Cellular automaton modeling of computer network

The dramatically increasing growth of computer network has brought us more and more complex systems that reveals plenty of nonlinear complex phenomena. On the other hand, cellular automaton model used to be in the study of a variety of nonlinear and spatially extended systems. This paper proposes a simplified cellular model for computer network, namely the NaSch network model, which is originated at the NaSch model of road traffic. Typically, the NaSch network model is a one-dimension cellular automaton and consists of two kinds of cells, i.e. node cell and link cell. In this paper, the node cell stands for switch nodes in computer network, such as routers and switchers, while the link cell is the abstract of the lines of communication among these switch nodes. The simulation results show that this model indeed captures some of properties of flux of computer networks. The space-time plots illustrate that the randomization in this modeling plays an important role in the emerging of self-organization of congestion. It also demonstrates that the density of packet is another key factor to having influence on congestion. On the contrary, the boundary condition has few contribution to our model.     

Spatio-temporal organization of a cellular automaton model for computer network

It was unveiled by Ren et al. [Comput. Phys. Comm. (2001)] that congestion transition emerges in cellular automaton models for computer network and this NaSch network model with Q=1 has similar behaviours as the NaSch traffic model with maximum velocity v_max=1. For these two NaSch models, the main difference lies in a node cell contained in the NaSch network model. In this paper, we will focus on our further investigation on spatio-temporal organization of the NaSch network model. More interesting phenomena of phase transition are discovered. Firstly, fundamental diagram illustrates that when Q>1 for the NaSch network model it is significantly different from its counterpart, i.e. the NaSch traffic model in a road traffic system. The addition of a node cell, which is allowed to have more than one packets, will lead to generating a new phase. Secondly, in order to characterize phase transition occurred in the NaSch network model, an order parameter is presented with the use of the time average density of nearest-neighbor pairs m. The computational results obtained show that criticality will disappear in a strict sense if noise exists. Finally, two other numerical features, i.e. spatial correlation functions G(r) and relaxation times τ, are analyzed so as to deeply describe behaviours near critical points.     

Broadcast service implementation on a packet-switched network

The implementation of a broadcast service as a basic discussed, and the implementation of the network itself is described briefly. The network already contains novel features, such as the establishment of logical paths between the nodes using a multiline protocol. Algorithms used to implement the service itself are introduced and the way in which the service is used by the network is described. The interface that the service gives towards applications programs is presented and its current use by applications programs is discussed. Future plans for the exploitation of this service are considered.     

Terminal handling protocols in a packet-switched public data network

The diversity of terminals available is a major issue for an administration providing a public data transmission service. The only fair terminal handling policy is to use standard interfaces, and persuade users and manufactures to adapt to these standards, which are the CCITT Recommendations X.25, X.3, X.28, X.29. The virtual call, accessible through X.25, may be the basis of a transport service. Some ways of using PAD services provided by public data networks (in other words of defining protocols between terminal's operator and computer) are: in a real mode of operation, the terminal, seen by the computer through the PAD, looks very much like the real one, or emulates a slightly different one; in a virtual terminal mode, the computer talks to a standard terminal; the mapping of existing real terminals to this virtual terminal is done locally at the user-to-PAD interface, without the computer having to know the specifications of each real terminal; in a PAD-to-PAD mode, the service emulates a direct connection via an asynchronous leased or switched access.     

Transformation of a mealy finite-state machine into a moore finite-state machine by splitting internal states

The problem of transformation of a Mealy finite-state machine (FSM) into an equivalent Moore FSM is considered. This problem often arises in the practice of engineering design, when one needs to avoid direct dependence of the output values on variations in the input values. The proposed approach uses the operation of splitting of internal states of an FSM and represents the machine as a list of transitions. Experiment results have shown that transformation of Mealy FSM into Moore FSM increases the number of internal states, on the average, by a factor of 1.96 and increases the number of transitions by a factor of 2.05; the cost of realization of Moore FSM using an industrial software package is approximately twice as great as the corresponding cost for a Mealy machine. The up-to-date tendencies of development of minimization methods and Moore FSM synthesis are described.     

Optimal resource assignment to maximize multistate network reliability for a computer network

Computer network is a major tool to transmit data in our modern society. How to evaluate and enhance network reliability is thus an important issue for organizations, especially to maximize network reliability. A computer network is a multistate network in which each edge has several possible capacities with a probability distribution and may fail. The multistate network reliability is the probability that the maximal flow is no less than a given demand. From the standpoint of quality management, a further problem is to reassign the existing resources for maximizing multistate network reliability without changing the network topology. Hence, this paper focuses on the resource assignment problem to propose an efficient approach based on the simple genetic algorithm. In which, a resource assignment is represented as a chromosome and the corresponding multistate network reliability is the fitness value of the chromosome. The experimental results show that the proposed algorithm can derive the optimal resource assignment in a reasonable time.     

Visual simulation by means of a transputer network for a driving simulator

Visual simulation is one of the most important parts of a driving simulator. Unfortunately it is in general the most expensive part too. CGI-manufacturers tend to develop more complex systems because of the demands of the military market. The common systems are strongly hardware-oriented. On the basis of a new type of microprocessor, the transputer, a more software-oriented approach is introduced. Transputers in connection with the new high-level language occam are well suited for pipelining and parallelization owing to their communication concept. The advantages of this approach are reduced costs and development time, and also the capability for fast and cheap changes in algorithms. The achievable performance meets the requirements for a driving simulator very well.     

Interconnection of a private packet-switching network and a computer vendor's network

The CSIRO Division of Computing Research has developed an Australia-wide packet switching network, CSIRONET. An interface between CSIRONET and Digital Equipment Corporation's ANF-10 network products has been developed. This interface has been used to connect CSIRONET to the ANF-10 based networks of two Australian Universities. The connections support internetwork terminal and file traffic.     

Analysis of a two-layered network by means of the power-series algorithm

We consider an extension of the classical machine-repair model, also known as the computer-terminal model or time-sharing model. As opposed to the classical model, we assume that the machines, apart from receiving service from the repairman, supply service themselves to queues of products. The extended model can be viewed as a two-layered queueing network, of which the first layer consists of two separate queues of products. Each of these queues is served by its own machine. The marginal and joint queue length distributions of the first-layer queues are hard to analyse in an exact fashion. Therefore, we apply the power-series algorithm to this model to obtain the light-traffic behaviour of the queue lengths symbolically. This leads to two accurate approximations for the marginal mean queue length. The first approximation, based on the light-traffic behaviour, is in closed form. The second approximation is based on an interpolation between the light-traffic behaviour and heavy-traffic results for the mean queue length. The obtained approximations are shown to work well for arbitrary loaded systems. The proposed numerical algorithm and approximations may prove to be very useful for system design and optimisation purposes in application areas such as manufacturing, computer systems and telecommunications.     

Recognizing business cycle turning points by means of a neural network

The latest, 1990–91 recession marks the ninth downturn in the U.S. economy during the past fifty years. There is scope for adding extensions to the methodology of monitoring such major economic fluctuations. The use of artificial neural networks is proposed here. For demonstration a case study is included. In it four key economic indicators are examined; viz., sales, production, employment and personal income. The growth rate movement common to these variables is represented by a state space model of dynamic systems theory. Their monthly time series data over 1965–1989 are simultaneously analyzed. The dates of business cycle peaks and troughs identified in the analysis agree closely with the official chronology.     

The investment acceleration principle revisited by means of a neural network

The investment acceleration principle is a heuristic for modelling a investment time series out of a consumption time series. The model presented herein develops a disaggregated accelerator equation whose coefficients are the weights of a Kohonen neural net that represents firms decision-making. According to this model, investments take place when managers recognise emerging technological patterns. Furthermore, a technique borrowed from the theory of self-organising systems is used in order to disentangle innovation-driven investments from plant-replication investments.     

Traffic routing in a computer network

This paper presents a technique for tuning Decnet networks so as to minimize the average end-to-end packet delay for the entire network. It represent an adaptation of theoretical work on network flows to the realistic case of Decnet. Using this technique to configure hypothetical networks, it then discusses the behaviour of the Decnet routing algorithm with respect to network size, topological connectivity and traffic configuration.     

利用NC机建设高校公共计算机房

分析了高校公共计算机房的现状和存在的问题,介绍了NC机的工作原理,提出利用NC机建设高校公共计算机房。NC机机房能够满足学生的上机要求,而且还能节省成本降低能耗：     

Using minimal cuts to optimize network reliability for a stochastic computer network subject to assignment budget

In our modern society, information and data are usually transmitted through a computer network. Since the computer network's reliability has a great impact on the quality of data transmission, many organizations devote to evaluating or improving network reliability, especially for network reliability optimization. This study focuses on such a confronted problem that is to find the optimal transmission line assignment to the computer network such that network reliability is maximized subject to the budget constraint. Each transmission line owns several states due to failure, maintenance, etc., and thus the computer network associated with any transmission line assignment is called a stochastic computer network. Network reliability is the probability that the computer network can transmit the specified units of data successfully. Because the discussed problem is NP-hard, an optimization algorithm that integrates the genetic algorithm, minimal cuts and Recursive Sum of Disjoint Products is proposed. Experimental results illustrate the solution procedure and show that the proposed algorithm can be executed in a reasonable time.     

Framework of a flexible computer communication network

With the increasing speed of computers and communication links, and the successful convergence of both fields, computers connected by high speed links now represent an enormously large distributed computing system. At the same time, communication between man and machine is also becoming more diverse and personalized. Networking issues such as evolution of user services, seamless communication between hosts, failure recovery and integration of new technologies arise daily. Problem-specific approaches and corresponding solutions are available at considerable cost. However, a common requirement is adaptability of the computer network to a variety of changes. In this paper, we propose Flexible Computer Communication Networks (FN) as a uniform solution to most of these networking problems. The framework of Flexible Networks can be considered as an intelligent shell enclosing existing networking architectures. An agent-oriented implementation of a flexible network is outlined. The conversion of existing networks to flexible networks is shown to be incremental, and therefore practicable.     

析计算机网络的子网划分

对于一个网络,划分子网时,要规划子网的方案,确定子网的数目、子网中支持的最大主机数目以及用于网络段的实际地址。     

The generation of animated motion by means of a recurrent neural network

The possibility to use neural networks to guide animated motion sequences is investigated. The performance of two recurrent architectures, both derived from the cascade-correlation network, is compared. These architectures only differ in the objective function used to train the hidden units. Small differences in performance were observed, but both networks could successfully produce simple motion sequences. An animation environment was created to display arm movement and walking sequences.     

Model reduction of finite-state machines by contraction

This paper discusses an approach to the model reduction of discrete event systems represented by finite-state machines. A set of good reduced-order approximations of a deterministic finite-state machine M can be efficiently computed by looking at its contractions, i.e., finite-state machines constructed from M by merging two states. In some particular case, it is also possible to prove that the approximations thus constructed are infimal, in the sense that there do not exist better approximations with the same number of states. This paper also defines a merit function to choose, among a set of approximations, the best one with respect to a given observed behavior     

浅谈学校计算机网络机房的管理和维护

公共机房的管理与维护是保证学校正常教学活动的基础工作.科学的管理,会使机房维护工作事半功倍.本文根据笔者在中学公共机房十多年来的工作经验,通过对公共机房的软件、硬件设备的管理,系统的维护等方面详尽的阐述,并对在机房管理与维护中经常遇到的问题及解决方法总结出几点建议,可有效提高计算机机房的管理效率.