A protocol for deadlock-free dynamic reconfiguration in high-speedlocal area networks

High-speed local area networks (LANs) consist of a set of switches interconnected by point-to-point links, and hosts linked to those switches through a network interface card. High-speed LANs may change their topology due to switches being turned on/off, hot expansion, link remapping, and component failures. In these cases, a distributed reconfiguration protocol 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. These strategies are called static reconfiguration techniques. 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; 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 protocol that is able to asynchronously update routing tables without stopping user traffic. This protocol is valid for any topology, including regular as well as irregular topologies. It is also valid for packet switching as well as for cut-through switching techniques and does not rely on the existence of virtual channels to work. Simulation results show that the behavior of our protocol is significantly better than for other protocols based on stopping user traffic     

基于人工免疫的工业认知无线网络路由机制

工业互联网（industrial Internet）已成为第四次工业革命的代表技术.根据工业网络数据传输服务的需求,以及针对工业无线网络拓扑相对稳定、流量规律变化等特点,提出了一种基于人工免疫系统（artificial immune system,简称AIS）的工业认知无线网络路由机制,包含基于链路质量的域内静态路由算法和基于多路径的域间动态路由算法,以实现工业网络的可靠路由.根据人工免疫系统特点,将工业网络的拓扑结构进行区域划分：提出了基于链路质量的域内静态路由算法,采用软硬件结合的方式监视网络链路,并根据移动窗口指数加权平均法计算链路丢包率;提出了基于多路径的域间动态路由算法,根据模式距离对节点的流量周期进行预测,防止节点因流量过大而导致丢包.基于OMNET++仿真平台进行仿真实验,结果表明,所提出的路由机制在应对突发流量时与组合定向地理路由算法相比,丢包率及网络开销分别降低1倍;应对链路失效的情况时与图路由算法相比丢包率降低4倍.     

A unified model for joint throughput-overhead analysis of random access mobile ad hoc networks

An analytical framework is developed to study the throughput and routing overhead for proactive and reactive routing strategies in random access mobile ad hoc networks. To characterize the coexistence of the routing control traffic and data traffic, the interaction is modeled as a multi-class queue at each node, where the aggregate control traffic and data traffic are two different classes of customers of the queue. With the proposed model, the scaling properties of the throughput, maximum mobility degree supported by the network and mobility-induced throughput deficiencies are investigated, under both classes of routing strategies. The proposed analytical model can be extended to evaluate various routing optimization techniques as well as to study routing/relaying strategies other than conventional proactive or reactive routing. The connection between the derived throughput result and some well-known network throughput capacity results in the literature is also established.     

公交移动协助城市车载网络分层路由协议

城市车载网络作为未来智能交通的重要组成部分,为解决城市交通问题提供了有效的解决方案.现有大部分路由方案未能很好地解决车辆高速移动、复杂城市交通环境和不同车流密度三大问题对路由转发的影响,导致路由协议的性能在高效和可靠性方面不足.根据城市交通信号传播环境、红灯等停以及公交运行轨迹固定、周期循环等特性,提出公交移动协助的城市车载网络路由协议,将车车之间的复杂、不确定路由转换为普通车辆-簇头-公交三层节点之间的确定、协作方式,发挥公交周期移动优势,并用簇头策略优化普通车辆与公交之间的通信.设计根据城市信号传播衰减与车辆移动相关的单跳链路筛选与多跳延迟相关的概率转发机制,保证公交转发的高效、可靠,并设计能自适应车流密度的簇头触发策略,仿真实验结果表明,整体方案转发跳数达到一定数量时,能取得较好的数据传输成功率和较低的网络延迟.     

基于蚁群算法的可信网络路由

针对不同的网络实际条件,提出一种基于蚁群算法的可信网络路由算法,以寻找网络中任意2个节点间的最优路由。在将链路带宽使用情况作为影响路由重组结果可信度的因素时,同时考虑了路由中节点间链路上的耗费和延时这两个因素,实现了可信的网络路由重组。仿真结果显示,该方法在较快地找到较低耗费和延时路由的同时,能够有效地提高路由重组结果的可信度。     

PDR: A protocol for dynamic network reconfiguration based on deadlock recovery scheme

Dynamic network reconfiguration is described as the process of replacing one routing function with another while the network keeps running. The main challenge is avoiding deadlock anomalies while keeping limitations on packet injection and forwarding minimal. Current approaches which have a high complexity and as a result have a limited practical applicability either require the existence of extra network resources, or they will affect the network performance during the reconfiguration process. In this paper we present a simple, fast and efficient mechanism for dynamic network reconfiguration which is based on regressive deadlock recovery instead of avoiding deadlock. The mechanism which is referred to as PDR guarantees a deadlock-free reconfiguration based on wormhole switching. In PDR, a particular approach is taken to handle both deadlocks and performance degradation. We propose the use of a packet injection restriction mechanism that prevents performance degradation near the saturation by controlling the network traffic. Further, in this approach, to accurately detect deadlocks, the deadlock detection mechanism is implemented and also improved by using only the local information, thereby considerably reducing false deadlock detections. In the rare cases when deadlocks are suspected, we propose a new technique that absorbs the deadlocked packet at the current node instead of dropping deadlocked packets and re-injects it later into the network. The main advantage of this method is its simplicity and also it does not require any additional buffers in intermediate nodes to handle deadlocks. It requires only some buffer space in the local node to temporarily hold the deadlocked packets removed from the network. Evaluating results reveal that the mechanism shows substantial performance improvements over the other methods and it works efficiently in different topologies with various routing algorithms.     

Balancing buffer utilization in meshes using a "restricted area" concept

Adaptive routing and virtual channels are used to increase routing adaptivity in wormhole-routed two-dimensional meshes. But increasing channel buffer utilization without considering even distribution of the traffic loads tends to cause congestion in the most adaptive routing area. To avoid such traffic congestion, a concept of the restricted area is proposed. The proposed restricted area, defined to be a part of the network where message transmission concentrates, can be located following the region of adaptivity. By properly guiding message routing inside and outside the area, we are able to achieve more balanced buffer utilization and to reduce traffic congestion accordingly. The performance of several routing algorithms with or without using the restricted area is simulated and evaluated under various traffic loads and distribution patterns. The results indicate that routing algorithms with the restricted areas yield constantly larger throughput and smaller latency than routing algorithms without using the concept.     

Adaptive inter-layer message routing in 3D networks-on-chip

Existing routing algorithms for 3D deal with regular mesh/torus 3D topologies. Today 3D NoCs are quite irregular, especially those with heterogeneous layers. In this paper, we present a routing algorithm targeting 3D networks-on-chip (NoCs) with incomplete sets of vertical links between adjacent layers. The routing algorithm tolerates multiple link and node failures, in the case of absence of NoC partitioning. In addition, it deals with congestion. The routing algorithm for 3D NoCs preserves the deadlock-free propriety of the chosen 2D routing algorithms. It is also scalable and supports a local reconfiguration that complements the reconfiguration of the 2D routing algorithms in case of failures of nodes or links. The algorithm incurs a small overhead in terms of exchanged messages for reconfiguration and does not introduce significant additional complexity in the routers. Theoretical analysis of the 3D routing algorithm is provided and validated by simulations for different traffic loads and failure rates.     

A Closed-Loop Control Traffic Engineering System for the Dynamic Load Balancing of Inter-AS Traffic

Inter-AS outbound traffic engineering (TE) is a set of techniques for controlling inter-AS traffic exiting an autonomous system (AS) by assigning the traffic to the best egress points (i.e. routers or links) from which the traffic is forwarded to adjacent ASes towards the destinations. In practice, changing network conditions such as inter-AS traffic demand variation, link failures and inter-AS routing changes occur dynamically. These changes can make fixed outbound TE solutions inadequate and may subsequently cause inter-AS links to become congested. In order to overcome this problem, we propose the deployment of a closed-loop control traffic engineering system that makes outbound traffic robust to inter-AS link failures and adaptive to changing network conditions. The objective is to keep the inter-AS link utilization balanced under unexpected events while reducing service disruptions and reconfiguration overheads. Our evaluation results show that the proposed system can successfully achieve better load balancing with less service disruption and re-configuration overhead in comparison to alternative approaches.     

Ad hoc网络中一种带预测的路由算法

在自组网中,由于网络节点的移动性及拓扑结构的易变性,设计稳定的路由成为最受关注的问题。根据可靠性为多路径路由选择更多的可靠路径,以满足自组网中多路径传输在路径的数量和质量方面的需求,是多路径路由技术中的一个重要研究课题。为此,基于GRID模型和预测模型提出了一种带预测的稳定不相交备用路由算法,其利用有效限制路由查询包的泛洪区域,并结合预测策略和节点不相交路径算法来选择一条最稳定的不相交备用路由,从而进一步提高该路由算法的性能。模拟结果显示,与其他3个多路径路由相比较,该算法是一个有效的自组网路由算法。     

Traffic management of a satellite communication network usingstochastic optimization

The performance of nonhierarchical circuit switched networks at moderate load conditions is improved when alternate routes are made available. Alternate routes, however, introduce instability under heavy and overloaded conditions, and under these load conditions network performance is found to deteriorate. To alleviate this problem, a control mechanism is used where, a fraction of the capacity of each link is reserved for direct routed calls. In this work, a traffic management scheme is developed to enhance the performance of a mesh-connected, circuit-switched satellite communication network. The network load is measured and the network is continually adapted by reconfiguring the map to suit the current traffic conditions. The routing is performed dynamically. The reconfiguration of the network is done by properly allocating the capacity of each link and placing an optimal reservation on each link. The optimization is done by using two neural network-based optimization techniques: simulated annealing and mean field annealing. A comparative study is done between these two techniques. The results from the simulation study show that this method of traffic management performs better than the pure dynamic routing with a fixed configuration.     

Context-aware adaptive IP mobility anchoring

The novel distributed mobility management trend is a promising direction to cope with the increasing mobile data traffic and flatten network architectures. Most of the novel mobility approaches distribute the mobility anchors through the access level, as opposed to the centralized mobility anchoring model. Other recent approaches argue that mobility anchors closer to the content servers may be the solution to optimize the mobility performance. However, none of the mobility anchoring models is ideal for all scenarios, since it depends on the user, the session and the network. Hence, we propose an IP mobility approach driven by the context of the user, sessions and the network, where the mobility anchors for IP address allocation and for routing/forwarding are distributed through the network nodes, while the mobility context is managed by the mobile devices. Although each session is properly anchored in the establishment phase, the routing/forwarding is adapted over time, according to the user, the session and the network context: the proposed approach is able to signal different mobility anchors to optimize the routing path to new and ongoing sessions of the user. The outcome of the evaluation shows that the proposed approach overall reduces the data cost, the data delay, the tunneled packets and the tunnel length, when compared with other anchoring models.     

Gunryu III: reconfigurable magnetic wall-climbing robot for decommissioning of nuclear reactor

To perform the decommissioning on the inaccessible area to human workers, the need to develop a wall-climbing robot is increasing. In these wall-climbing robots, high mobility and stability on a surface of walls are most important required features. To achieve both of these features, the new type of arm-equipped reconfigurable multi-modules wall-climbing robot was proposed in this research. The stability and high mobility can be achieved by reconfiguration using attached arm as a connection mechanism. And the robot system composed of two mobile modules and 6DOF manipulator was developed as a proof mechanism. In this robot, for energy efficient and stable mobility at the environment of steel structure, the adsorption method based on magnet was selected and its functionality was confirmed. And, to enable intuitive control, the kinematic solver was developed and verified. Finally, basic experiment of motion test was performed, and it was confirmed that the proposed wall-climbing robot satisfies required functions, such as high mobility and stability.     

Termite-hill: Performance optimized swarm intelligence based routing algorithm for wireless sensor networks

A wireless sensor network (WSN) is a large collection of sensor nodes with limited power supply, constrained memory capacity, processing capability, and available bandwidth. The main problem in event gathering in wireless sensor networks is the formation of energy-holes or hot spots near the sink. Due to the restricted communication range and high network density, events forwarding in sensor networks is very challenging, and require multi-hop data forwarding. Improving network lifetime and network reliability are the main factors to consider in the research associated with WSN. In static wireless sensor networks, sensors nodes close to the sink node run out of energy much faster than nodes in other parts of the monitored area. The nodes near the sink are more likely to use up their energy because they have to forward all the traffic generated by the nodes farther away to the sink. The uneven energy consumption results in network partitioning and limit the network lifetime. To this end, we propose an on-demand and multipath routing algorithm that utilizes the behavior of real termites on hill building termed Termite-hill which support sink mobility. The main objective of our proposed algorithm is to efficiently relay all the traffic destined for the sink, and also balance the network energy. The performance of our proposed algorithm was tested on static, dynamic and mobile sink scenarios with varying speed, and compared with other state-of-the-art routing algorithms in WSN. The results of our extensive experiments on Routing Modeling Application Simulation Environment (RMASE) demonstrated that our proposed routing algorithm was able to balance the network traffic load, and prolong the network lifetime.     

Architecture and operating system support for two-dimensional runtime partial reconfiguration

Reconfigurable machines based on field programmable gate array (FPGA) chips adapt to applications’ needs through hardware reconfiguration. Partial reconfiguration allows the configuration of a portion of a chip while the rest of the chip is busy working on tasks. This paper considers a two-dimensional partially reconfigurable FPGA chip that allows the dynamic swap in and out of circuit modules. Such a chip supports the concurrent execution of multiple applications or an application that is otherwise too large to fit. A challenging issue for 2-D runtime partial reconfiguration is how to support the efficient connection, or routing, between circuit modules or between modules and I/O pins, when those modules may be placed on any area of a chip. Because commercial chips are not efficient in 2-D runtime routing, a new FPGA architecture is proposed based on an array of clusters of configurable logic blocks and a mesh of segmented buses. To evaluate the runtime performance of the architecture, an operating system is specified and implemented which takes care of the scheduling, placement, and routing of circuits on the architecture. Simulation is used to evaluate the efficiency of the OS kernel and to determine the optimal cluster size of the architecture.     

Enhancing Routing Robustness of Unstructured Peer-to-Peer Networks Using Mobile Agents

The growing popularity of Peer-to-Peer (P2P) technology in real applications in recent years has sparked increasing interest from both academia and industry in designing resilient P2P networks for these applications. Routing is a crucial technique to support successful P2P applications, and designing robust routing mechanisms is still a technical challenge for P2P systems and applications due to their inherent dynamics. This paper addresses the issue of resilient routing in unstructured P2P networks. To this end, we first propose a novel query routing approach to improving query performance in unstructured P2P networks, and then develop a mobile agent based network reconfiguration mechanism that provides a combined node and link failure diagnosis and restoration to maintain routing performance even in dynamic network environments. Simulated results show that the proposed query routing approach can achieve a good tradeoff between query hit rates and space costs in scale-free networks and that the mobile agent based network reconfiguration mechanism outperforms the existing methods in different types of network topologies.     

A deadlock-free routing algorithm for dynamically reconfigurable Networks-on-Chip

We address routing in Networks-On-Chip (NoC) architectures that use irregular mesh topologies with Long-Range Links (LRL). These topologies create difficult conditions for routing algorithms, as standard algorithms assume a static, regular link structure and exploit the uniformity of regular meshes to avoid deadlock and maintain routability. We present a novel routing algorithm that can cope with these irregular topologies and adapt to run-time LRL insertion and topology reconfiguration. Our approach to accommodate dynamic topology reconfiguration is to use a new technique that decomposes routing relations into two stages: the calculation of output ports on the current minimal path and the application of routing restrictions designed to prevent deadlock. In addition, we present a selection function that uses local topology data to adaptively select optimal paths.The routing algorithm is shown to be deadlock-free, after which an analysis of all possible routing decisions in the region of an LRL is carried out. We show that the routing algorithm minimises the cost of sub-optimally placed LRL and display the hop savings available. When applied to LRLs of less than seven hops, the overall traffic hop count and associated routing energy cost is reduced. In a simulated 8 × 8 network the total input buffer usage across the network was reduced by 6.5%.     

一种基于OLSR的新型层次路由算法*

提出了一种新型的基于OLSR的层次化改进算法HOLSR,旨在提高OLSR的整体效率。该算法通过分层设置洪泛范围和灵活调整各层拓扑控制分组的更新周期,降低路由执行开销;同时采用差值路由补偿技术提高数据分组的传输效率。仿真实验结果表明：HOLSR与OLSR路由算法相比,数据分组成功传输率高,端到端延迟小,路由协议开销少;与DSR、AODV、DSDV等典型路由算法相比,在不同节点移动速度和不同通信负载下,综合性能也有优势,尤其在通信负载较大时（880 kbps）,优势更加明显。     

Traffic modelling framework for electric vehicles

This article reviews and improves a recently proposed model of road network dynamics. The model is also adapted and generalised to represent the patterns of battery consumption of electric vehicles travelling in the road network. Simulations from the mobility simulator SUMO are given to support and to illustrate the efficacy of the proposed approach. Applications relevant in the field of electric vehicles, such as optimal routing and traffic load control, are provided to illustrate how the proposed model can be used to address typical problems arising in contemporary road network planning and electric vehicle mobility.     

移动环境下实时信道中分散路由方案的容错

分散路由被证明是一个改善网络通信量的有效方法，尤其是在实时系统中。本文讨论了移动环境中分散路由的容错，包括传输错误和移动主机故障。并模拟分析了许多参数对网络通信量结果的影响，如连接故障率、移动主机移动率、移动主机故障率等。