Adaptive Fault-tolerant Routing Algorithm Research Articles

A Network Adaptive Fault-Tolerant Routing Algorithm for Demanding Latency and Throughput Applications of Network-on-a-Chip Designs

Scalability is a significant issue in system-on-a-chip architectures because of the rapid increase in numerous on-chip resources. Moreover, hybrid processing elements demand diverse communication requirements, which system-on-a-chip architectures are unable to handle gracefully. Network-on-a-chip architectures have been proposed to address the scalability, contention, reusability, and congestion-related problems of current system-on-a-chip architectures. The reliability appears to be a challenging aspect of network-on-a-chip architectures because of the physical faults introduced in post-manufacturing processes. Therefore, to overcome such failures in network-on-a-chip architectures, fault-tolerant routing is critical. In this article, a network adaptive fault-tolerant routing algorithm is proposed, where the proposed algorithm enhances an efficient dynamic and adaptive routing algorithm. The proposed algorithm avoids livelocks because of its ability to select an alternate outport. It also manages to bypass congested regions of the network and balances the traffic load between outports that have an equal number of hop counts to its destination. Simulation results verified that in a fault-free scenario, the proposed solution outperformed a fault-tolerant XY by achieving a lower latency. At the same time, it attained a higher flit delivery ratio compared to the efficient dynamic and adaptive routing algorithm. Meanwhile, in the situation of a faulty network, the proposed algorithm could reach a higher flit delivery ratio of up to 18% while still consuming less power compared to the efficient dynamic and adaptive routing algorithm.

Fault-Tolerant Adaptive Routing in Dragonfly Networks

Dragonfly networks have been widely used in the current high-performance computers or high-end servers. Fault-tolerant routing in dragonfly networks is essential. The rich interconnects provide good fault-tolerance ability for the network. A new deadlock-free adaptive fault-tolerant routing algorithm based on a new two-layer safety information model, is proposed by mapping routers in a group, and groups of the dragonfly network into two separate hypercubes. The new fault-tolerant routing algorithm tolerates static and dynamic faults. Our method can determine whether a packet can reach the destination at the source by using the new safety information model, which avoids dead-ends and aimless misrouting. Sufficient simulation results show that the proposed fault-tolerant routing algorithm even outperforms the previous minimal routing algorithm in fault-free networks in many cases.

Efficient Design-for-Test Approach for Networks-on-Chip

To achieve high reliability in on-chip networks, it is necessary to test the network continuously with Built-in Self-Tests (BIST) so that the faults can be detected quickly and the number of affected packets can be minimized. However, BIST causes significant performance loss due to data dependencies. We propose EsyTest, a comprehensive test strategy with minimized influence on system performance. EsyTest tests the data path and the control path separately. The data path test starts periodically, but the actual test performs in the free time slots to avoid deactivating the router for testing. A reconfigurable router architecture and an adaptive fault-tolerant routing algorithm are proposed to guarantee the access to the processing core when the associated router is under test. During the whole test procedure of the network, all processing cores are accessible, and thus the system performance is maintained during the test. At the same time, EsyTest provides a full test coverage for the NoC and a better hardware compatibility comparing with the existing test strategies. Under the PARSEC benchmark and different test frequencies, the execution time increases less than 5 percent at the cost of 9.9 percent more area and 4.6 percent more power in comparison with the execution where no test procedure is applied.

Dynamic Fault-Tolerant Routing Based on FSA for LEO Satellite Networks

We formalize the construction of fault blocks by a state transition model based on finite state automata. Based on the model, a boundary diffusion method is presented for the rectilinear-monotone orthogonal convex fault model such as the rectangular fault model and minimal-connected-component (MCC) faulty model, whereby an adaptive fault-tolerant routing algorithm, called X-Y boundary routing algorithm (X-YBRA), is presented for deadlock-free fault-tolerant adaptive routing outside the fault blocks. To improve the network resources utilization, we put forward a routing diffusion method in the fault block, which completely solves the routing problem in the fault block. The experiment result shows that the diffusion overhead of our method is far lower than that of the traditional routing algorithms such as distance vector and link state routing algorithms with the light loss in convergence time. For the occurrence and recovery of random faults, the expansion and shrinkage of the fault block are also discussed. Accordingly, the dynamic boundary and routing updating methods are put forward to respond to these cases. Based on these methods, we develop low earth orbit satellite networks into an adaptive fault-tolerant system in routing. Our works can be also applied to other 2D mesh networks such as the interconnect multiprocessor computer systems.

Performance analysis of minimal path fault tolerant routing in NoC

Occurrence of faults in Network on Chip (NoC) is inevitable as the feature size is con- tinuously decreasing and processing elements are increasing in numbers. Faults can be revocable if it is transient. Transient fault may occur inside router, or in the core or in communication wires. Examples of transient faults are overflow of buffers in router, clock skew, cross talk, etc.. Revocation of transient faults can be done by retransmission of faulty packets using oblivious or adaptive routing algorithms. Irrevocable faults causes non-functionality of segment and mainly occurs during fabrication process. NoC reliability increases with the efficient routing algorithms, which can handle the maximum faults without deadlock in network. As transient faults are temporary and can be easily revoked using re- transmission of packet, permanent faults require efficient routing to route the packet by bypassing the nonfunctional segments. Thus, our focus is on the analysis of adaptive minimal path fault tolerant routing to handle the permanent faults. Comparative analysis between partial adaptive fault tolerance routing West-First, North-Last, Negative-First, Odd Even, and Minimal path Fault Tolerant routing (MinFT) algorithms with the nodes and links failure is performed using NoC Interconnect RoutinG and Application Modeling simulator (NIRGAM) for the 2D Mesh topology. Result suggests that MinFT ensures data transmission under worst conditions as compared to other adaptive routing algorithms .

A new performance measure for characterizing fault rings in interconnection networks

One of the fundamental issues in parallel computers is how to efficiently perform routing in a faulty network where each component fails with some probability. Adaptive fault-tolerant routing algorithms in such systems have been frequently suggested as a means of providing continuous operations in the presence of one or more failures by allowing the graceful system degradation. Many algorithms involve adding buffer space and complex control logic to the routing nodes. However, the addition of extra logic circuits and buffer space makes nodes more liable to failure and less reliable. Further, if the shape of fault pattern is confined, then many non-faulty nodes will be sacrificed and hence their resources are wasted. This is clearly an undesirable solution and motivates solutions that provoke efficient use of non-faulty nodes. One such approach to reducing the number of functional nodes that must be marked as faulty is based on the concept of fault rings to support more flexible routing around rectangular fault regions. Before such schemes can be successfully incorporated in networks, it is necessary to have a clear understanding of the factors that affect their performance potential. In this paper, we propose the first general solution for computing the probability of message facing the fault rings with and without overlapping in the well-known torus networks. We also conduct extensive simulation experiments using various fault patterns, the results of which are used to confirm the good accuracy of the proposed analytical models.

Adaptive Fault Tolerant Routing Algorithm for Tree-Hypercube Multicomputer

A Connected tree-hypercube with faulty links and/or nodes is called injured tree-hypercube. To enable any non faulty node to communicate with any other non faulty node in an injured tree- hypercube, the information on component failures has to be made available to non faulty nodes to route message around the faulty components. We proposed an adaptive fault tolerant routing algorithm for an injured tree-hypercube in which requires each node to know only the condition of it's own links. This routing algorithm is shown to be capable of routing messages successfully in an injured tree- hypercube as long as the number of faulty components links and/or nodes is equal d (depth).

Wormhole routing for torus networks with faults

We present adaptive fault-tolerant routing algorithms for torus networks with wormhole routing. Messages are routed via shortest paths when there are no faults. However, if a message is blocked by faulty nodes or links, the message will find a detour path to route around the faulty nodes or links. Our model handles solid faults, which includes rectangular faults and many practical non-convex faults. Simulation results using various workloads and fault patterns are also given in this paper.

A Heuristic-Based Wormhole Routing Algorithm for Hypercube Multicomputer Networks

In this paper, we consider fault-tolerant routing algorithms in hypercube multicomputer networks. In particular, one of the most quoted adaptive fault-tolerant routing algorithm for hypercubes in the literature is studied in detail and its limited ability to route messages in the presence of some fault patterns (i.e., combination of node and link faults), is pointed out. A modified algorithm is proposed and its performance, using simulation, is compared to that of the above mentioned algorithm. It is shown that the proposed algorithm outperforms the existing one in terms of its ability to route routable messages around the hypercube in the presence of node and/or links faults. This improvement is achieved while using the same average path length or even improving it. Illustrative examples are shown in support of such improvement.

AN ADAPTIVE FAULT-TOLERANT WORMHOLE ROUTING ALGORITHM FOR HYPERCUBES

In this paper, we present an adaptive fault-tolerant wormhole routing algorithm for hypercubes by using 4 virtual networks. Each node is identified to be in one of the four states: safe, ordinarily unsafe, strongly unsafe, and faulty. Based on the concept of unsafe nodes, we design a routing algorithm for hypercubes that can tolerate at least n-1 faulty nodes and can route a message via a path of length no more than the Hamming distance between the source and destination plus four. Previous algorithms which achieve the same fault tolerant ability need at least 5 virtual channels per physical channel. Simulation results show that our algorithm outperforms previous known results.

Fault-tolerant wormhole routing in two-dimensional mesh networks with convex faults

Faulty blocks are expanded, by disabling nodes, to form rectangular faults in many existing works to facilitate the designing of deadlock-free routing schemes for meshes recently. In this paper, faulty blocks are diffused to be rectangular faults, which are composed of faulty and fault-diffused nodes. These rectangular faults are then shrunk, by recovering fault-diffused nodes, to form convex faults for reducing the number of nodes disabled. Simulation results show that up to 70% of the disabled nodes, which are needed to form rectangular faults, can be recovered if the number of faulty nodes is less than 10% of the total network nodes. Both non-adaptive and adaptive fault-tolerant routing algorithms are proposed to handle these resulted convex faults. The adaptive routing algorithm is enhanced from the non-adaptive counterpart by utilizing the virtual channels that are not used in the non-adaptive algorithm; hence, the number of virtual channels per physical channel used in the adaptive algorithm is the same to that used in the non-adaptive algorithm.

An adaptive fault-tolerant routing algorithm for hypercube multicomputers

This paper presents a partially adaptive fault-tolerant routing algorithm for hypercube multicomputers. The algorithm is tolerant to n-1 link and/or node faults for an n-cube. It makes routing decisions adaptively based on local failure information only. It is simple to implement and needs a very small message overhead. A comparison between the algorithm and a popular previous work is given.

A general framework for developing adaptive fault-tolerant routing algorithms

It is shown that Cartesian product (CP) graph-based network methods provide a useful framework for the design of reliable parallel computer systems. Given component networks with prespecified connectivity, more complex networks with known connectivity and terminal reliability can be developed. CP networks provide systematic techniques for developing reliable fault-tolerant routing schemes, even for very complex topological structures. The authors establish the theoretical foundations that relate the connectivity of a CP network, the connectivity of the component networks, and the number of faulty components: present an adaptive generic algorithm that can perform successful point-to-point routing in the presence of faults: synthesize, using the theoretical results, this adaptive fault-tolerant algorithm from algorithms written for the component networks: prove the correctness of the algorithm: and show that the algorithm ensures following an optimal path, in the presence of many faults, with high probability. >