Abstract

Part 1: Autonomic and Decentralized Management International audience Energy efficiency has become a major research topic in the Internet community as a result of unprecedented rise in the Information and Communication Technology (ICT) sector. One typical approach towards energy efficiency is to select a subset of IP routers or interfaces that will go to sleep mode during the off-peak period. However, on-the-fly network reconfiguration is generally deemed harmful especially to real time packets due to routing re-convergence. In this paper, we develop an efficient algorithm for achieving energy efficiency which is disruption free. The objective is to incrementally wake up sleeping links upon the detection of increased traffic demand. Unlike normal approaches of manipulating link weights or reverting to full topology in case of even minor network congestion and thereby sacrificing energy savings, our algorithm wakes up the minimum number of sleeping links to the network in order to handle this dynamicity. The performance of our algorithm was evaluated using the GEANT network topology and its traffic traces over a period of one week. According to our simulation results, up to almost 47% energy gains can be achieved without any obstruction to the network performance. Secondly, we show that the activation of a small number of sleeping links is still sufficient to cope with the observed traffic surge. Document type: Part of book or chapter of book

Abstract

An important requirement of a robust traffic engineering solution is insensitivity to changes, be they in the form of traffic fluctuations or changes in the network topology because of link failures. In this paper we focus on developing a fast and effective technique to compute traffic engineering solutions for Interior Gateway Protocol (IGPs) environments that are robust to link failures in the logical topology. The routing and packet forwarding decisions for IGPs is primarily governed by link weights. Our focus is on computing a single set of link weights for a traffic engineering instance that performs well over all single logical link failures. Such types of failures, although usually not long lasting, of the order of tens of minutes, can occur with high enough frequency, of the order of several a day, to significantly affect network performance. The relatively short duration of such failures coupled with issues of computational complexity and convergence time due to the size of current day networks discourage adaptive reactions to such events. Consequently, it is desirable to a priori compute a routing solution that performs well in all such scenarios. Through computational evaluations we demonstrate that our technique yields link weights that perform well over all single link failures and also scales well, in terms of computational complexity, with the size of the network. Document type: Part of book or chapter of book

Abstract

In this work, the main goal is to develop and evaluate a number of optimization algorithms in the task of improving Quality of Service levels in TCP/IP based networks, by configuring the routing weights of link-state protocols such as OSPF. Since this is a complex problem, some meta-heuristics from the Evolutionary Computation arena were considered, working over a mathematical model that allows for flexible cost functions, taking into account several measures of the network behavior such as network congestion and end-to-end delays. A number of experiments were performed, resorting to a large set of network topologies, where Evolutionary Algorithms (EAs), Differential Evolution and some common heuristic methods including local search were compared. EAs make the most promising alternative leading to solutions with an effective network performance even under unfavorable scenarios. Document type: Part of book or chapter of book

Abstract

In this paper we present an intelligent multi-topology IGP (MT-IGP) based intra-domain traffic engineering (TE) scheme that is able to handle unexpected traffic fluctuations with near-optimal network performance. First of all, the network is dimensioned through offline link weight optimization using Multi-Topology IGPs for achieving maximum path diversity across multiple routing topologies. Based on this optimized MT-IGP configuration, an adaptive traffic engineering algorithm performs dynamic traffic splitting adjustment for balancing the load across multiple routing topologies in reaction to the monitored traffic dynamics. Such an approach is able to efficiently minimize the occurrence of network congestion without the necessity of frequently changing IGP link weights that may cause transient forwarding loops and routing instability. Our experiments based on real network topologies and traffic matrices show that our approach has a high chance of achieving near-optimal network performance with only a small number of routing topologies. Document type: Part of book or chapter of book

Abstract

The focus of the paper is an investigation and evaluation of energy efficient solutions in IP over WDM core networks using as a foundation, a hierarchy of hibernation modes implementing different degrees of node groupings and fibre links establishment that support a sleep state. It seeks to embed this groups-nodes strategy into an intelligent control plane implementing routing schemes targeting energy consumption, adaptive signalling and traffic engineering. A Group-Nodes mechanism is proposed as a function of topology and node distribution based on a fixed (or geographical) and random (or ownership) principle. The impact of the proposed technique on energy saving and network performance is assessed; results are presented and evaluated for various scenarios. Evaluation of this methodology indicates potential reduction in power consumption from 7 % up to 15 % at the expense of reduced network performance. Document type: Part of book or chapter of book

Abstract

Complex Systems are those in which a very large number of elements interact, usually in a non-linear fashion, producing emergent behaviors that are typically difficult to predict. Air transportation systems fall in this category, with a large number of aircraft following a pre-scheduled program. It has been shown that it is possible to understand and forecast delays propagation in these systems. The objective of this analysis is to compare the modeling in the US and in the European air traffic networks, analyzing the propagation of delays due to failures in the schedule or to disturbances. We use two different agent based models recently developed to simulate the delays propagation and assess the effect of disruptions in the networks (US and ECAC areas). Our results show that a first-come first-served protocol managing the flights produces larger congestion when compared with an ATFM (Air Traffic Flow Management) slots priority system. This work is co-financed by EUROCONTROL acting on behalf of the SESAR Joint Undertaking (the SJU) and the EUROPEAN UNION as part of TREE project under the Work Package E in the SESAR Programme. Bruno Campanelli is funded by the Conselleria d'Educació, Cultura i Universitats of the Government of the Balearic Islands and the European Social Fund. José J. Ramasco acknowledges funding from the Ramón y Cajal program of the Spanish Ministry of Economy (MINECO). Peer reviewed