时控令版协议在分布式系统临界区访问中的应用

分布式系统临界区互斥访问方法大体上有集中式算法、分布式算法和令版环算法三种。本文在简单讨论了这三种方法后,结合在分布式光纤数据接口FDDI中应用的时控令牌协议,对令版环算法进行了改造,使得令版特环一周的时间可以控制在有限范围内,从而为丢失令牌的判断提供了理论依据。模拟实验对改进引起的综合影响进行评价,认为该改进是可取的。     

一种改进的双令牌互斥算法

互斥是解决分布式系统中资源申请的相互冲突、实现资源共享的一种有效方法.文中对目前的一些互斥算法进行了介绍,并对集中式互斥算法和分布式互斥算法进行了讨论,并分析了其特点.在简要介绍令牌环算法和双令牌算法的思想和步骤后,提出一种改进的双令牌算法.详细叙述了改进算法的设计思想和实现步骤,对性能进行了分析并给出算法示例.讨论结果表明,与原有的双令牌算法相比,新算法可以以更高效率有效检测令牌丢失并实现令牌重构.     

一体化承载网络的互斥问题研究*

一体化承载网是一种全新的网络体系架构,其以网络承载服务为核心,结合可重构路由平台技术,根据用户的业务需求,在现有的物理网络上构建逻辑承载网。但构建逻辑网时,会产生分布式公用资源访问的互斥问题。针对一体化承载网络的体系结构,设计了一种基于令牌的互斥算法。该算法借鉴解决旅行商问题的算法思想,构造一个逻辑环,使得令牌遍历所有节点的代价最小,并提出了一种新的基于请求的令牌传递策略,能有效降低系统中的通信量。最后对算法进行了模拟仿真。     

分布式互斥算法的研究与改进

在几种基于令牌算法的基础上,提出了一个对网络逻辑结构无要求的分布式互斥算法。算法不但能够在逻辑结构无要求的计算机网络中通过发送消息和传递令牌来同步对临界资源的访问,而且可以很好地解决请求丢失、令牌丢失等问题。通过对算法的性能进行分析验证了该算法是高效的,并给出了正确性证明。     

一种基于ARCNET网络的DCS通信控制器的令牌管理机制

介绍了一种DCS通信控制器的网络通信接口硬件,论述了其中使用的令版管理机制,详细讨论了令牌争用、逻辑环形成和重组等技术,同时也对软件编程进行了说明。     

令牌桶算法比较研究

令牌桶算法是流量整型的重要方法,该文在对令牌桶算法作了分析的基础上,对IETF的两种令牌桶算法：单速率三色标记算法和双速率三色标记算法进行了研究。对算法的性能进行了比较分析,并用仿真实验对不同算法的输出流与参数值之间的关系作了研究．揭示了不同算法中参数设置的内在关系。     

令牌总线局域网中逻辑环维护算法的改进

在令牌总线局域网络中,当逻辑环被破坏时,就要运行逻辑环维护算法。逻辑环维护算法的效率是影响网络实时性的重要因素,也是令牌总线局域网络投入实用的主要难点。本文提出一种逻辑环维护算法。该算法采用“后继站地址搭载的技术”,降低了逻辑环维护的复杂性,减少了逻辑环维护所用的时间,使网络的实时性得以保障。     

分布式系统临界区的时控令牌访问算法及其排队模型

文章结合在分布式光纤数据接口FDDI中应用的时控令牌协议,对现有分布式系统临界区互斥访问的令牌环算法进行了改造。并对改进后的系统模型进行了分析,建立了相应的排队模型,并对一种简化模型L／D／1／1／FCFS（相关）进行了解析和模拟实验。模拟实验结果显示时控令牌协议下的系统稳定状态是两个稳定状态交替出现形成的。     

基于令牌桶算法的卫星数据地面传输流量控制方法研究

该文根据卫星数据的特点,在研究令牌桶算法的基础上,提出了一种改进的令牌桶算法,增加了两个模块:令牌放置模块和令牌请求模块,在模拟环境下实现该算法。在对卫星数据进行流量控制的同时,降低了数据传输过程中的抖动,并保证了卫星实时数据的低时延和非实时数据尽量大的带宽,在模拟环境下进行测试,达到了较好的效果。     

基于OODA环的分布式作战仿真时间管理算法

在信息化战争时代,OODA指挥控制环在军事仿真中的应用日益广泛,分布式仿真的灵活性及高效的并行性对作战仿真的发展提供了便利。面对作战仿真的需求,对分布式仿真系统的核心技术——时间管理算法进行研究。针对OODA指挥控制环的特点,提出了一种自适应移动时间窗算法。算法根据模型自适应调整时间窗大小,可避免频繁同步并对内存进行精准清除。为进一步优化时间管理算法,提出了一种改进全局虚拟时间算法,对全局虚拟时间同步计算中的阻塞过程进行改善。详细分析该算法的步骤及原理,并通过实例进行验证。结果表明,该算法可有效保证分布式仿真的运行,运行速度优于其他传统时间管理算法。     

RMP: fault-tolerant group communication

Based on a logical token ring, this communication protocol ensures total message ordering and atomic delivery, so all group members maintain an identical view of ordered events. RMP (Reliable Multicast Protocol) is an efficient multicast protocol for general distributed applications based on the logical token ring approach. The novelty of RMP is that it simultaneously multicasts an ordered message and implicitly rotates the token position on the ring. There is no token transfer message in the normal multicast. For message atomicity, our protocol minimizes control messages and communication costs while incurring a relatively short delay. In contrast to other token algorithms, RMP does not risk losing the token when the token site fails. Without requiring extra overhead, our approach guarantees total ordering of messages and message atomicity-either every member receives a message, or none do     

HUSTRING网络的双环结构及其路由算法

环形局域网HUSTRING采用令牌传递和寄存器插入相结合的媒介访问控制协议,从而获得了优于令牌环的实时传输性能。本文介绍了HUSTRING 的双环结构,研究了它的拓扑容错性能,并给出其信息包路由选择算法。     

Using Logical Rings to Solve the Distributed Mutual Exclusion Problem with Fault Tolerance Issues

In this paper, we investigate distributed mutual exclusion algorithms and delineate the features of a new distributed mutual exclusion algorithm. The basis of the algorithm is the logical ring structure employed in token-based mutual exclusion algorithms. Specifically, there exists dynamic properties of the logical ring that, given certain restrictions regarding message traffic flow, passively give useful information about the location of the token. Effectively, the algorithm demonstrates a type of intelligent routing that identifies useful shortcuts in the routing of the token. The result is a reduction in the total number of messages exchanged prior to the execution of the critical section as compared to the algorithm proposed by Fu and Tzeng [3]. Furthermore, the algorithm allows for an increased degree of fairness in a lightly loaded system than that allowed by Fu and Tzeng's algorithm. The paper also addresses failure recovery issues.     

H-R网络安全系统结构

文章首先分析了等级式+环形体系结构的特点，并在此基础上提出分布式安全体系结构方案：H-R网络安全系统结构。通过使用等级式结构，保证整个体系良好的可扩展性；通过使用安全令牌环协议(运行在环型结构中)，提高体系结构的健壮性，并简单介绍了安全令牌环协议的实现。最后对该体系结构进行了分析。     

分布式工业测控网DMCN中多主站组成的逻辑环维护算法

分布式工业控制网中采用多主站组成的令牌总线逻辑环，当逻辑环被破坏时，就执行逻辑维护算法。算法效率直接影响整个网络的效率，也是影响网络实量性的主要因素。本文针对这种类型的网络，提出了一种新的算法，采用“下站地址捎带”，从而降低整个网络逻辑环维护复杂性，使维护逻辑环时间得以减少，使网络的实时性得以保证。     

Real-time fault tolerant operation of the 802.5 token ring

Scheduling a hard real time application on a token ring requires that the delays to capture the token be known. Previous studies considered only a small subset of the token ring mechanisms in schedulability analyses. In this paper, we study the influence of three types of faults on the time to capture the token. These are token losses, failures of the active monitor and cable faults. We also show the influence of the stack mechanism on the delay to capture the token. The paper ends with an evaluation of these delays in various ring configurations in which the transmission speed, token hold time and ring latency are variables. We conclude that the token ring may be very difficult to schedule for hard real time applications because we do not know if other mechanisms or combinations of phenomena can introduce additional delays that make the operation of the ring unpredictable in the present state of knowledge.     

Implementation of a Reliable Multicast Protocol

A reliable multicast protocol (RMP) based on a logical token ring approach can achieve agreement of a group of operational processes in distributed systems. The structure of RMP is modulated into component protocols that achieve total ordering, atomicity of multicast messages; dynamic group configuration and fault-tolerance cooperatively. RMP uses a virtual token to order multicast messages in a logical process ring. It is highly efficient over networks and its algorithm design and implementation are presented. The use of a state machine approach simplifies this complex system implementation. Experience and lessons drawn from RMP and general techniques applied to group communication protocol are also described. © 1997 John Wiley & Sons, Ltd.     

Synchronous bandwidth allocation in FDDI networks

It is well known that an FDDI token ring network provides a guaranteed throughput for synchronous messages and a bounded medium access delay for each node/station. However, this fact alone cannot effectively support many real-time applications that require the timely delivery of each critical message. The reason for this is that the FDDI guarantees a medium access delay bound to nodes, but not to messages themselves. The message-delivery delays may exceed the medium-access delay bound even if a node transmits synchronous messages at a rate not greater than the guaranteed throughput. We solve this problem by developing a synchronous bandwidth allocation (SEA) scheme which calculates the synchronous bandwidth necessary for each application to satisfy its message-delivery delay requirement. The result obtained in this paper is essential for effective use of the FDDI token ring networks in supporting such real-time communication as digital video/audio transmissions, and distributed control/monitoring     

一种广域网中的分布式互斥算法

广域网可简单地看作由多个局域网通过远程通信线路互连组成。为了适应广域网环境的特点,文章提出了一种两层结构的分布式互斥算法模型,把广域网系统组织成由局部进程组成的局部网络的由每个局部网络中的协调进程组成的全局两层。为了互斥地访问共享资源,局部进程必须首先获得局部令牌,然后再向本地协调进程申请全局令牌,只有获得了局部和全避令牌的局部进程才能进入临界区。还讨论了对该算法可能的扩展。     

Simple token ring local area network

The implementation of a simple token ring system is described. A token ring is a form of local area network in which hosts must capture the token, a unique bit pattern, to use the communications medium. Many existing token ring implementations designate a separate host as a monitor station for the ring. Thus ring initialization and recovery are centralized, so it the monitor is down the ring becomes unusable.Our aim was to build a simple cheap token ring which would have advantages over an Ethernet-style local area network in terms of guaranteed access time upper bounds. We also attempted to decentralize initialization and recovery by giving each host the ability to initialize and repair the ring.