Computational Network Analysis Research Articles

An algorithm to generate all spanning trees with flow

Spanning tree enumeration in undirected graphs is an important issue and task in many problems encountered in computer network and circuit analysis. This paper discusses the spanning tree with flow for the case that there are flow requirements between each node pair. An algorithm based on minimal paths (MPs) is proposed to generate all spanning trees without flow. The proposed algorithm is a structured approach, which splits the system into structural MPs first, and also all steps in it are easy to follow.

Long-range dependence and heavy-tail modeling for teletraffic data

The analysis and modeling of computer network traffic is a daunting task considering the amount of available data. This is quite obvious when considering the spatial dimension of the problem, since the number of interacting computers, gateways and switches can easily reach several thousands, even in a local area network (LAN) setting. This is also true for the time dimension: Willinger and Paxson (see Ann. Statist., vol.25, no.5, p.1856-66, 1997) cite the figures of 439 million packets and 89 gigabytes of data for a single week record of the activity of a university gateway in 1995. The complexity of the problem further increases when considering wide area network (WAN) data. In light of the above, it is clear that a notion of importance for modern network engineering is that of invariants, i.e., characteristics that are observed with some reproducibility and independently of the precise settings of the network under consideration. In this tutorial article, we focus on two such invariants related to the time dimension of the problem, namely, long-range dependence, or self-similarity, and heavy-tail marginal distributions.

Development of quantitative structure-activity relationship and classification models for a set of carbonic anhydrase inhibitors.

Mathematical models are developed to find quantitative structure-activity relationships that correlate chemical structure and inhibition toward three carbonic anhydrase (CA) isozymes: CA I, II, and IV. Numerical descriptors are generated to encode important topological, geometric, and electronic features of molecular structure. After descriptor generation, multiple linear regression, and computational neural network (CNN) analyses are performed on various descriptor subsets to find superior models for prediction. Committees of five CNNs were utilized to average final predicted values for the 142-compound data set. For inhibitors of CA I, an 8-5-1 CNN committee produced a training set rms error of 0.105 log K(i) (r(2) = 0.994) and prediction set rms error of 0.208 log K(i) (r(2) = 0.980). Training and prediction set rms errors of 0.140 log K(i) (r(2) = 0.992) and 0.231 log K(i) (r(2) = 0.971), respectively, were produced by a 9-5-1 CNN committee for inhibitors of CA II. For prediction of CA IV inhibitors, an 8-5-1 CNN committee produced training and prediction set rms errors of 0.147 log K(i) (r(2) = 0.992) and 0.211 log K(i) (r(2) = 0.991), respectively. In addition, classification models were built using k-nearest neighbor (kNN) analysis to solve two- and three-class problems for inhibitors of CA IV. A three-descriptor classification model proved superior in labeling compounds as active or inactive inhibitors for the two-class problem. Training and prediction set percent classification rates of 100% and 87.1%, respectively, were obtained. For the three-class (active/moderate/inactive) problem, a five-descriptor model was deemed optimal producing a training set percent classification rate of 98.8% and prediction set rate of 79.0%.

Mobility modeling in wireless networks

The movement pattern of mobile users plays an important role in performance analysis of wireless computer and communication networks. In this paper, we first give an overview and classification of mobility models used for simulation-based studies. Then, we present an enhanced random mobility model, which makes the movement trace of mobile stations more realistic than common approaches for random mobility. Our movement concept is based on random processes for speed and direction control in which the new values are correlated to previous ones. Upon a speed change event, a new target speed is chosen, and an acceleration is set to achieve this target speed. The principles for direction changes are similar. Finally, we discuss strategies for the stations' border behavior (i.e., what happens when nodes move out of the simulation area) and show the effects of certain border behaviors and mobility models on the spatial user distribution.

Analysis of Attitudes Toward Computer Networks and Internet Addiction of Taiwanese Adolescents

This study explored the interplay between young people's attitudes toward computer networks and Internet addiction. Ninety possible Internet addicts were selected for examination after analyzing the questionnaire responses of an initial sample of 753 Taiwanese high school adolescents. It was found that the subjects' attitudes toward computer networks could explain many aspects of Internet addiction. However, actual behaviors on Internet usage and perceptions on the usefulness of Internet were more important than affective responses toward computer networks in predicting adolescents' Internet addiction.

DEACON: An Integrated Approach to the Analysis and Design of Enterprise Architecture-Based Computer Networks

The most common approach to network development in the modern organization remains an undocumented, ad hoc method of deploying available technology rapidly to fit within a given cost structure. Current methods largely ignore the importance of integrating the networking strategy of a firm with the overall information systems architecture of the enterprise. To address this problem, a new approach to network analysis and design is presented. The new method integrates existing principles of information systems analysis and design with the unique requirements imposed by distributed systems. The integrated approach seeks to provide the organization with a set of guidelines for allocating resources to a computer network based upon the business goals of a firm. Specifically, the method calls for (1) defining the business problem, (2) modeling business requirements, (3) modeling location requirements, (4) developing a network architecture, (5) simulating network operation, and (6) implementing the network. The method is illustrated and compared to other network development methods. DEACON is found to be an advantageous approach.

Web-based network analysis and design

The gradual acceptance of high-performance networks as a fundamental component of today's computing environment has allowed applications to evolve from static entities located on specific hosts to dynamic, distributed entities that are resident on one or more hosts. In addition, vital components of software and data used by an application may be distributed across the local/wide area network. Given such a fluid and dynamic environment, the design and analysis of high-performance communication networks (using off-the-shelf components offered by third party manufacturers) has been further complicated by the diversity of the available components. To alleviate these problems and to address the verification and validation issues involved in engineering such complex networks, a web-based framework for the design and analysis of computer networks was developed. Using the framework, a designer can explore design alternatives by constructing and analyzing configurations of the design using components offered by different researchers and manufacturers. The framework provides a flexible and robust environment for selecting and verifying the optimal solution from a large and complex solution space. This paper presents issues involved in the design and development of the framework.

Performance analysis of computer networks employing linked-cluster topology with single-wavelength and WDM optical backbones

The present work deals with the analysis of linked-cluster networks with single-wavelength and wavelength-division multiplexed (WDM) optical backbones, providing interconnection between several clusters, wherein each cluster represents a local area network (LAN) with coaxial (coax) cable as the transmission medium. The proposed topology employs 1-persistant CSMA/CD-based media access control (MAC) protocol for coax LANs, and slotted-ALOHA as MAC protocol for single-wavelength optical backbone. In the case of WDM optical backbone slotted-ALOHA and ALOHA are considered as MAC protocols for control and data channels respectively. A novel iterative analytical technique is presented to evaluate the throughputs of individual coax LANs and optical backbone, as well as the end-to-end throughput of entire network. The analysis takes into account the impact of the relevant network parameters, viz. probability of intercluster communication, number of coax LANs, and the coax LAN parameters governing CSMA/CD protocol. The iterative evaluation of throughput is carried out to take into account the effect of the excess traffic in each coax LAN resulting from the intercluster communication. The analysis reveals that the probability of intercluster communications has significant impact on the backbone throughput as well as on the end-to-end throughput of the entire network. For a given coax LAN load, the end-to-end network throughput is found to decrease significantly when the probabilities of intercluster communication in coax LANs exceeds 50%. Further, the analysis shows that one can achieve considerable improvement in backbone throughput when WDM is employed in optical backbone instead of single-wavelength transmission.

A qualitative analysis of computer networks in the British National Health Service

The most senior nurses and midwives in 355 National Health Service (NHS) Trusts in the United Kingdom were surveyed to establish what computer networks were in use by nurses, and what clinical systems and network services were available on these networks, and what training and policies on networks were in place. Qualitative data were also collected; the nurses were asked to comment on network access and possible uses of these networks. This paper concentrates on the qualitative data. The results of the study are being used to influence policy and disseminate information in an action research programme.

Matrix-geometric solutions of M/G/1-type Markov chains: a unifying generalized state-space approach

We present an algorithmic approach to find the stationary probability distribution of M/G/1-type Markov chains which arise frequently in performance analysis of computer and communication networks. The approach unifies finite- and infinite-level Markov chains of this type through a generalized state-space representation for the probability generating function of the stationary solution. When the underlying probability generating matrices are rational, the solution vector for level k, x/sub k/, is shown to be in the matrix-geometric form x/sub k+1/=gF/sup k/H, k/spl ges/0, for the infinite-level case, whereas it takes the modified form x/sub k+1/=g/sub 1/F/sup k//sub 1/H/sub 1/+g/sub 2/F/sup K-k-1//sub 2/H/sub 2/, 0/spl les/k/spl les/K, for the finite-level case. The matrix parameters in the above two expressions can be obtained by decomposing the generalized system into forward and backward subsystems, or, equivalently, by finding bases for certain generalized invariant subspaces of a regular pencil /spl lambda/E-A. We note that the computation of such bases can efficiently be carried out using advanced numerical linear algebra techniques including matrix-sign function iterations with quadratic convergence rates or ordered generalized Schur decomposition. The simplicity of the matrix-geometric form of the solution allows one to obtain various performance measures of interest easily, e.g., overflow probabilities and the moments of the level distribution, which is a significant advantage over conventional recursive methods.

Estimation of packet time belay in high-speed computer networks

Considered is one of the stages of analysis of high-speed computer networks - estimation of time delay of data transmission. Transmission medium is used as the routing network. Given and substained is the stochastic model of estimation of time delay in the data transmission network which is compared to relative model, allows take into account more fully the interaction of information flows. The received analytical dependencies can be used for increasing the efficiency of load control in computer networks

Special issue of Telecommunication Systems on performance modeling and analysis of local computer networks

Special issue of Telecommunication Systems on performance modeling and analysis of local computer networks

Modeling Pipe Networks Dominated by Junctions

The transfer of energy and irreversible energy losses at junctions may dominate flow distribution in pipe networks comprised of connected large‐diameter pipes of short lengths. Neglecting the junction effects when calculating network hydraulics is unacceptable and the use of constant loss coefficients to represent these effects in such networks may not be adequate. In the present study, precise relationships based on experimental data are used to represent the junction‐loss coefficients. These relations, which depend on flow conditions, are incorporated into a computer network analysis model. Significant deviations in flow rates calculated using constant junction loss coefficients and the semiempirical relationships based on experimental data are obtained using an example network characterized by short pipe sections. It is also shown that although there is always a net energy loss at a junction, there may be significant exchange of specific energy from one flow stream to the other. The use of constant loss coefficients is inadequate to account for this phenomenon.

On the modeling and analysis of computer networks

Analytic models for computer network performance evaluation are surveyed. The basics of network analysis are presented, the network design procedure is discussed, and some of the fundamentals of network control are introduced. Some of the issues surrounding the design and behavior of gigabit networks are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Mathematical problems in the theory of shared-processor systems

This article considers new approaches in queuing theory associated with mathematical modelling and analysis of contemporary computer systems and networks using shared processors. Emphasis is placed on results concerning exact determination of probability distributions for such characteristics as sojourn times and waiting times. Various methods of analyzing shared-processor systems are considered, their characteristics analyzed, and special attention is devoted to the broad class of M ¦GI¦1 queuing disciplines that result in Poisson throughput. Several limit theorems for heavyload conditions are described.

Cybernetic Approaches to Computer Communications Networks

Computer networks are very complex and somewhat unpredictable systems in dynamic operations. Cybernetic modelling, incorporating stochastic, fuzzy variables, wherever appropriate, approximating interactions not easily tractable via a black‐box systems approach, may be more accurate. A method of analysis of computer networks is considered by representing subsystems and interactions, accurately as far as possible, and then utilising the results of systems sciences for analysis, including specifics, e.g. queuing systems. The aim is to identify correspondences between the behaviour of subsystems of networks and suitable analytic tools. Automation along such lines for the analysis and design of networks and other systems may be a possibility.

Diffusion approximation of a queueing network with a semi-Markov input

Diffusion approximation for queueing networks with a semi-Markov input is constructed. This approximation can be used in analysis and design of communication and computer networks.

Some limitations of adjacency matrices in computer network analysis

Adjacency matrices have been used to analyze problems with communications in organizations. Although this same approach can be applied to computer communication networks to determine their connectivity, it does have its limitations. This analysis method and its limitations will be discussed in this paper.

Topological reliability analysis of local-area computer networks

This paper examines some aspects of the reliability of several forms of local-area network. An approach derived from graph theory is used to analyse the reliability of a network from link failure, and this method is applied for illustration to four typical network topologies. For a more complete analysis incorporating both link and station failure, a failure-rate model approach is used and is applied in particular to a study of the Ethernet and Cambridge digital ring forms of network.

SYREL: A Symbolic Reliability Algorithm Based on Path and Cutset Methods

Symbolic terminal reliability algorithms are important for analysis and synthesis of computer networks. In this paper, we present a simple and efficient algorithm, SYREL, to obtain compact terminal reliability expressions between a terminal pair of computers of complex networks. This algorithm incorporates conditional probability,, set theory, and Boolean algebra in a distinct approach in which most of the computations performed are directly executable Boolean operations. The conditibnal probability is used to avoid applying at each iteration the most time consuming step in reliability algorithms, which is making a set of events mutually exclusive. The algorithm has been implemented on a VAX 11/750 and can analyze fairly large networks with modest memory and time requirements.