Fault-tolerant routing with regularity restoration in Boolean n-cube 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.

In this paper we propose a new algorithm for routing in mobile survivable networks, based on the combination of position-based routing concepts and fault-tolerant routing techniques in computer networks. By using a combination of these two concepts we achieve a simplified way of localizing routing overhead while at the same time we improve the operational effectiveness of the position-based routing approaches by alleviating some of the drawbacks associated with them, such as routing deadlock occurrences, and therefore creating a robust and fault tolerant routing strategy.

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.

Distributed connectivity restoration in multichannel wireless sensor networks

A large-scale sensor network (LSSN) is formed when a very large number of sensor nodes with short-range communication capabilities are deployed randomly over an extended region. The random distribution of nodes in an LSSN leads to regions of varying density, which means that if all nodes have an identical transmission radius, the effective connectivity would vary over the system. This leads to inefficiency in energy usage (in regions of unnecessarily high connectivity) and the danger of partitioning (in regions of low node density). In this paper, we propose a technique for adapting a node’s transmission radius based on a node’s local information. Through localized coordination and self-organization, nodes try to attain fairly uniform connectivity in the system to aid in efficient data messaging in the system. We study the benefits of network adaptation by incorporating it into an adaptive geographical routing algorithm called corridor routing. We present simulation results showing significant improvement in performance over routing algorithms that do not use network adaptation. We also propose and study several scenarios for network adaptation in the presence of node failures, and explore the effect of parameter variation.

Server-centric data center architecture has been proposed to provide high throughput, scalable construction and error tolerance with commodity servers and switches for cloud data centers. To fully utilize those advantages of server-centric data center, an effective routing algorithm to find high quality multiple paths in Server-centric network is needed. However, current routing algorithms cannot achieve this completely: (1) the state-of-art routing algorithms in server-centric data center just consider hop count when selecting paths; (2) traditional multi-constraint QoS routing algorithms only find one feasible path and are usually switch-oriented; (3) present multi-path algorithms cannot guarantee the performance of the founded paths. In this paper, we propose a multi-constrained routing algorithm for server-centric data centers, named Server-Centric Multi-Constrained Routing Algorithm (SCRAT). This algorithm exploits the topology features of the Server-Centric data center to decrease the algorithm complexity and returns optimal and feasible paths simultaneously. In simulations, SCRAT has a very high probability (more than 96 %) to find the exact optimal path, and the cost of the optimal path found in SCRAT is about 10 % less compared with path found in previous TS_MCOP. Compared with previous MPTCP, SCRAT reduces the path delay by 18 % less and increase the bandwidth by 20 %.KeywordsTraditional Data Center NetworksServer-centric NetworkFeasible PathOriginal Routing AlgorithmOptimal PathThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Recently, the merits of cooperative communication in the physical layer have been explored. However, the impact of cooperative communication on the design of the higher layers has not been well-understood yet. Cooperative routing in wireless networks has gained much interest due to its ability to exploit the broadcast nature of the wireless medium in designing power efficient routing algorithms. Most of the existing cooperation based routing algorithms are implemented by finding a shortest path route first and then improving the route using cooperative communication. As such, these routing algorithms do not fully exploit the merits of cooperative communications, since the optimal cooperative route might not be similar to the shortest path route. In this paper, we propose a cooperation-based routing algorithm, namely, the minimum power cooperative routing (MPCR) algorithm, which makes full use of the cooperative communications while constructing the minimum-power route. The MPCR algorithm constructs the minimum-power route, which guarantees certain throughput, as a cascade of the minimum-power single-relay building blocks from the source to the destination. Thus, any distributed shortest path algorithm can be utilized to find the optimal cooperative route with polynomial complexity. Using analysis, we show that the MPCR algorithm can achieve power saving of 65.61% in regular linear networks and 29.8% in regular grid networks compared to the existing cooperation-based routing algorithms, where the cooperative routes are constructed based on the shortest-path routes. From simulation results, MPCR algorithm can have 37.64% power saving in random networks compared to those cooperation-based routing algorithms.

This paper presents a deadlock-free fault-tolerant routing algorithm for irregular mesh network-on-chips based on a region-based approach. In this approach, a set of rectangular faulty regions called faulty blocks is formed for faulty nodes and a detour path is defined for each faulty block to indicate how packets must detour thefaulty block. The most recent routing algorithm on this approach is Message-Route (Holsmark and Kumar J Inf Sci Eng 23:1649---1662, 2007) which does not have restrictions on the number of tolerable faulty nodes and its distribution. However, this algorithm has three crucial problems; (1) this algorithm fails to provide complete and deadlock-free routing, (2) many nonfaulty nodes are contained in faulty blocks and thus deactivated, and (3) complex routing functions are not feasible for hardware implementation. In this paper, we give a solution for each of the above three problems. We correct the errors of Message-Route to make it complete and deadlock-free. Then, we propose a deadlock-free fault-tolerant routing algorithm which can work under small-sized faulty blocks with a simple routing control. Experimental results show that the proposed algorithm significantly reduces the size of faulty blocks and improves communication latency for both random and cluster faults. Moreover, an FPGA implementation of the proposed algorithm is also discussed.

A network based on the hypercube, called the multiply twisted cube is proposed. This network preserves many of the desirable properties of the hypercube, but has a diameter which is only ((n+1)/2) for an n-dimensional multiple twisted cube, a reduction of nearly 50% compared to the ordinary hypercube. Some of the basic topological properties of multiply twisted cubes are discussed, and a routing algorithm which produces optimal paths is presented. This network is self-routing, in the sense that there is a simple distributed routing algorithm which guarantees optimal paths between any pair of vertices. This fact, together with other properties such as regularity, symmetry, high connectivity, and a simple recursive structure, suggests that the multiply twisted cube is an attractive alternative to the ordinary hypercube for massively parallel architectures. >

Fault-tolerance has been the focus of attention recently in the research of parallel processing and computer networking. A fault-tolerant routing algorithm should guarantee the delivery of messages in the presence of faulty components. In this paper, we present a comparative performance study of seven prominent fault-tolerant routings in 2-D wormhole-switched tori. The routing algorithms here are coupled with the Software-Based routing scheme which supports dynamic fault-model, enabling the network to remain fully operational at all times. The performance measures studied here are the throughput and average message latency. Results obtained through simulation suggest two classes of presented routing schemes as high performance candidates in most faulty networks.

In this paper, a novel fault-tolerant source routing algorithm for Network on Chip (NOC) called Stochastic Prefix-based Source Routing (SPSR) is proposed. Compared to non-source routing algorithms, it releases the intermediate node from complicated decision-making or routing table maintenance. Unlike the traditional source routing algorithms which use broadcast packets to record the YD of every intermediate node in Route Discovery, it predetermine prospective routes, which can greatly reduces the packets generated and forwarded in the Route Discovery phase, and therefore reduces the power consumption. The proposed routing algorithm is implemented on the open source simulator Nirgam [14], incorporating Orion [15] to estimate the power consumption. Experiment results show that the proposed algorithm can greatly reduce the power consumption in the route discovery and the latency of SPSR is comparable with that of the broadcasting mechanism.

The hierarchical routing and wavelength assignment problem in Automatic Switched Optical Network (ASON) is researched. Based on our analysis, three adaptive algorithms called MLLR (Multi-Layer Least Loaded Routing Algorithm), WMLCR (Wavelength-graph-based Multi-Layer Least Congestion Routing Algorithm) and BMR (Backtracking-based Multi-Layer Routing Algorithm) are proposed. A platform named AHORSP (ASON based hierarchical optimal routing & signaling platform) supporting our routing scheme is proposed and demonstrated. The simulation shows that the proposed algorithms can have comprehensive application on the basis of their convenience to be realized, low BP performance and acceptable operation time.

Fault-tolerant routing is the ability to survive beyond the failure of individual components and usually uses several virtual channels (VCs) to pass faulty nodes or links. A well-known wormhole-switched routing algorithm for 2-D mesh interconnection network, f-cube3, uses three virtual channels to pass faulty blocks such as f-ring and f-chain, while only one virtual channel is used when a message does not encounter any fault. One of the key issues in the design of NoCs is the development of an efficient communication system to provide high throughput and low latency interconnection networks. We have evaluated a new fault-tolerant routing algorithm based on f-cube3 as a solution to increase the throughput of physical links more than f-cube3 with lower message delay which uses less number of VCs compared to f-cube3 by reducing required virtual channels to two. Simulation of both f-cube3 and improved algorithm, if-cube2 (improved f-cube2) for the same conditions presented. As the simulation results show, if-cube2 has a higher performance than f-cube3 algorithm even with one less VC. The results also show that our algorithm has less exist packets in network and better performance with 100% traffic load in Network-on-Chip.KeywordsNetwork-on-Chipthroughputperformanceinterconnectionfault-tolerant routingwormhole switchingvirtual channeldeterministic routing

In this paper, we would present a fault-tolerant wormhole routing scheme, called two-level-turn-model scheme, in the tori with convex faults. The reason why we choose the convex faults is that the shape of the convex faults is instrumental to design an effective fault-tolerant routing algorithm. Compared with many other solutions, which mainly focus on providing extra virtual channels to tolerate the faults, one of the advantages of our solution is that it is based on the turn model, which itself could tolerate some faults for some messages. At the same time, our solution could work effectively no matter where the fault region locates and no matter whether the fault regions are connected. In our solution, two patterns of the turn model are complementary to tolerate the faults. With a few limits to the shape of the convex faults, at most five virtual channels per physical channel are required to avoid the deadlock.

Network-on-Chip (NoC) is evolving as an efficient and scalable interconnect architecture for current and future CMP, MPSoC systems. An important challenge in NoC design is to choose an appropriate routing algorithm, as it impacts the NoC performance. As technology scales down to Deep-Submicron (DSM), on-chip networks are becoming increasingly prone to failures. At higher level these failures are handled by fault tolerant routing algorithms. Fault tolerant routing algorithms avoid faulty regions and route traffic through safe regions. Currently, routing algorithms are implemented as source or distributed routing. To handle faults, both source and distributed routing make use of routing tables. Algorithms implemented with routing tables do not scale well with network size. Scalable routing implementation, such as Logic Based Distributed Routing (LBDR) has been proposed for efficient and compact implementation of routing. LBDR handles faults without using routing table. In this paper we propose a fault tolerant routing scheme based on LBDR which aims to handle faults while at the same time addressing network congestion. Proposed method integrates deterministic and adaptive routing schemes to avoid congestion as well as faults that may be present in the network. Experimental results show the effectiveness of proposed method in case of single and multiple link failures.