A Region-based Fault-Tolerant Routing Algorithmfor 2D Irregular Mesh Network-on-Chip

We propose a deterministic fault-tolerant and deadlock-free routing protocol in 2-dimensional (2-D) meshes based on dimension-order routing and the recently proposed odd-even turn model. The proposed protocol, called extended X-Y routing, does not use any virtual channels by prohibiting certain locations of faults and destinations. Faults are contained in a set of disjointed rectangular regions called faulty blocks. The number of faults to be tolerated is unbounded as long as nodes outside faulty blocks are connected in the mesh network. The extended X-Y routing can also be used under a special convex fault region called orthogonal faulty block, which can be derived from a given faulty block by activating some nonfaulty nodes in the block. Extensions to partial adaptive routing, traffic- and adaptivity-balanced using virtual networks, and routing without constraints using virtual channels and virtual networks are also discussed.

Fault-tolerant routing is usually used to provide reliable on-chip communication for many-core processors. This paper focuses on a special class of algorithms that do not use virtual channels. One of the major challenges is to keep the network deadlock free in the presence of faults, especially those locating on network edges. State-of-the-art solutions address this problem by either disabling all nodes of the faulty network edges or including all faults into one faulty block. Therefore, a large number of fault-free nodes will be sacrificed. To address this problem, the proposed ZoneDefense routing not only includes faults into convex faulty blocks but also spreads the faulty blocks' position information in corresponding columns. The nodes, which know the position of faulty blocks, form the defense zones. Therefore, packets can find the faulty blocks and route around them in advance. Exploiting the defense zones, the proposed ZoneDefense routing could tolerate many more faults with significantly reduced sacrificed fault-free nodes compared with the state-of-the-art algorithms. Furthermore, the ZoneDefense routing does not degrade the network performance in the absence of faults, and could get similar performance as its counterparts in the presence of faults.

The minimal routing problem in mesh-connected multicomputers with faulty blocks is studied. Two dimensional (2D) meshes are used to illustrate the approach. A sufficient condition for minimal routing in 2D meshes with faulty blocks is proposed. Unlike many other models that assume all the nodes know global fault distribution, our approach is based on the concept of an extended safety level which is a special form of limited fault information. Fault information is distributed to a limited number of nodes while it is still sufficient to support minimal routing. We study the existence of minimal paths at a given source node, limited distribution of fault information, and minimal routing itself. The proposed approach is also adaptive which allows all messages to use any minimal path. Our approach is the first attempt to address adaptive and minimal routing in 2D meshes with faulty blocks using limited fault information.

Fault-tolerant Manhattan routing algorithms aim at finding a Manhattan path between the source and destination nodes and route around all faulty nodes. However, besides faulty nodes, some nonfaulty nodes that are helpless to make up a fault-tolerant Manhattan path should also be routed around. How to label such nonfaulty nodes efficiently is a major challenge. We propose a path-counter method. It can label such nodes with low time-complexity by counting every node’s fault-tolerant Manhattan paths to the source or destination node. During the path-counting procedure, no available nodes will be sacrificed under arbitrary fault distribution. Compared with fault-block model based work, our proposed method is independent of fault distribution, so its computational complexity is very low.

A fault-tolerant routing algorithm for torus networks that uses only three virtual channels is presented. The proposed algorithm is based on the block fault model, which is suitable for modelling faults at the board level in networks with grid structures. Messages are routed via shortest paths when there are no faults. However, if a message is blocked by a faulty block, the message will use a detour path to route around the faulty block. Previously at least six virtual channels were needed to achieve the same fault-tolerant ability. Simulation results using various workloads and fault patterns are presented.

We obtain the conditional fault diameter of the k-ary n-cube interconnection network. It has been previously shown that under the condition of forbidden faulty sets (i.e. assuming each non-faulty node has at least one non-faulty neighbor), the k-ary n-cube, whose connectivity is 2n, can tolerate up to 4n-3 faulty nodes without becoming disconnected. We extend this result by showing that the conditional fault-diameter of the k-ary n-cube is equal to the fault-free diameter plus two. This means that if there are at most 4n-3 faulty nodes in the k-ary n-cube and if every non-faulty node has at least one non-faulty neighbor, then there exists a fault-free path of length at most the diameter plus two between any two non faulty nodes. We also show how to construct these fault-free paths. With this result the k-ary n-cube joins a group of interconnection networks (including the hypercube and the star-graph) whose conditional fault diameter has been shown to be only two units over the fault-free diameter.

We present a method to enhance wormhole routing algorithms for deadlock-free fault-tolerant routing in tori. We consider arbitrarily-located faulty blocks and assume only local knowledge of faults. Messages are routed via shortest paths when there are no faults, and this constraint is only slightly relaxed to facilitate routing in the presence of faults. The key concept we use is that, for each fault region, a fault ring consisting of fault free nodes and physical channels can be formed around it. These fault rings can be used to route messages around fault regions. We prove that at most four additional virtual channels are sufficient to make any fully-adaptive algorithm tolerant to multiple faulty blocks in torus networks. As an example of this technique, we present simulation results for a fully-adaptive algorithm and show that good performance can be obtained with as many as 10% links faulty.

A new performance measure for characterizing fault rings in interconnection networks

Compressionless Routing (GR) is a new adaptive routing framework which provides a unified framework for efficient deadlock-free adaptive routing and fault-tolerance. CR exploits the tight-coupling between wormhole routers for flow control to detect potential deadlock situations and recover from them. Fault-tolerant Compressionless Routing (FCR) extends Compressionless Routing to support end-to-end fault-tolerant delivery. Detailed routing algorithms, implementation complexity and performance simulation results for CR and FCR are presented.CR has the following advantages: deadlock-free adaptive routing in torus networks with no virtual channels, simple router designs, order-preserving message transmission, applicability to a wide variety of network topologies, and elimination of the need for buffer allocation messages. FCR has the following advantages: tolerates transient faults while maintaining data integrity (nonstop fault-tolerance), tolerates permanent faults, can be applied to a wide variety of network topologies, and eliminates the need for software buffering and retry for reliability. These advantages of CR and FCR not only simplify hardware support for adaptive routing and fault-tolerance, they also can simplify communication software layers.

Reconfiguration of Rings and Meshes in Faulty Hypercubes

Hole detection and shape-free representation and double landmarks based geographic routing in wireless sensor networks

We address the problem of reaching resilient consensus among a set of agents in the presence of faulty nodes (attacked or noisy). We propose general algorithms, i.e., receiving as inputs a consensus algorithm, the network topology, the initial states, and the number of maximum allowed faulty nodes. These algorithms let the agents identify the set of attacked nodes and correct the consensus value by ignoring the faulty nodes. We prove that if the number of faulty nodes is below the maximum allowed, then each non-faulty agent detects them without false positives. If the inputted discrete-time consensus algorithm has polynomial-time complexity , then the proposed correction algorithms have polynomial-time complexity (and for the detection of faulty nodes), for n nodes, and f maximum allowed faulty nodes. Finally, we show the effectiveness of the algorithms through simulation, pointing out attacking scenarios dealt with our methods, where the state-of-the-art underperformed.

An efficient diagnosis is very important for a multiprocessor system. In this paper, we present a \((\alpha ,\beta )\)-trees combination \(S(u,X,\alpha ,\beta )\) and give some conclusions about the local diagnosis. Based on the \((\alpha ,\beta )\)-trees combination, we give a conditional fault local diagnosis algorithm to identify the fault or fault-free status of each processor correctly under the MM\(^*\) model when the number of faulty nodes does not exceed \(\alpha +2\beta -3\) and every node has at least one fault-free neighboring node. According to our results, a connected network with a \((\alpha ,\beta )\)-trees combination \(S(u,X,\alpha ,\beta )\) for a node u is conditionally locally \((\alpha +2\beta -3)\)-diagnosable at node u and the time complexity of our algorithm to diagnose u is \(O(\alpha ^2\beta +\alpha \beta ^2)\). As an application, we show that our algorithm can identify all the faulty nodes of n-dimensional star graph \(S_n\) if the faulty node number does not exceed \(3n-8\). Compared with existing algorithms, our algorithm allows more faulty node in a multiprocessor system.KeywordsComparison diagnosis modelConditional diagnosisLocal diagnosabilityDiagnosis algorithm

Internet of Things (IoT) invoke to linkage of individually identifiable embedded devices within the current internet infrastructure. Wireless Sensor Network (WSN) is a network containing self-ruling sensors, which monitors environmental conditions. Interconnection of these sensors into IoT will be a big revolution in growing sensor technology. The increase in the number of sensor nodes, increases the number of faulty nodes. This affects the Quality of Service (QoS) of WSN based IoT. Efficient detection and reuse of faulty nodes enhances the quality of monitoring to a large extend. Due to the difficulty in indentifying the internal status of sensor nodes, it is important to develop algorithms to find faulty nodes. The conventional fault detection algorithms face low detection accuracy. In this work, three input fuzzy inference system (FIS) is used, which identifies hardware faults like, transmitter circuit condition, receiver circuit condition and battery condition. The simulation results show that the proposed scheme increases the detection accuracy when compared to the conventional schemes.

Network on chip (NoC) has been proposed as a solution for addressing the design challenges of future high performance nanoscale architectures. In NoCs, the traditional routing schemes are routing packets through a single path or multiple paths from one source node to a destination node, minimizing the congestion in the routing architecture. Although these routing algorithms are moderately efficient, they are time dependent. To reduce overall data packet transmission time in the network, the authors consider a network with multiple sources and multiple destinations. Multi-dimensional routing problems appear naturally in several resource allocation problems, communication networks and wireless sensor networks. In this paper, the authors have constructed a deadlock-free multi-dimensional path routing algorithm for minimizing the congestion in NoC.