Networks-on-chip need to survive to manufacturing faults in order to sustain yield. An effective testing and configuration strategy however implies two opposite requirements. One one hand, a fast and scalable built-in self-testing and self-diagnosis procedure has to be carried out concurrently at NoC switches. On the other hand, programming the NoC routing mechanism to go around faulty links and switches can be optimally performed by a centralized controller with global network visibility. To the best of our knowledge, this article proposes for the first time a global network testing and configuration strategy that meets the opposite requirements by means of a fault-tolerant dual network architecture and a fast configuration algorithm for the most common failure patterns. Experimental results report an area overhead as low as 12.5% with respect to the baseline switch architecture while achieving a high degree of fault tolerance. In fact, even when multiple stuck-at faults are considered, the capability of fault masking by the dual network is always over 80%, and the support for multiple link failures is more than 90% in presence of two unusable links in the main network with minimum set-up times.
Abstract. Current interconnect standards providing hardware support for quality of service (QoS) consider up to 16 virtual channels (VCs) for this purpose. However, most implementations do not offer so many VCs because they increase the complexity of the switch and the scheduling delays. In this paper, we show that this number of VCs can be significantly reduced. Some of the scheduling decisions made at network interfaces can be easily reused at switches without significantly altering the global behavior. Specifically, we show that it is enough to use two VCs for QoS purposes at each switch port, thereby simplifying the design and reducing its cost.
Abstract-The InfiniBand Architecture (IBA) has been proposed as an industry standard both for communication between processing nodes and I/O devices and for interprocessor communication. It replaces the traditional bus-based interconnect with a switch-based network for connecting processing nodes and I/O devices. It is being developed by the InfiniBand SM Trade Association (IBTA) in the aim to provide the levels of reliability, availability, performance, scalability, and quality of service (QoS) required by present and future server systems. For this purpose, IBA provides a series of mechanisms that are able to guarantee QoS to the applications. In previous papers, we have proposed a strategy to compute the InfiniBand arbitration tables. In one of these, we presented and evaluated our proposal to treat traffic with bandwidth requirements. In another, we evaluated our strategy to compute the InfiniBand arbitration tables for traffic with delay requirements, which is a more complex task. In this paper, we will evaluate both these proposals together. Furthermore, we will also adapt these proposals in order to treat VBR traffic without QoS guarantees, but achieving very good results. Performance results show that, with a correct treatment of each traffic class in the arbitration of the output port, all traffic classes reach their QoS requirements.
High-speed local area networks (LANs) consist of a set of switches connected by point-to-point links, and hostslinked to switches through a network interface card. Highspeed LANs may change their topology due to switches and hosts being turned on/off, link remapping, and component failures. In these cases, a distributed reconfiguration algorithm analyzes the topology, computes the new routing tables, and downloads them to the corresponding switches. Unfortunately, in most cases, user traffic is stopped during the reconfiguration process to avoid deadlock. Although network reconfigurations are not frequent, static reconfiguration such as this may take hundreds of milliseconds to execute, thus degrading system availability significantly.Several distributed real-time applications have strict communication requirements [9,11]. Distributed multimedia applications have similar, although less strict, quality of service (QoS) requirements. Both stopping packet transmission and discarding packets due to the reconfiguration process prevent the system from satisfying the above requirements. Therefore, in order to support hard real-time and distributed multimedia applications over a high-speed LAN, we need to avoid stopping user traffic and discarding packets when the topology changes.In this paper, we propose a new deadlock-free distributed reconfiguration algorithm that is able to asynchronously update routing tables without stopping user traffic. This algorithm is valid for any topology, including regular as well as irregular topologies. Simulation results show that the behavior of our algorithm is significantly better than for other algorithms based on a spanning-tree formation.
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