Dynamic Affinity Cluster Allocation in a Shared Disks Cluster

A shared disks (SD) cluster couples multiple computing nodes for high performance transaction processing, and all nodes share a common database at the disk level. In the SD cluster, a front-end router selects a node for an incoming transaction to be executed. An affinity-based routing can increase the buffer hit ratio of each node by clustering transactions referencing similar data to be executed on the same node. However, the affinity-based routing is non-adaptive to the changes of the system load. This means that a specific node would be overloaded if corresponding transactions rush into the system. In this paper, we propose a new transaction routing algorithm, named Dynamic Affinity Cluster Allocation (DACA). DACA can make an optimal balance between the affinity-based routing and indiscriminate sharing of load in the SD cluster. As a result, DACA can increase the buffer hit ratio and reduce the frequency of inter-node buffer invalidations while achieving the dynamic load balancing.     

基于NPV广义超立方体最佳容错路由算法

在网络可靠性研究中,设计较好的容错路由策略、尽可能多地记录系统中最优通路信息,一直是一项重要的研究工作.超立方体系统的容错路由算法分为可回溯算法和无回溯算法.一般说来,可回溯算法的优点是容错能力强:只要消息的源节点和目的节点有通路,该算法就能够找到把消息传递到目的地的路径;其缺点是在很多情况下传递路径不能按实际存在的最短路径传递.其代表是深度优先搜索(DFS)算法.无回溯算法是近几年人们比较关注的算法.该算法通过记录各邻接节点的故障信息,给路由算法以启发信息,使消息尽可能按实际存在的最短路径传递.这些算法的共同缺点是只能计算出Hamming距离不超过n的路由.在n维超立方体系统连通图中,如果系统存在大量的故障,不少节点对之间的最短路径大于n,因此,这些算法的容错能力差.提出了一个实例说明采用上述算法将遗失60%的路由信息.另外,由于超立方体的结构严格,实际中的真正超立方体系统不多.事实上,不少的网络系统可转换为具有大量错误节点和错误边的超立方体系统.因此,研究能适应具有大量错误节点和错误边的超立方体系统的容错路由算法是一个很有实际价值的工作.研究探讨了:(1) 定义广义超立方体系统;(2) 在超立方体系统中提出了节点通路向量(NPV)概念及其计算规则;(3) 提出了中转点技术,使得求NPV的计算复杂度降低到O(n);(4) 提出了基于NPV的广义超立方体系统最佳容错路由算法(OFTRS),该算法是一种分布式的和基于相邻节点信息的算法.由于NPV记录了超立方体系统全部最优通路和次最优通路的信息,在具有大量故障的情况下,它不会遗漏任何一条最优通路和次最优通路信息,从而实现了高效的容错路由.在这一点上,它优于其他算法.     

A simple fault-tolerant adaptive and minimal routing approach in 3-D meshes

In this paper we propose a sufficient codition for minimal routing in 3-dimensional (3-D) meshes with faulty nodes,It is based on an early work of the author on minial routing in 2-dimensional(2-D) meshes,Unlike many traditional models that assume all the nodes know global fault distribution or just adjacent fault information,our approach is based on the concept of limited global fault information,First,we propose a fault model called faulty cube in which all faulty nodes in the system are contained in a set of faulty cubes.Fault information is then distributed to limited number of nodes while it is still sufficeint to support minimal routing.The limited fault information collcted at each node is represented by a vector caaled extended safety level.The extended safety level associated with a node can be used to determine the existence of a minimal path from this node to a given destination .Specifically,we study the existence of minimal paths at a given source node,limited distribution of fault information,minimal routing,and deadlock-free and livelock-free routing.our results show that any minimal routing that is partially adaptive can be applied in our model as long as the dstination node meets a certain conditon.We also propose a dynamic planar-adaptive routing scheme that offers better fault tolerance and adaptivity than the planar-adaptive routing scheme in 3-D meshes.Our approach is the first attempt to address adaptive and minimal routing is 3-D meshes with faulty nodes using limited fault information.     

基于负载均衡算法的Hyperledger Fabric共识机制研究

Hyperledger Fabric将业务逻辑解耦,在提升系统灵活性的同时存在性能瓶颈,无法满足高并发快响应的业务需求。通过对Hyperledger Fabric共识机制中的背书、排序、验证3个阶段进行分析,为均衡背书节点性能并提高系统效率,设计基于动态负载均衡算法的提案分发优化方案。综合均衡指数、反馈周期等性能指标,设计节点负载和节点权值量化方法。通过采集节点负载信息计算并选取合理的反馈周期和影响权重以更新节点权值,同时结合加权轮询算法将交易提案分发至当前权重最大的节点进行背书,实现背书节点负载的动态均衡。在Caliper工具上的测试结果表明,优化方案提升了Hyperledger Fabric共识机制的请求处理性能,相比于原始方案的链码交易和查询吞吐量提高了17.53%和15.84%,平均时延下降了6.7%和18.2%。     

Performance evaluation of transaction processing couplingarchitectures for handling system dynamics

As the demand for high volume transaction processing grows, coupling multiple computing nodes becomes increasingly attractive. This paper presents a comparison on the resilience of the performance to system dynamics of three architectures for transaction processing. In the shared nothing (SN) architecture, neither disks nor memory is shared. In the shared disk (SD) architecture, all disks are accessible to all nodes while in the shared intermediate memory (SIM) architecture, a shared intermediate level of memory is introduced. A transaction processing system needs to be configured with enough capacity to cope with the dynamic variation of load or with a node failure. Three specific scenarios are considered: 1) a sudden surge in load of one transaction class, 2) varying transaction rates for all transaction classes, and 3) failure of a single processing node. We find that the different architectures require different amounts of capacity to be reserved to cope with these dynamic situations. We further show that the data sharing architecture, especially in the case with shared intermediate memory, is more resilient to system dynamics and requires far less contingency capacity compared to the SN architecture     

一种累计多路径的移动自组网络路由策略

描述了一种基于多路径移动自组网络按需路由策略.在移动自组网络,由于网络节点的移动性及拓扑结构的易变性,路由成为最受关注的问题.在以前的移动自组网络路由算法中,主要采用的是传统的单路径方式.最近,多路径方式也逐渐出现,因为相对单路径路由而言,多路径为移动自组网络提供的QoS支持更可行、更高效.鉴于现有的移动自组网络多路径策略未能为源节点提供充分的信息,提出了一种新型的移动自组网络多路径路由算法.该算法可以将路由信息保存在源节点中,并依此在源节点中采用替换路径或多路径并发的方式进行数据传输.     

Full-Information Lookups for Peer-to-Peer Overlays

Most peer-to-peer lookup schemes keep a small amount of routing state per node, typically logarithmic in the number of overlay nodes. This design assumes that routing information at each member node must be kept small so that the bookkeeping required to respond to system membership changes is also small, given that aggressive membership dynamics are expected. As a consequence, lookups have high latency as each lookup requires contacting several nodes in sequence. In this paper, we question these assumptions by presenting a peer-to-peer routing algorithm with small lookup paths. Our algorithm, called “OneHop,” maintains full information about the system membership at each node, routing in a single hop whenever that information is up to date and in a small number of hops otherwise. We show how to disseminate information about membership changes quickly enough so that nodes maintain accurate complete membership information. We also present analytic bandwidth requirements for our scheme that demonstrate that it could be deployed in systems with hundreds of thousands of nodes and high churn. We validate our analytic model using a simulated environment and a real implementation. Our results confirm that OneHop is able to achieve high efficiency, usually reaching the correct node directly 99 percent of the time.     

基于Sun SPOT平台的无线传感器网络多跳路由协议设计

多跳路由协议是无线传感器网络中的关键技术之一,针对传统多跳传输协议在无线传感器网络的实际应用中存在部署过程过于复杂等问题,设计了一种灵活实用的基于Sink节点控制的无线传感器网络多跳传输协议(Sink Controlling Multi-hop Protocol,SCMP)。Sink节点通过发送命令信息实现对传感器节点的控制,并收集各个节点的路由信息从而获得全局路由,然后对传感器节点的数据传输进行进一步控制。在Sun SPOT平台上对SCMP进行了部署实验,结果表明,基于Sink节点控制的多跳传输协议更加方便灵活,在实际的无线传感器网络应用中具有一定的有效性和可行性。     

Robust load-balanced backbone-based multicast routing in mobile opportunistic networks

Mobile opportunistic network (MON) is an efficient way of communication when there is no persistent connection between nodes. Multicast in MONs can be used to efficiently deliver messages to multiple destination nodes. However, because multiple destination nodes are involved, multicast routing is more complex than unicast and brings a higher communication cost. Backbone-based routing can effectively reduce the network overhead and the complexity of routing scheme. However, the load of backbone nodes is larger than that of regular nodes. If the backbone node’s buffer is exhausted, it will have a significant impact on the performance of the routing scheme. Load balancing can improve the ability of backbone to deal with the change of network load, and backbone maintenance algorithm can provide backbone robustness. In this paper, we propose a robust load-balanced backbone-based multicast routing scheme in MONs. In the backbone construction algorithm, we transform the problem of backbone construction into a multi-objective optimization problem, and propose a multi-objective evolutionary algorithm-based backbone construction algorithm, namely LBMBC-MOEA algorithm. In addition, in order to increase the robustness of the backbone-based routing scheme, we propose a localized multicast backbone maintenance algorithm (MBMA) to deal with the buffer exhaustion of backbone nodes. When a backbone node’s residual buffer is insufficient, MBMA algorithm selects other nodes to replace the backbone node. The results on extensive simulations show that when considering the node buffer size constraints, compared with previous backbone-based multicast routing schemes, our proposed algorithm has better performance, and when the node’s residual buffer is insufficient, MBMA algorithm can significantly improve the performance of the backbone-based multicast routing scheme.     

基于中间轴的WSN双线路由机制

针对现有的基于虚拟坐标的路由协议不能本地感知、数据传输易受阻及能量消耗不均衡等缺点,设计了一种基于中间轴的双线路由机制,利用网络的中间轴为每个节点分配虚拟坐标,并在该虚拟坐标上实施双线路由机制。用户节点可以在不知道源节点位置的情况下找到自己感兴趣的数据,而且可以在复杂环境中确保数据的发送,有效解决其他路由协议中空洞边界或公共节点的通信热点问题。通过实验,对节点负载的规范化标准偏差及高负载节点数量进行计算,结果表明,设计的方法能获得较好的负载平衡,避免网络热点产生。     

一种最优的静态路径编码存储策略

路径编码方案通过记录从XML文档根结点到当前结点的路径信息,可以快速判断结点间的各种位置关系.高效的编码存储策略可以在提高存储空间利用率的同时,减少系统的IO开销,从而进一步提升系统的整体性能.提出一种最优的静态路径编码存储策略,其基本思想是在存储编码中的数字时,每个编码中数字对应的前缀并非提前给定,而是根据其所在数字区间中数字的使用频率之和给定相应的前缀,因此可以充分利用每个不同数字的频率信息来降低所需的存储空间.最后通过实验结果验证了该方法的可行性及有效性.     

Effects of node processing time on optimal load balancing in tree hierarchy network configurations

In this paper, optimal static load balancing in a tree hierarchy network that consists of a set of heterogeneous host computers is considered. It is formulated as a nonlinear optimization problem. By parametric analysis, we study the effects of the node processing time on the optimal link flow rate (i.e. the rate at which a node forwards jobs to other nodes for remote processing), the optimal node load (i.e. the rate at which jobs are processed at a node), and the optimal mean response time. We show that the entire network can be divided into several independent sub-tree networks with respect to the link flow rates and node loads. We find that the processing time of a node affects only the link flow rates and the loads of nodes which are in the same sub-tree network. Generally, an increase in the processing time of an arbitrary node causes an increase in the link flow rates of its ancestor nodes and itself, but causes a decrease in the link flow rates of its descendant nodes and its collateral nodes in the same sub-tree network. It also causes a decrease in the load of the node itself, but causes an increase in the loads of other nodes in the same sub-tree network. Furthermore, it causes an increase in the mean response time. By conducting numerical experiments, we find that the node processing time possesses a large influence on the system performance measures. Knowledge of the effects of node processing time is useful in designing networks or making a parametric adjustment to improve the system performance.     

A performance model of a design for a minimally replicated distributed database for database-driven telecommunications services

In intelligent networking telecommunication services such as free-phone and various personal communications services, the dialed number corresponds to the identity of the called party rather than to the called party's physical location. The dialed number must therefore be converted to a routable telephone number during call setup. This accomplished by querying a database. If the query is successful, its result is a routable number which is passed to the switch at which the call originates so that the call may be completed. A database maintained solely at a single node may not be sufficient to support the large capacity, reliability, and rapid processing requirements of this service. However, these requirements may be met by replicating and distributing the database instead.Replication and distribution induce problems of consistency, concurrency, and load balancing. We describe and present a performance model of a scheme for replicating customer profiles efficiently. To spread the query transaction load, the database and its replicates could be distributed over a set of geographically distinct nodes. The database would be partitioned into as many disjoint fragments as there are nodes. Each fragment would be stored at two of the nodes, subject to the constraint that no pair of subsets would be stored at more than one node. This constraint ensures that the load which would have been carried by a failed node is spread to two other nodes instead of one, thus reducing the risk of overload in case of failure. We also use a performance analysis to arrive at heuristics for routing transactions within the database which attempt to minimize the query and update response times. For a particular implementation, the analysis suggests that READ or query transactions should be routed to the least loaded node of those holding the fragment of interest. By contrast, when strict locking of all copies is required while performing an update, WRITE or update transactions which are initiated at one node and repeated at the other should be routed to the more heavily loaded of the nodes to minimise overall response time. Recommended by: Amit ShethA shorter version of this paper was presented at the 8th ITC Specialist Seminar on Universal Personal Telecommunications held at Santa Margherita Ligure, Italy, in October 1992.     

An Adaptive Routing Algorithm for WK-Recursive Topologies

This paper presents an easy and straightforward routing algorithm for WK-recursive topologies. The algorithm, based on adaptive routing, takes advantage of the geometric properties of such topologies. Once a source node S and destination node D have been determined for a message communication, they characterize, at some level l, two virtual nodes and that respectively contain S but not D and D but not S. Such virtual nodes characterize other (where is the node degree for a fixed topology) virtual nodes of the same level that contain neither S nor D. Consequently, it is possible to locate triangles whose vertices are these virtual nodes with property to share the same path, called the self-routing path, directly connecting to . When the self-routing path is unavailable to transmit a message from S to D because of deadlock, fault, and congestion conditions, the routing strategy can follow what we call the triangle rule to deliver it. The proposed communication scheme has the advantage that 1) it is the same for all three conditions; 2) each node of a WK-recursive network, to transmit messages, does not require any information about their presence or location. Furthermore, this routing algorithm is able to tolerate up to faulty links. Received: July 19, 1998; revised May 17, 1999     

MDCE路由算法的分析与改进

延迟容忍网络中基于位置的地理路由算法使用节点自我采集的GPS信息进行下一跳中继结点的选择,而节点的移动性会导致节点的实际位置在时刻改变,相对位置节点的移动方向信息比地理位置信息具有更好的稳定性。文献[1]提出的MDCE路由算法网络负载率和丢包率很高,且由于DTN网络的特殊性,难以拥有多个相邻节点。对MDCE路由算法进行分析与改进,降低中继节点数、规避消息副本向来的方向传输。仿真结果表明,改进后的MDCE路由算法的网络负载率和丢包率明显降低,实用性更强。     

Randomized dynamic route maintenance for adaptive routing in multihop mobile ad hoc networks

Several approaches have been proposed for designing multihop routing protocols in mobile ad hoc networks (MANET). Many of them adopt a method, called flooding, to discover a routing path. Due to the time-varying nature of the route in MANET, the discovered route needs to be dynamically maintained for optimality in terms of traffic load, hop-distance, and resource usage. It is easy to see that flooding incurs significant overhead and hence is inappropriate for the dynamic route maintenance. In this paper we propose a randomized, dynamic route maintenance scheme for adaptive routing in MANET. The scheme makes use of a nomadic control packet (NCP) which travels through the network based on a random walk, and collects its stopovers as a traversal record. The NCP uses the traversal record to probabilistically provide the nodes with clue for routing path updates. From the clue, the nodes can find the routing path update information that is up-to-date and optimal (less-loaded and shorter), thereby adapting to the dynamic network topology and traffic load conditions. We present an analytical model for measuring the effectiveness of NCP in terms of its frequency of visits and probability of finding the clue from the NCP traversal record. The proposed randomized scheme serves as a routing protocol supporting layer and can be easily applied with minimum modifications to the existing on-demand routing protocols such as AODV and DSR. In our experimental study, we modified the AODV protocol to maintain routing paths using NCPs’ traversal record. Simulation results show that NCPs help the routing protocol to notably reduce average end-to-end packet delay with increased route optimality and better control on traffic congestion.     

双向主从式Chord资源搜索算法的研究

Chord是一种结构化的P2P网络模型,它具有速度快、无需中心控制、可扩展性强、负载平衡、高容错性能等优点。但是,Chord查找算法为单向查找,当目的节点与当前节点距离较远时,需经多次跳转,增加了路由延迟;Chord中能力较弱的节点来负责系统中大量的查询和下载,以及节点随时加入或离开系统的频繁变迁情况,这样会造成网络查询效率明显下降。改进的算法即双向主从式Chord算法支持双向搜索,并将网络中的节点分为超级节点和普通节点,由评估结果值较高的超级节点组成Chord主环。通过实验证明,改进算法有效地减少了路由跳数,降低了网络延迟。     

Depth-first search approach for fault-tolerant routing in hypercubemulticomputers

Using depth-first search, the authors develop and analyze the performance of a routing scheme for hypercube multicomputers in the presence of an arbitrary number of faulty components. They derive an exact expression for the probability of routing messages by way of optimal paths (of length equal to the Hamming distance between the corresponding pair of nodes) from the source node to an obstructed node. The obstructed node is defined as the first node encountered by the message that finds no optimal path to the destination node. It is noted that the probability of routing messages over an optimal path between any two nodes is a special case of the present results and can be obtained by replacing the obstructed node with the destination node. Numerical examples are given to illustrate the results, and they show that, in the presence of component failures, depth-first search routing can route a message to its destination by means of an optimal path with a very high probability     

Shortest-path routing in randomized DHT-based Peer-to-Peer systems

Randomized DHT-based Peer-to-Peer (P2P) systems grant nodes certain flexibility in selecting their overlay neighbors, leading to irregular overlay structures but to better overall performance in terms of path latency, static resilience and local convergence. However, routing in the presence of overlay irregularity is challenging. In this paper, we propose a novel routing protocol, RASTER, that approximates shortest overlay routes between nodes in randomized DHTs. Unlike previously proposed routing protocols, RASTER encodes and aggregates routing information. Its simple bitmap-encoding scheme together with the proposed RASTER routing algorithm enable a performance edge over current overlay routing protocols. RASTER provides a forwarding overhead of merely a small constant number of bitwise operations, a routing performance close to optimal, and a better resilience to churn. RASTER also provides nodes with the flexibility to adjust the size of the maintained routing information based on their storage/processing capabilities. The cost of storing and exchanging encoded routing information is manageable and grows logarithmically with the number of nodes in the system.     

移动自组网基于跨层协作的负载均衡队列调度算法

传统的路由协议都是基于"最短路径"的考虑,节点在对数据包进行调度转发的时候,无条件的为路由控制消息赋予较高的优先转发权,这样就会导致网络中处于骨干位置的节点负载过重,从而进一步影响整个网络的性能.本文提出一种新的基于跨层协作的负载均衡队列调度算法(CLLBS),通过在MAC层与网络层监视节点网络负载,配合路由协议,根据节点的负载状况实时动态地对数据流的转发优先权进行调整,在整个网络进行负载均衡,缓解那些拥塞节点的负载压力.仿真结果表明本文算法较之传统的简单优先权算法有明显的性能提高,可以有效地提高网络的吞吐量,降低丢包率.