LASH-TOR: a generic transition-oriented routing algorithm

An efficient all-to-all communication algorithm for torus and mesh networks, A2AT, was proposed. A2AT schedules message sending sequence so that all links are fully used by exploiting function of concurrent message transfer in the node. By using A2AT, the hop count of messages equals the maximum number of messages sharing a link in their routes for all message transfers. A2AT can therefore maintain synchronization without the need for phasing operation such as an MPI barrier. When the VOQ which is an ideal configuration for A2AT was used, communication times for mesh/torus network obtained by A2AT were roughly 1.20 and 1.09 times higher, on average, than those of the ideal times. When the networks had the minimum number of virtual channels and a small buffer, assuming a practical network, A2AT was able to reduce communication times by 12.5% and 36.0% compared with those of the conventional algorithm. When two controllers are used, A2AT reduced 28.2% and 55.7% communication time with those by A2AND on 15x15x15 (=3,375 nodes) mesh and torus networks respectively (18.6% and 44.8% in average). A2AT also reduced 15.1% and 41.9% of communication time with those by A2AND on the same mesh and torus networks respectively (14.4% and 37.5% in average) when six controllers are used.

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.

A Hierarchical Torus Network (HTN) is a 2D-torus network of multiple basic modules, in which the basic modules are 3D-torus networks that are hierarchically interconnected for higher level networks. The dynamic communication performance of the HTN using the dimension-order routing under common traffic patterns have been evaluated, and have been shown to be good. However, dynamic communication performance of HTN under adverse traffic patterns has not been evaluated yet. In this paper, we evaluate the dynamic communication performance of HTN using a deadlock-free dimension order routing with 3 virtual channels under adverse traffic patterns, and compare it with H3D-mesh, mesh, and torus networks. It is shown that even under adverse traffic patterns, the HTN yields high throughput and low average transfer time, which provide better dynamic communication performance than H3D-mesh, mesh, and torus networks.

ROMM is a class of Randomized, Oblivious, Multi--phase, Minimal routing algorithms. ROMM routing offers a potential for improved performance compared to both fully randomized algorithms and deterministic oblivious algorithms, under both light and heavy loads. ROMM routing also offers close to best case performance for many common routing problems. In previous work, these claims were supported by extensive simulations on binary cube networks [30, 31]. Here we present analytical and empirical results for ROMM routing on wormhole routed mesh and torus networks. Our simulations show that ROMM algorithms can perform several representative routing tasks 1.5 to 3 times faster than fully randomized algorithms, for medium--sized networks. Furthermore, ROMM algorithms are always competitive with deterministic, oblivious routing, and in some cases, up to 2 times faster.

A balanced ring (b-ring) proposed by Gu et al. [Journal of Systems Architecture, 53, (2007), 902–912.] is more effective than a fault ring (f-ring) in providing fault tolerance for mesh and torus networks. By properly utilizing the b-ring, an efficient fault tolerant routing algorithm can be achieved without using any virtual channel. Traffic congestion can also be significantly reduced. However, the algorithm presented by Gu et al. for the formation of b-ring has the demerits that it involves all the nodes of the network each time a b-ring needs to be formed, and thereby increasing the overhead to the whole system. In this paper, we first present an improved algorithm for the formation of b-ring by considering only the nodes on the fault ring in contrast to all. We next present a distributed algorithm for the same, which is also based on the local knowledge, thereby avoiding overhead and thus, enhancing the overall network performances. We show that our sequential algorithm requires O(|f-ring|) time and the distributed algorithm runs in constant time.

A trustworthy and energy-aware routing protocol in software-defined wireless mesh networks

The paradigm of wireless mesh networks has matured in the last decade after extensive research and development. As opposed to the time of their inception, current mesh networks are expected to deliver carrier-grade access services to their users. With the increasing expectations, it is generally recognized that there is a lack of understanding of the level of service continuity that mesh networks can provide to its users. In this research, we address a set of network design problems and propose solutions to improve the service continuity of wireless mesh networks. First, we investigate power control as a network layer problem in mesh networks. It is commonly acknowledged that reducing transmit power levels of nodes to the minimum required to retain connectivity always increases network capacity. In this work, we show that increasing power level of nodes can be beneficial in many cases depending on network’s traffic and topological characteristics. With extensive analysis and simulations, we characterize achievable spatial reuse and capacity with respect to power control in various practical scenarios. Second, we address the problem of generation of traffic hot-spots in wireless networks, and propose a novel power control scheme for load balancing. Using a heuristic based on the concept of centrality, we show that if we increase the power levels of only the nodes which are expected to relay more packets, significant relay load balancing can be achieved even using shortest path routing. Different from divergent routing schemes, such load balancing strategy is applicable to any arbitrary topology and traffic pattern. With this understanding of power control and load balancing, we investigate the service continuity issues of an urban-scale mesh networks. We define and study two essential service continuity metrics - connection robustness (K-center availability) and performance robustness (K-center performability). K-center availability is the fraction of the time a mesh network is available to its users, while performability is a composite measure of performance (here - throughput) and robustness that captures aggregate experience of mesh users over a long period of time. We develop efficient algorithms for estimating these quantities for large urban-scale meshes and study their characteristics in various existing mesh networks. Our study reveals numerous novel insights that can help in designing mesh networks with high availability and performability. While evaluating the performability, we used ideal case throughput performance estimation that ensures fair network resource allocation among the flows. Although this allows faster computation which is especially necessary for large state space exploration, it is difficult to implement in real-world using CSMA/CA MAC. To address this, we target the issue of unfair and lower utilization of network resources in wireless networks. Specifically, in a mesh network, nodes closer to gateways often achieve a larger share of bandwidth resources while nodes farther away often starve for useful bandwidth. Using back-pressure utility maximization framework, we provide a solution to the issue of spatial bias that can be implemented using current 802.11 standards. To further increase the efficiency of back-pressure policy in mesh networks, we propose a dynamic packet aggregation scheme that is especially effective in Internet-like packet size distribution. Along the same lines, we use the back-pressure invariants to develop a variable channel width assignment scheme that can yield maximum benefits of using varying-sized channels while remaining fair in network-wide resource allocation.

In this paper, we have evaluated the dynamic communication performance of the mesh and torus networks using a open source TOPAZ simulator using virtual cut through switching under uniform traffic pattern. It is found that the torus network yields low latency and high throughput than that of mesh network. Therefore, The dynamic communication performance of the torus network is better than that of the mesh network. The well known phenomenon is justified using a new open source simulator, TOPAZ simulator.

The IEEE 802.16 mesh network, which is self-organized and self-configured with multi-hop, is deployed to providing an effective solution for broadband wireless access system. The standard defines the basic scheduling scheme, but doesn’t specify the resource allocation and routing scheme in the protocol. Therefore, designing a reasonable scheduling and routing algorithm to enhance the capability is very important for the system. In this paper, we propose an efficient and practical routing algorithm which takes the channel condition and modulation mode into consideration in an IEEE 802.16 mesh network. Furthermore, our algorithm enables direct communications between subscriber stations without referring to the base station. Simulation results show that our algorithm effectively improved the scheduling length, delay and system throughput.

A wireless mesh network (WMN) has been popularly researched as a wireless backbone for Internet access with off-the-shelf and inexpensive equipments. Nowadays, several applications like contents sharing, multicast video streaming, vehicular networks encourage to build mesh networks in urban areas. However, the deployment of WMNs in unlicensed bands of dense urban areas imposes many challenges. While previous research has mostly focused on optimal channel allocation under inter or intra-flow interferences within mesh nodes, the practical deployment of WMNs also requires to consider the interference caused by external entities such as residential access points that do not belong to the WMN. To address this issue, we propose Urban-X which is a first attempt towards a new architecture for Multi-Radio Cognitive Mesh Networks. Based on a cross-layer scheme, we develop novel routing and forwarding schemes reflecting the residential traffic state of external users. Through an extensive simulation analysis using the ns-2 simulator, we demonstrate the feasibility of our routing scheme and we show its robustness to the variations of channel environment and external traffics.

Many different factors, such as topology, routing technique, selection function, flow control policy, complexity of router design, contribute to the performance of networks on chip (NoCs). Among these factors, the choice of topology and routing function has a significant effect on the average packet latency and saturation behavior. Torus is popular in many application domains, while the problem of virtual channel misbalance caused by its deadlock avoidance scheme brings lots of performance pathologies. In this paper, we present a novel deadlock avoidance scheme based on draining scheme, and propose a deadlock-free routing scheme for torus networks. We quantify the effects of the proposed routing scheme on the overall network performance by presenting simulation results for 1-D torus and 2-D torus NoCs. Experimental results show that the novel routing algorithm for torus networks could make more efficient use of virtual channel resources, and hence cutting down packet latency and boosting throughput. Note although this paper has considered 1-D and 2-D torus networks in the experimental evaluation, the new scheme is flexible enough to support highradix torus networks.

Routing schemes with the ability to tolerate the faults are important in the massively parallel multiprocessors networks. In this paper, we propose a kind of fault-tolerant routing schemes called positive-first and negative-first (PFNF) for orthogonal concave and convex fault blocks in torus network, which is based on the turn property of PFNF adaptive routing algorithm. In comparison with previous methods, the computation cost of our routing schemes is very low and it can not only easily apply in convex fault block but also in concave fault block, so the disabled healthy nodes can be reduced at the most level. Due to the mutual-switching of turn schemes between two virtual networks, the virtual channel utilization is greatly increased, which is benefic for the traffic-balance and the improvement of system throughput. Sufficient simulation results are presented to demonstrate the effectiveness of the proposed algorithm.

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.

BFRA: bounded flooding routing algorithm for provisioning the globally optimal route in a hierarchical ATM network

The Network-on-Chip (NoC) is Network-version of System-on-Chip (SoC) means that on-chip communication through packet based networks. In NOC topology, routing algorithm and switching are main terminology. The routing algorithm is one of the key factors in NoC architecture. The routing algorithm which defines as the path taken by a packet between the source and the destination. The paper proposes a novel algorithm for a Network-on-Chip, which is based on packet switching. Using square mesh techniques used for 16 nodes based NoC design and simulation. The node is equal to row and column. Paper discusses internal architecture of NoC using addressable memory and simulate on XILINX 14.1 ISE MODELSIM. Keywords : Network-on-Chip, Static routing, Parallelism Cite this Article Anurag Shrivastava, Sudhir Kumar Sharma. A reliable routing architecture and algorithm for network-on-chip, Journal of Electronic Design and Technology . 2015; 6(3): 40–48p.