Políticas de encaminamiento tolerantes a fallos

El uso intensivo y prolongado de computadores de altas prestaciones para ejecutar aplicaciones computacionalmente intensivas, sumado al elevado número de elementos que los componen, incrementan drásticamente la probabilidad de ocurrencia de fallos durante su funcionamiento. El objetivo del trabajo es resolver el problema de tolerancia a fallos para redes de interconexión de altas prestaciones, partiendo del diseño de polí­ticas de encaminamiento tolerantes a fallos. Buscamos resolver una determinada cantidad de fallos de enlaces y nodos, considerando sus factores de impacto y probabilidad de aparición. Para ello aprovechamos la redundancia de caminos de comunicación existentes, partiendo desde enfoques de encaminamiento adaptativos capaces de cumplir con las cuatro fases de la tolerancia a fallos: detección del error, contención del daño, recuperación del error, y tratamiento del fallo y continuidad del servicio. La experimentación muestra una degradación de prestaciones menor al 5%. En el futuro, se tratará la pérdida de información en tránsito.L'ús intensiu i perllongat de computadors d'altes prestacions per a executar aplicacions computacionalment intensives, sumat a l'elevat nombre d'elements que els componen, incrementen dràsticament la probabilitat d'ocurrència de fallades durant el seu funcionament. L'objectiu del treball és resoldre el problema de tolerància a fallades per a xarxes d'interconnexió d'altes prestacions, partint del disseny de polítiques d'encaminament tolerants a fallades. Busquem resoldre una determinada quantitat de fallades d'enllaços i nodes, considerant els seus factors d'impacte, probabilitat d'aparició. Per a això s'aprofita la redundància de camins de comunicació existents, partint des d'enfocaments d'encaminament adaptatius capaços de complir amb les quatre fases de la tolerància a fallades: detecció de l'error, contenció del dany, recuperació de l'error, i tractament de la fallada i continuïtat del servei. L'experimentació mostra una degradació de prestacions menor al 5%. En el futur, es tractarà la pèrdua d'informació en trànsit.The intensive and continous use of high-performance computers to execute computationally intensive applications, coupled with the large number of elements that make them up, dramatically increase the likelihood of failures during their operation. This works focuses on solving the problem of fault tolerance for high speed interconnection networks by means of designing fault tolerant routing policies. The goal is to solve a determined number of link and node failures, considering its impact factor and occurrence probability. To acomplish this task we take advantage of the communication path redundancy, through adaptive routing approaches that fulfils with the four phases of the fault tolerance: error detection, damage confinement and assessment, error recovery, fault treatment and continuous service. The experiments shows performanceâs degradation under 5%. In the future, weâll treat the loose of information in transit

Doctor of Philosophy

dissertationOver the last decade, cyber-physical systems (CPSs) have seen significant applications in many safety-critical areas, such as autonomous automotive systems, automatic pilot avionics, wireless sensor networks, etc. A Cps uses networked embedded computers to monitor and control physical processes. The motivating example for this dissertation is the use of fault- tolerant routing protocol for a Network-on-Chip (NoC) architecture that connects electronic control units (Ecus) to regulate sensors and actuators in a vehicle. With a network allowing Ecus to communicate with each other, it is possible for them to share processing power to improve performance. In addition, networked Ecus enable flexible mapping to physical processes (e.g., sensors, actuators), which increases resilience to Ecu failures by reassigning physical processes to spare Ecus. For the on-chip routing protocol, the ability to tolerate network faults is important for hardware reconfiguration to maintain the normal operation of a system. Adding a fault-tolerance feature in a routing protocol, however, increases its design complexity, making it prone to many functional problems. Formal verification techniques are therefore needed to verify its correctness. This dissertation proposes a link-fault-tolerant, multiflit wormhole routing algorithm, and its formal modeling and verification using two different methodologies. An improvement upon the previously published fault-tolerant routing algorithm, a link-fault routing algorithm is proposed to relax the unrealistic node-fault assumptions of these algorithms, while avoiding deadlock conservatively by appropriately dropping network packets. This routing algorithm, together with its routing architecture, is then modeled in a process-algebra language LNT, and compositional verification techniques are used to verify its key functional properties. As a comparison, it is modeled using channel-level VHDL which is compiled to labeled Petri-nets (LPNs). Algorithms for a partial order reduction method on LPNs are given. An optimal result is obtained from heuristics that trace back on LPNs to find causally related enabled predecessor transitions. Key observations are made from the comparison between these two verification methodologies