Heterogeneous Computer Networks Research Articles

Network intrusion detection

Intrusion detection is a new, retrofit approach for providing a sense of security in existing computers and data networks, while allowing them to operate in their current "open" mode. The goal of intrusion detection is to identify unauthorized use, misuse, and abuse of computer systems by both system insiders and external penetrators. The intrusion detection problem is becoming a challenging task due to the proliferation of heterogeneous computer networks since the increased connectivity of computer systems gives greater access to outsiders and makes it easier for intruders to avoid identification. Intrusion detection systems (IDSs) are based on the beliefs that an intruder's behavior will be noticeably different from that of a legitimate user and that many unauthorized actions are detectable. Typically, IDSs employ statistical anomaly and rulebased misuse models in order to detect intrusions. A number of prototype IDSs have been developed at several institutions, and some of them have also been deployed on an experimental basis in operational systems. In the present paper, several host-based and network-based IDSs are surveyed, and the characteristics of the corresponding systems are identified. The host-based systems employ the host operating system's audit trails as the main source of input to detect intrusive activity, while most of the network-based IDSs build their detection mechanism on monitored network traffic, and some employ host audit trails as well. An outline of a statistical anomaly detection algorithm employed in a typical IDS is also included.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A comparative study of PVM workstation cluster implementations of a two-phase subsurface flow model

Four versions of a message-passing, distributed-memory, distributed-disk multicomputer application for simulating two-phase fluid flow in porous media are studied. The FORTRAN 77 finite element code, solved in parallel using an iterative domain-decomposition method, was ported from a shared-memory multiprocessor implementation to a network of heterogeneous computers using the PVM (Parallel Virtual Machine) software system. Issues concerning the calculation of speedups in cluster computing are discussed, and the performance of the four versions is compared. Parallel efficiencies of up to nearly 60% were achieved using 17 homogeneous networked workstations; speedups were comparable to the shared-memory implementation. We conclude that network multicomputing using PVM is an attractive alternative to hardware multiprocessors for large-grained parallel implementations of computationally intensive problems in hydrology.

Towards a distributed finite element package for electromagnetic field computation

The transformation of a finite-element program into a distributed application, allowing its users to handle the remote computational power available on a heterogeneous network of computers, is presented. Tools are designed to facilitate the client/server decomposition and implementation for a finite-element package like FLUX3D, and it is shown that one can improve the performances of such an application by use of distributed computing. Many difficulties are discussed, such as the localization of resources, the replicated database management, the cost of network communications, and parallel distributed computing. The model in which a single remote server running on a powerful host is used to perform coarse grained computations seems to give the best performances. Because of communication times, parallel distributed computing is less efficient. Moreover, it requires a real programming effort (leading to little transparency) when being implemented in a steady-state finite-element package.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Network‐based concurrent computing on the PVM system

AbstractConcurrent computing environments based on loosely coupled networks have proven effective as resources for multiprocessing. Experiences with and enhancements to version 1.0 of PVM (Parallel Virtual Machine) are described in this paper. PVM is a software package that allows the utilization of a heterogeneous network of parallel and serial computers as a single computational resource. This report also describes an interactive graphical interface to PVM, and porting and performance results from production applications.

Hetero Helix: Synchronous and asynchronous control systems in heterogeneous distributed networks

Hetero Helix is a programming environment which simulates shared memory on a heterogeneous network of computers. The machines in the network can vary with respect to their native operating systems and internal representation of numbers. Hetero Helix was designed to present in simple programming model to developers, and also considers the needs of designers, system integrators, and maintainers. The key software technology underlying Hetero Helix is the use of a ‘compiler’ which analyzes the date structures in shared memory and automatically generates code which translated data representations from the format native to each machine into a format understood by all machines, and vice versa. This automatic code generation insures correctness and eases the burden on code developers, who would otherwise have to do the same job by hand. Hetero Helix has been used successfully in connection with an integration effort involving 27 CPUs in a heterogeneous network and a body of software totalling roughly 100,000 lines of code.

A network multi-processor for experiments in parallelism

Although both shared memory and loosely coupled parallel computing systems are now common, many still do not offer an easy way to design, implement, and test parallel algorithms. Our system provides software tools that make possible a variety of connection structures between processes. These structures are said to form a 'Network Multi-Processor', which is implemented on a local area network of heterogeneous UNIX-based timesharing computers, plus a set of processor boards dedicated to an application so that accurate timing measurements can be made. We explain how these tools have been used both to aid parallel algorithm development and to explore the properties of different computer interconnection methods.

NETMATE: A network management environment

A description is given of the Network Management Analysis and Testing Environment (NETMATE) project, the prime goal of which is to develop a unified and comprehensive software environment for network management to oversee and orchestrate the operations of diverse devices and protocols in large, heterogeneous computer networks. The overall NETMATE architecture is discussed, and the network management functions performed by each component are described. The problem of network modeling and the NETMATE approach to it are presented. The current implementation status of NETMATE is given, and some conclusions are offered. >

Preface

Virtual Machine/Enterprise Systems Architecture™ (VM/ESA™) represents the next major milestone in the history of the VM family of operating systems. It is a single product that supports both centralized and distributed computing systems in a way that preserves data integrity and protects shared resources. Operating systems of this kind are essential to the use of computers today, as more and more computers are linked and are sharing resources and data across more and more networks of heterogeneous computers and systems. Centralized computing, distributed computing, and the resulting concerns about access, sharing, and recovery of data and resources have seen dramatic increases in recent history and are expected to continue unabated. VMIESA is designed to bring together the three main branches of the VM family in support of these requirements. This special issue has an essay and six papers on various aspects of this subject. We are indebted to E. A. Pruul and L. P. Augostini of the Endicott Programming Laboratory in Endicott, New York, for their valued support of this special issue.

Heterogeneous computer network for real-time hemodynamic signal processing

A computer network is described that allows real-time processing, graphical monitoring and off-line analysis of blood pressure, nervous activity and Doppler signals recorded in conscious rats. Real-time processing is performed by an acquisition station using a powerful microprocessor, allowing extraction and storage of several characteristic parameters from each cardiac cycle and real-time graphical monitoring. The experimenter can thereby follow the time evolution of the hemodynamic parameters. Experimental data are sent through the local network to a workstation that ensures off-line processing such as chronograms, histograms and statistical analyses.

A delay-based approach for congestion avoidance in interconnected heterogeneous computer networks

In heterogeneous networks, achieving congestion avoidance is difficult because the congestion feedback from one subnetwork may have no meaning to sources on other subnetworks. We propose using changes in round-trip delay as an implicit feedback. Using a black-box model of the network, we derive an expression for the optimal window as a function of the gradient of the delay-window curve.The problems of selfish optimum and social optimum are also addressed. It is shown that without a careful design, it is possible to get into a race condition during heavy congestion, where each user wants more resources than others, thereby leading to a diverging condition.It is shown that congestion avoidance using round-trip delay is a promising approach. The approach has the advantage that there is absolutely no overhead for the network itself. It is exemplified by a simple scheme. The performance of the scheme is analyzed using a simulation model. The scheme is shown to be efficient, fair, convergent, and adaptive to changes in network configuration.The scheme as described works only for networks which can be modeled with queueing servers with constant service times. Further research is required to extend it for implementation in practical networks. Several directions for future research have been suggested.

Diplans: a new language for the study and implementation of coordination

In this paper the reader is introduced to coordination in the workplace as an object of scientific study and computer automation. Diplans are the expressions of a new graphical language used to describe plans of operation in human organizations. With diplans, systems of constraint, which may or may not take the form of procedure definitions, can be specified. Among the special strengths of diplans is their ability to render explicit the interactive aspects of complex work distributed over many people and places—in other words, coordination. Diplans are central to coordination technology, a new approach to developing support for cooperative work on heterogeneous computer networks.

A method for interconnecting heterogeneous computer networks

AbstractThe real problems of network interconnection lie in the management of heterogeneity. The heterogeneity is not confined to the mechanical protocols but to much wider issues such as service philosophy (connection‐orientated vs connectionless), addressing, routing, applications models, management facilities and the foresight of the network designers in allowing for interconnection with alien networking systems.This paper describes a system which interconnects two heterogeneous networking environments through a third (local) system. Application layer relaying was chosen to provide the services of computer mail and remote terminal access. The interconnection architecture uses special network front‐ends and a local area network to provide a flexible and manageable system. A transport service interface is used to provide functional separation between the front‐ends and general purpose computers, including the relays.

An environment for rule-based blackboards and distributed problem solving

This work describes COPS, an environment for distributed problem solving in networks of heterogeneous computers. COPS is intended for problems with coarse grains of parallelism. Communication among processes is by messages. A modified production system model permits rule-based blackboards to be constructed. Ambassadors are used to provide remote processes with access to blackboards.

A formal method for composing a network command language

A formal method is introduced for the development and definition of command languages for heterogeneous computer networks. The network command languages are developed from the command languages of the systems constituting the network. This is done by defining a common presentation model for the system command languages and constructing the network command language by applying a composition principle to the commonly represented languages. The common presentation model is defined as a Vienna Development Method (Meta IV) abstract processor for command languages. System command languages are represented by means of predicate functions which are defined on the abstract domains of the abstract processor. This allows a straightforward formulation of the composition principle as a function for the logical combination of predicate functions. Two sample network command languages are composed out of two hypothetical command languages. The results are related to the International Organization for Standardization Open Systems Interconnection model (ISO OSI).

Fault diagnosis and automatic reconfiguration for a ring subsystem

Abstract A ring subsystem has been developed for a full-scale high performance heterogeneous computer network. The design goals and the implementation issues of the automatic reconfiguration of the ring subsystem are presented. Particular emphasis is laid upon reliability improvement techniques, based on duplication of the ring subsystem components, and the automatic reconfiguration algorithm, which determines network configuration when faults occur.

Some critical considerations on the ISO/OSI RM from a network implementation point of view

The paper outlines the conceptual and practical aspects encountered in the design and implementation of a heterogeneous computer network based on the standardization output. We discuss the feasability of the reference model and its related standards from a design, implementation and operational point of view focussing on the adopted solutions and their rationales.

Network security considerations in BLN

In a heterogeneous computer network, resources on each node are protected by the local security mechanism. Network services allow local resources to be accessed remotely from other nodes. Without appropriate network security measures, each node is vulnerable to attack from the network. This paper analyzes the heterogeneous Bell Labs Network (BLN) environment and lists the potential network security risks. By assessing the risks, counter-measures are proposed for minimizing potential exposure. These counter-measures are part of a global network security mechanism being implemented for BLN.

The DARPA Internet: Interconnecting Heterogeneous Computer Networks with Gateways

The DARPA Internet: Interconnecting Heterogeneous Computer Networks with Gateways

A distributed approach to the interconnection of heterogeneous computer networks

This paper describes a distributed architecture for the flexible interconnection of heterogeneous networks with a number of mini- and micro computers, in a research environment. The interconnected networks include the DARPA Internet, which uses the DoD protocols, and the X25-based networks PSS and SERCNET. The approach described here distributes the network access into a set of microcomputers acting as network frontends ("network access machines"), with a local area network (Cambridge Ring) as a common bus. Communication between the hosts and the network access machines uses an interprocessor communication mechanism with a standard transport-level virtualcall interface, which is described. This arrangement provides local hosts with flexible access to any of the networks, and supports a relay system which allows users on one network to access hosts and facilities on any of the other networks.

Network data management for heterogeneous computer networks: the virtual file concept

Possible system architectures for data access and transfer in computer networks are reviewed. Owing to the considerable differences between the types of data management system used in heterogeneous networks, the definition of a network data management system free of local constraints seems to be the most practical approach for standardized file-oriented communication. The proposed network data management system is designed to operate in an open system environment (ISO/TC97/SC16) and will be implemented in two interconnected networks.