresses the NP-hard problem of switching off bundled links whilst retaining the QoS provided to existing applications. We propose a fast heuristic, called Multiple Paths by Shortest Path First (MSPF), and evaluated its performance against two state-of-the-art techniques: GreenTE, and FGH. MSPF improves the energy saving on average by 5% as compared to GreenTE with only 1% CPU time. While yielding equivalent energy savings, MSPF requires only 0.35% of the running time of FGH. Finally, for Maximum Link Utilization (MLU) below 50% and delay no longer than the network diameter, MSPF reduces the power usage of the GÉANT topology by up to 91%

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