信元调度问题中有优先级的多服务台排队系统

根据排队理论对带有优先级的多服务台信元调度问题进行了定量分析,推导出了每个级别的信元平均时延及丢包率的计算公式,并进行了计算机仿真。根据理论分析和仿真结果,得出了在缓冲区既定的情况下,可以采用提高服务率或者是增加服务台数来有效的降低平均时延和丢包率的结论。由已经得到的公式,可以确定将平均时延及丢包率控制在所允许的范围的服务率和服务台数。     

Optimizing a multiserver queuing system with a variable number of servers

A multiserver Poisson queuing system with losses, with a variable number of servers, and an additive quality functional is investigated. All major characteristic of the system are obtained in an explicit form. __________ Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 92–101, July–August 2007.     

OpenBSD下基于CARP协议的负载均衡防火墙研究

0PenBSD的安全性使其赢得了大量忠实的用户,尤其存网络路由、防火墙上的表蜕,被学校大量作为防火墙（NAT）使用。本系统丛于OpenBSD,利用CARP协议实现了防火墙之间的负载均衡,提高了防火墙的可用性;存实验测试中运行良好、性能稳定。     

A novel robust on-line protocol for load-balancing in structured peer-to-peer systems

In this paper, we revisit the problem of load-balancing structured peer-to-peer systems with on-line protocols. Load-balancing is of major significance for large-scale decentralized networks in terms of enhanced scalability and performance. The main incentives behind balancing schemes are under-utilization of bandwidth and computer resources. Therefore, our methods focus mainly on task-skew. Specifically, we address the problem with on-line protocols on the basis of migration and enhanced availability. In particular, the cornerstones of our methods are the notions of virtual nodes, replication and Multiple realities, combined altogether with allocation techniques based on balls-in-bins games. The rationale of our dynamic protocol to depend exclusively on peer load distribution preserves intact the structural properties and search efficiency of the overlay used as an indexing infrastructure, while preserving the semantic information of the data (e.g., range partitioned network). We also propose an effective load-aware mechanism to facilitate robust operations that counteract against contingent churn failures. Finally, our work is complemented with extensive experiments using both real and synthetic data sets.     

WSN自适应负载均衡集簇分层路由协议

结合考虑传统无线传感器网络(wireless sensor networks,WSN)路由协议特点以及实际应用中节点的不对等性,提出了一种自适应负载均衡集簇分层路由协议——ALBCH.该协议在簇头选举时引入剩余能量等相关因子,将贪婪算法成链机制分别引入分层路由协议的簇内通信和簇头间通信,对贪婪算法成链机制进行了一些改进.仿真结果表明,ALBCH能更有效地均衡网络负载,具有更好的健壮性和更高的实时性能,同时解决了传统协议在处理异构网络时的局限性.     

Grid resource management policies for load-balancing and energy-saving by vacation queuing theory

The resource management is the central component of grid system. The analysis of the workload log file of LCG including the job arrival and the resource utilization daily cycle shows that the idle sites in the Grid are the source of load imbalance and energy waste. Here we focus on these two issues: balancing the workload by transferring jobs to idle sites at prime time to minimize the response time and maximize the resource utilization; power management by switch the idle sites to sleeping mode at non-prime time to minimize the energy consume. We form the M/G/1 queue model with server vacations, startup and closedown to analysis the performance metrics to instruct the design of load-balancing and energy-saving policies. We provide our Adaptive Receiver Initiated (ARI) load-balancing strategy and power-management policy for energy-saving. The simulation experiments prove the accuracy of our analysis and the comparisons results indicate our policies are largely suitable for large-scale heterogeneous grid environment.     

Rough grammar for efficient and fault-tolerant computing on adistributed system

A method that combines global load balancing with dynamic task scheduling on a multiprocessor machine is presented. This method does not require prior knowledge of the run times of tasks, and is based on a rough grammar representing distributed computation is presented. Production rules are dynamically constructed when a concurrent program is run. The set of the rough grammar production rules is updated and rolled in a pipeline fashion, together with codes of the processes. This pipeline fashion of rolling the jobs defines the global job balancing. The rough grammar uses any operators and metrics, not only concatenation, inside its production rules. Performance parameters for the combination of a global load balancing and decentralized dynamic task scheduling are derived and compared with those for a statically scheduled multiprocessor. Based on these parameters, the decentralized methodology is shown to attain a much higher performance level and a highly improved fault tolerance     

Logical clock requirements for reverse engineering scenarios from adistributed system

To reverse engineer scenarios from event traces, one must infer causal relationships between events. The inferences are usually based on a trace with sequence numbers or timestamps corresponding to some kind of logical clock. In practice, there is an explosion of potentially causal relationships in the trace, which limits one's ability to extract scenarios. This work defines a more parsimonious form of causality called scenario causality that concentrates on certain major causal relationships and ignores more subtle, potentially causal links. The influence of an event is restricted to the particular scenario it is part of. An event which is not a message reception is defined to be caused by the previous event in the same software object, while a message reception is caused by a sending event in another object. The events are ordered to form a scenario event graph where typed nodes are events and the typed edges are certain causal relationships. Intuitively, we might say that most logical clocks, which identify events which "happened before" a given event and, thus, are potentially causal, give an upper bound on the set of causal events; scenario causality identifies a lower bound. The much smaller lower bound set makes it possible to reverse engineer and automate the analysis of scenarios     

Efficient contention-based MAC protocol using adaptive fuzzy controlled sliding backoff interval for wireless networks

Efficient medium access control (MAC) protocol should be able to provide high throughput performance and efficient share of the medium. In this paper, a new contention-based MAC protocol based on adaptive fuzzy controlled sliding backoff interval is proposed to maximize the channel throughput and improve the fairness of random access channels. In the proposed protocol, every node that experiences packet collisions increases its sliding backoff interval (SB) range by a forward sliding factor (FSF). In case of successful transmission the node decreases its SB range by a backward sliding factor (BSF). Forward and backward sliding factors are controlled by the channel offered traffic using a fuzzy controller. Furthermore, the operation of the proposed backoff algorithm does not depend on the knowledge of the number of active nodes. A computer simulation is developed using MATLAB to evaluate the performance of the proposed algorithm and compare it with other backoff schemes. Simulation results show that the proposed algorithm significantly outperforms other backoff schemes, such as binary exponential backoff (BEB) and the fast collision resolution (FCR) scheme. It provides a significant efficient fair sharing performance improvement which converges to the ideal fairness performance while providing high throughput performance.     

关键路径优先WSNs负载均衡多路数据传输协议

由于无线传感器网络中节点能量有限,如何实现各节点负载均衡以延长网络生存周期是亟待解决的问题.利用关键路径优先原则提出一种多路径数据传输协议,快速选择适合路径并剔除不适合数据传输的路径,并用剩余能量均衡法为各传送路径分配数据,以有效均衡各节点能量,延长网络生存周期.仿真实验表明:算法显著延长了网络寿命,与其他多路径传输算法相比网络寿命延长超过37%.     

多服务器环境下基于扩展混沌映射的认证密钥协商协议

传统的单服务器环境下基于智能卡认证方案,单个服务器对所有的注册远程用户提供服务。如果用户想要从不同的服务器获得网络服务,则必须分别在不同的服务器注册。为解决以上问题,研究者提出了多服务器认证方案。然而,文献中的大部分方案都不能实现强安全特性。受到切比雪夫映射的半群特性和基于扩展混沌映射的密钥协商协议启发,本文提出一种多服务器环境中的认证方案。新方案不需要使用验证表并且允许用户访问不同的服务器而不需要分别注册。新方案不仅可以抵抗各类攻击,还实现了用户的强匿名性。和以前的相关协议相比,新协议具有高效性和安全性,因而适合在实际环境中应用。     

面向异构集群系统的动态负载均衡技术研究

在集群系统中的一个非常重要的问题就是尽量确保负载的均衡.由于目前的负载均衡算法大多针对同构的集群系统,没有很好的扩展性.研究了异构集群系统,提出了一种异构服务器集群的动态负载均衡算法,并取得了较好的效果,特别是在负载较重的时候.     

A distributed load-balancing policy for a multicomputer

This paper deals with the organization of a distributed load-balancing policy for a multicomputer system which consists of a cluster of independent computers that are interconnected by a local area communication network. We introduce three algorithms necessary to maintain load balancing in this system: the local load algorithm, used by each processor to monitor its own load; the exchange algorithm, for exchanging load information between the processors, and the process migration algorithm that uses this information to dynamically migrate processes from overloaded to underloaded processors. The policy that we present is distributed, i.e. each processor uses the same policy. It is both dynamic, responding to load changes without using an a priori knowledge of the resources that each process requires; and stable, unnecessary overloading of a processor is minimized. We give the essential details of the implementation of the policy and initial results on its performance. Our results confirm the feasibility of building distributed systems that are based on network communication for uniform access, resource sharing and improved reliability, as well as the use of workstations without a secondary storage device.     

基于APON的上行接入分析及其硬件设计

针对APON提出了一种媒体接入控制（MAC)协议。该协议的设计遵照ITU—T有关APON的G．983定义的帧结构。该协议能支持CBR、VBR、ABR和UBR等多种业务．并能保证用户公平地接入和充分利用网络资源。其中CBR／VBR业务的优先级较高．同时也确保ABR业务至少能以最小信元速率通信，系统的剩余带宽被分配给UBR业务。最后，给出了硬件实现框图。     

A system for testing protocol implementations

A large amount of effort is being put into developing international standards for protocols and services in support of Open Systems Interconnection. All this activity will, however, be in vain unless products are produced in conformance with these standards. In order to give users confidence in the products they buy, implementations need to be tested by a trusted independent assessment centre.NPL is currently developing suitable testing techniques for use by such centres. This paper describes the theoretical basis which has been established for this work. This then sets the context within which NPL's current system development plan is discussed.     

一类排队服务系统的最优控制策略研究

建立一个双阈值排队服务模型, 用来协调顾客的等待时间和服务系统的运行成本. 采用一种精细的概率分解方法获得瞬态和稳态队长的概率分布性质; 再根据系统稳态性能指标, 建立系统营运利润函数, 并设计一种针对双离散变量函数的全局优化收索算法来研究最优控制策略; 进一步的数值实验揭示出双重阈值策略的优越性.     

A load-balancing algorithm for a parallel electromagnetic particle-in-cell code

Particle-in-cell simulations often suffer from load-imbalance on parallel machines due to the competing requirements of the field-solve and particle-push computations. We propose a new algorithm that balances the two computations independently. The grid for the field-solve computation is statically partitioned. The particles within a processor's sub-domain(s) are dynamically balanced by migrating spatially-compact groups of particles from heavily loaded processors to lightly loaded ones as needed. The algorithm has been implemented in the quicksilver electromagnetic particle-in-cell code. We provide details of the implementation and present performance results for quicksilver running models with up to a billion grid cells and particles on thousands of processors of a large distributed-memory parallel machine.     

A dynamic load-balancing scheme for the parcel hub-scheduling problem

In this paper, a dynamic load-balancing algorithm (DLBA) was proposed to solve the parcel hub-scheduling problem (PHSP), which is a combinatorial optimization problem commonly found at a parcel consolidation terminal in the parcel delivery industry (PDI). The problem consists of processing a large number of inbound trailers at a much smaller number of unload docks. The parcels in the inbound trailers must be unloaded, sorted and transferred to the load docks, and loaded onto the outbound trailers. Because the transfer operation is labor intensive and the PDI operates in a time-sensitive environment, the unloading, sorting, transferring, and loading of the parcels must be done in such a way as to minimize the timespan of the transfer operation. A DLBA that considered the state of the system was proposed and evaluated to schedule the inbound trailers to the unload docks. The performance of the algorithm was compared to the performance of an efficient static load-balancing algorithm (SLBA) and to an existing lower bound. An experimental analysis shows that the DLBA offers solutions that are 8.6% better than the solutions offered by the SLBA for large-size problems and that the average computational time is only 1.34 min for the DLBA compared to 15.04 min for the SLBA.     

A randomized algorithm for the joining protocol in dynamic distributed networks

We describe a randomized algorithm for assigning neighbours to vertices joining a dynamic distributed network. The aim of the algorithm is to maintain connectivity, low diameter and constant vertex degree. On joining each vertex donates a constant number of tokens to the network. These tokens contain the address of the donor vertex. The tokens make independent random walks in the network. A token can be used by any vertex it is visiting to establish a connection to the donor vertex. This allows joining vertices to be allocated a random set of neighbours although the overall vertex membership of the network is unknown. The network we obtain in this way is robust under adversarial deletion of vertices and edges and actively reconnects itself.