Optimizing IGP Link Costs for Improving IP-level Resilience

Recently, major vendors have introduced new router platforms to the market that support fast IP-level failure pro- tection out of the box. The implementations are based on the IP Fast ReRoute–Loop Free Alternates (LFA) standard. LFA is simple, unobtrusive, and easily deployable. This simplicity, however, comes at a severe price, in that LFA usually cannot protect all possible failure scenarios. In this paper, we give new graph theoretical tools for analyzing LFA failure case coverage and we seek ways for improvement. In particular, we investigate how to optimize IGP link costs to maximize the number of protected failure scenarios, we show that this problem is NP- complete even in a very restricted formulation, and we give exact and approximate algorithms to solve it. Our simulation studies show that a deliberate selection of IGP costs can bring many networks close to complete LFA-based protection

High Availability in the Future Internet

With the evolution of the Internet, a huge number of real- time applications, like Voice over IP, has started to use IP as primary transmission medium. These services require high availability, which is not amongst the main features of today’s heterogeneous Internet where fail- ures occur frequently. Unfortunately, the primary fast resilience scheme implemented in IP routers, Loop-Free Alternates (LFA), usually does not provide full protection against failures. Consequently, there has been a growing interest in LFA-based network optimization methods, aimed at tuning some aspect of the underlying IP topology to maximize the ratio of failure cases covered by LFA. The main goal of this chapter is to give a comprehensive overview of LFA and survey the related LFA network op- timization methods, pointing out that these optimization tools can turn LFA into an easy-to-deploy yet highly effective IP fast resilience scheme

Optimizing IGP link costs for improving IP-level resilience

The IP Fast ReRoute–Loop-Free Alternates (LFA) standard is a simple and easily deployable technique to provide fast failure protection right in the IP layer. To our days, most major IP device vendors have products on the market that support LFA out of the box. Unfortunately, LFA usually cannot protect all possible failure scenarios in a general network topology. Therefore, it is crucial to develop LFA-based network optimization tools in order to assist operators in deciding whether deploying LFA in their network will supply sufficient resiliency. In this paper, we give a new graph theoretical framework for analyzing LFA failure case coverage, and then we investigate how to optimize the Interior Gateway Protocol (IGP) link costs in order to maximize the number of protected failure scenarios. We show that this problem is NP-complete even in a very restricted formulation, and we give an exact algorithm as well as a complete family of heuristics to solve it. Our simulation studies indicate that a deliberate tuning of the approximation strategy can significantly improve the quality of the IGP link costs, and we conclude that LFA cost optimization has the potential for boosting LFAbased resilience in most operational networks significantly

Otimização de redes IP com mecanismos de reencaminhamento rápido

Mestrado em Engenharia de Computadores e TelemáticaThis dissertation studies strategies for assigning costs to the interfaces of routers inside an IP network to potentiate the use of Loop-Free Alternates (LFA). LFA is a fast reroute mechanism that has been recently deployed in commercial routers. This mechanism allows routers to forward traffic through alternative paths right after the detection of a network failure, avoiding a higher loss of packets during the network’s recovery process. The problem is that this mechanism does not usually provide coverage to all possible failures. Moreover, repair paths may lead to congestion and even forwarding loops. An application was developed that, given a network topology and its supporting traffic matrix, allows to find IGP costs that improve the network performance when employing this mechanism. The implemented strategies try to minimize situations where the use of repair paths leads to micro-loops or link overloads, thus preserving the quality of the service. The computational results show that it is possible to minimize the effects of a failure through an intelligent choice of costs. It is also possible to conclude that, for the majority of cases, increasing the LFA coverage of a network is not the best strategy. Depending on the available resources, it becomes often necessary to sacrifice this coverage to obtain better performance levels.Esta dissertação estuda estratégias para a atribuição de custos IGP às interfaces dos routers de uma rede IP de forma a potenciar o uso de Loop-Free Alternates (LFA), um mecanismo de reencaminhamento rápido que tem sido recentemente implementado em routers comerciais. Este mecanismo permite que os routers reencaminhem tráfego por rotas alternativas assim que uma falha de rede é detetada, evitando uma maior perda de pacotes durante o período de recuperação da rede. O problema é que este mecanismo geralmente não oferece cobertura para todas as falhas possíveis. Além disso, as rotas de restauro podem causar congestão na rede e até mesmo ciclos de encaminhamento. Foi então desenvolvida uma aplicação que, dada uma topologia de rede e respetiva matriz de tráfego, permite determinar custos que melhorem o desempenho da rede quando emprega este mecanismo. As estratégias implementadas procuram minimizar situações em que o uso das rotas de restauro provoca ciclos de encaminhamento ou sobrecarga das ligações, preservando desta forma a qualidade da maior parte do serviço. Os resultados obtidos mostram que é possível minimizar os efeitos de uma falha através de uma escolha inteligente dos custos. Também é possível concluir que, na grande maioria dos casos, aumentar de forma cega a cobertura da rede através de Loop-Free Alternates não é a melhor estratégia. Dependendo dos recursos disponíveis, torna-se muitas vezes necessário sacrificar essa cobertura para obter melhores níveis globais de desempenho

Smart Sensor Technologies for IoT

The recent development in wireless networks and devices has led to novel services that will utilize wireless communication on a new level. Much effort and resources have been dedicated to establishing new communication networks that will support machine-to-machine communication and the Internet of Things (IoT). In these systems, various smart and sensory devices are deployed and connected, enabling large amounts of data to be streamed. Smart services represent new trends in mobile services, i.e., a completely new spectrum of context-aware, personalized, and intelligent services and applications. A variety of existing services utilize information about the position of the user or mobile device. The position of mobile devices is often achieved using the Global Navigation Satellite System (GNSS) chips that are integrated into all modern mobile devices (smartphones). However, GNSS is not always a reliable source of position estimates due to multipath propagation and signal blockage. Moreover, integrating GNSS chips into all devices might have a negative impact on the battery life of future IoT applications. Therefore, alternative solutions to position estimation should be investigated and implemented in IoT applications. This Special Issue, “Smart Sensor Technologies for IoT” aims to report on some of the recent research efforts on this increasingly important topic. The twelve accepted papers in this issue cover various aspects of Smart Sensor Technologies for IoT