In this paper the authors present the challenges for enabling security policies management and subsequent ubiquitous access control on the personal network (PN) environment. A solution based on security profiles is proposed, supporting both partially distributed architectures-having in this case distributed master devices acting as access points- and also pure peer-to-peer interactions inside the PN. Taking benefit from the modularity and scalability of the design, this solution can be extended into supporting coalitions of different security domains, deriving from the creation of PNs federations

The purpose of this paper is to propose a methodology for defining database navigation rules with the help of the XML language. This enables the introduction of the concept of the dynamic application server - a server that can be instantiated with the help of a relevant, "database-descriptive" XML document and acquire from it all the necessary knowledge for performing queries on the particular database. In order to support those ideas, the paper presents several hierarchical models: business application information model, database model and database navigation model. In the end, those models are integrated into a single, concrete model that eases the definition and creation of three-tier business applications, whose main characteristic is the easy adaptation to any legacy database.

A personal area network environment is a wireless ad hoc data communication system that allows a number of independent data devices to communicate. A more and more wireless devices will be used in the near future. These devices form an ad-hoc environment whose security issues are very critical. The robustness and adaptability will become the key issues to accomplish security in ad hoc wireless network. Security should be applied in all levels of the system, but main concern of this paper is to tackle this issue mainly by means of secure communication in higher layers and how it could be possible to maintain the user profile and share specific services and application with other PANs. There is a need of enhanced security via application in order to achieve seamless communication between several devices not only over the same personal area network. Some desirable properties such as authentication and privacy that can prevent the information of the users from flowing to others is considered through this application.

Abstract Textile manufacturers have to monitor the quality of their products in order to maintain the high‐quality standards established for the clothing industry. Thus, textile quality control is a key factor for the increase of competitiveness of their companies. Textile faults have traditionally been detected by human visual inspection. However, human inspection is time consuming and does not achieve a high level of accuracy. Therefore, industrial vision units are of strategic interest for the textile industry as they could form the basis of a system achieving a high degree of accuracy on textile inspection. This work describes the software core of a system designed for fabric inspection on the basis of simple image‐processing operations as well as its efficiency on detection of usual textile defects. The prerequisites of the overall system are then discussed analytically, as well as the limitations and the restrictions imposed due to the nature of the problem. The software algorithm and the evaluation of the first results are also presented in details. Copyright © 2001 John Wiley & Sons, Ltd.

This paper concerns the design and development of an available bit rate (ABR) server as part of an asynchronous transfer mode (ATM) switch. The overall implementation is based on a shared medium switching architecture, a time division multiplexed (TDM) bus, providing both modularity and high reliability. The paper focuses on hardware architecture of the entire system and presents its basic software architecture.

During the last few years, the mobile wireless industry has been spending considerable effort to enhance the technical characteristics of existing second generation systems in the goal of upgrading their service provision capabilities and of promoting effective integration with data transport networks (the GSM GPRS is an obvious paradigm). This line of action can be anticipated as a first step in the migration path towards 3G systems and has been adopted for two basic reasons: the first is that market demand for wireless data services is currently a small portion of the overall wireless service demand and the second is that the deployment of new technologies in large scale requires gross economical investments. This paper proposes a protocol architecture, a physical configuration and a set of functions for DECT cell clusters that provide access to ISDN transport networks. It also proposes a scheme for the incorporation of these clusters in the numbering and mobility support schemes of existing GSM networks.

The performance evaluation of broadband networks requires statistical analysis and modeling of the actual network traffic. Since multimedia services, and especially variable bit rate (VBR) MPEG-coded video streams are expected to be a major traffic component carried by these networks, modeling of such services and accurate estimation of network resources are crucial for proper network design and congestion-control mechanisms that can guarantee the negotiated quality of service at a minimum cost. The layer modeling of MPEG-1 coded video streams and statistical analysis of their traffic characteristics at each layer is proposed, along with traffic models capable of estimating the network resources over asynchronous transfer mode (ATM) links. First, based on the properties of the entire MPEG-1 sequence (frame layer signal), a model (Model A) is presented by correlating three stochastic processes in discrete time (autoregressive models), each of which corresponds to the three types of frames of the MPEG encoder (I, P, and B frames). To simplify the traffic Model A and to reduce the required number of parameters, we study the MPEG stream at a higher layer by considering a signal, which expresses the average properties of I, P, and B frames over a group of picture (GOP) period. However, models on this layer cannot accurately estimate the network resources, especially in multiplexing schemes. For this reason, an intermediate layer is introduced, which exploits and efficiently combines information of both the aforementioned layers, producing a model (Model B), which requires much smaller number of parameters than Model A and simultaneously provides satisfactory results as far as the network resources are concerned. Evaluation of the validity of the proposed models is performed through experimental studies and computer simulations, using several long duration VBR MPEG-1 coded sequences, different from that used in modeling. The results indicate that both Models A and B are good estimators of video traffic behavior over ATM links at a wide range of utilization.

In recent years the world has witnessed an unprecedented expansion in the global audio-visual industry and actions have been initiated to strengthen its actors, especially in film-making and video production. Companies seeking ways to improve their performance and productivity and become more competitive are investing in modern digital technologies. Very powerful high-performance computing systems are found today even in small production facilities. Yet, little effort has been used to implement activities other than production/post-production and even less, to integrate the whole cycle of content development and creation within a networked collaborative environment. This paper reports the experience of the DAViD project, aiming to establish ways to interact and collaborate during pre-production phases. Several benefits have been demonstrated such as reduction of the overall production time and cost, increased productivity and increased ability to execute complex, multi-company productions in shorter times and lower budgets.

Fast resource management (FRM) is a traffic control function which will be used for short-term bandwidth management in ATM networks. It aims at the minimisation of the time required to reserve the necessary resources before allowing a connection to exploit them. Two different approaches, the FRM with immediate transmission and the FRM with delayed transmission are described and their performance is evaluated through comparative simulation study. The immediate transmission is in all cases superior, especially in the presence of increased round-trip delay. The usage of the FRM, as imposed by the end users', the applications' and the telecom operators' requirements, are also discussed.

Protocols such as the real-time transport protocol (RTP), are used to provide suitable voice/video communication channels over the Internet. RTP transports real-time media data along with synchronization information over a datagram protocol such as the user datagram protocol (UDP). The Casner-Jacobson (see Internet-Draft, 1997) RTP/UDP/IP header compression algorithm can significantly reduce the overhead and increase the throughput of a connection. We evaluate the behavior of header compression in noisy links. It is shown that error indication and error correction can improve the resilience of header compression over noisy links.

Signalling functionality is considered as a necessary feature of B-ISDN networks for the support of connection oriented services between end users. Signalling channels are established between the network and the user and are active throughout the lifetime of the data connections, providing a dedicated service control and monitoring path across the network. This paper elaborates the implementation issues to be followed for the development of broadband terminals supporting ATM signalling functionality and exhibits a novel architecture based on sockets communication, which allows any user connected to a distributed network (e.g. LAN) to take advantage of the provided ATM services. It also presents the method that was adopted to test the signalling stack for conformance against the specifications. Finally, the paper concludes with the presentation and an extensive discussion of evaluation performance measurements obtained during the most basic signalling operations.

One of the technological concepts with significant contribution to the evolution of digital telecommunications in the last decades is the ISDN concept. ISDN protocols serve as the main basis for the development of new techniques and technologies for the implementation of complex, advanced digital based services over the existing telecommunications infrastructure. This paper proposes a generic ISDN based platform capable of supporting state of the art BRI and PRI applications incorporating all the latest network management and inter-working developments in the field.

In this paper an efficient heuristic routing algorithm is proposed that increases the network throughput irrespective of the network traffic load. Its effectiveness is based on an efficient cost metric, which achieves a successful trade-off between the use of the minimum-hop routes and the load balancing. Moreover, it employs the known trunk reservation concept according to probability that increases linearly as the traffic load increases. This results in an effective compromise of the performance of the algorithm between light and heavy loads. Finally its simplicity and its suitability for a real-time application render it as an efficient routing algorithm for ATM networks.

This paper performs issues relative to modeling of VBR MPEG coded video sources over ATM B-ISDN networks. Firstly, we analyse the statistical characteristics of the three types of frames, which the MPEG algorithm generates, and we study their autocovariance and probability density functions. Based on the data analysis, we propose two new source models which approximate both the statistical properties and the traffic characterization of MPEG sequences. The second source model (model B) has been introduced in order to reduce significantly the number of parameters which are necessary for our modeling. To verify the good fitness of the proposed new models, a statistical multiplexing configuration over ATM B-ISDN networks has been implemented and cell as well as frame loss probability have been estimated when the bit stream of video sources is generated by the real data and the two proposed models.

The traffic policing in ATM networks is one of the most critical preventive congestion control mechanisms. It intends to ensure that each source conforms to its traffic parameters negotiated during the call admission control phase. We enhance the known leaky bucket mechanism with a learning algorithm in order to police the distribution of the traffic, observing the values that the counter of the leaky bucket takes. As is shown, tighter and faster control is achieved by the proposed methodology for any type of traffic source, resulting in more statistical gain and better guarantee of the QoS constraints.

This paper describes the design and implementation of a PC terminal supporting ATM signalling and its incorporation in an ATM test-bed for the provision of multimedia services. It presents the method that was adopted to test the signalling stack for compliance to the respective specifications. The role of signalling functionality in service provision is also assessed, both from the functional and performance evaluation point of view. The ATM terminal service provision capabilities were demonstrated with a real-time video distribution application and resulted in one of the first experiments, involving a multimedia application integrated with the signalling protocol stack infrastructure.

The asynchronous transfer mode (ATM) is viewed as the emerging technology capable of delivering new interactive multimedia services to residential users. Despite the business risks, the vigorous investments by the technology and telecommunications industries and the content owners, clearly demonstrate the belief that digital video and interactive television are going to happen. On the other hand, the provision of Internet access to home users through an ATM access network is seemed to be required, due to the wide adoption of the Internet. Considering the DAVIC reference configuration and the LAN emulation standard, an end-to-end ATM urban architecture providing interactive multimedia services is shown to be able to provide Internet access to residential users as well. A couple of different approaches to provide access to Internet are presented.

The paper contributes to currently debated key issues on the evolution of ATM networks and their standardisation. It takes the view that since the asynchronous transfer mode has features of both circuit and packet switching, one has to selectively draw benefits for different types of traffic, compromising, if necessary, the integration principle. The use of the available bit rate (ABR), promoted by the ATM Forum for handling time insensitive (best effort) traffic, is fully adopted and its influence on switching discussed in detail. Coupled with ABR for transmission, the paper supports the employment of massive memory within the switching equipment. By suggesting solutions to key memory management problems, it also examines the use of X.25-like flow and congestion control, selectively employed for data transfer over ATM networks.

Management architectures as well as protocols for accessing managed entities and exchanging management information are well developed in standards. On the other hand developments in open distributed processing (ODP) are of recognized importance for network and service management. Their generic features fit well into the geographically extended, multiple vendor and heterogeneous environment of communication networks. As a third ongoing development asynchronous transfer mode (ATM) broadband integrated services digital networks (B-ISDN) offer challenging problems for resource allocation, network performance and quality of service (QoS) evaluation in real time. The paper shows how performance monitoring and evaluation for ATM networks can greatly profit from the features of a distributed system environment (DSE). The extreme flexibility offered by the ATM principle requires a rich and reusable set of servers accomplishing coordinated performance evaluation tests. DSE transparencies are an excellent match to corresponding management applications (MA) requirements, so that tests can be performed in a distributed, flexible and adaptable way under a conceptually simple architecture. The paper draws extensively from a non-distributed counterpart, i.e. an existing sophisticated ATM test and analysis tool developed under the "Research for Advanced Communications in Europe" (RACE) program, R1083 PARASOL project.>

The paper models and evaluates key design issues for the Adaptation Layer in ATM networks. The role and efficient design of the adaptation layer is crucial for future B-ISDN based on ATM. We concentrate on packet-mode adaptation services analyzing and simulating relevant protocols employed for narrowband ISDN signaling and packet data. Processing and transmission resources are modeled. In particular we investigate the performance of software based solution resident in microprocessors and interfaces to the ATM world via a generic interface component. This set-up which is currently under development is found adequate to handle narrowband ISDN signaling and data traffic. It offers a cost effective and readily available solution for the transition phase towards fully customized broadband components.

Connectionless (CL) services as already developed in LANs, have to interwork with emerging asynchronous transfer mode (ATM) connection-oriented (CO) networks. MANs are a significant evolutionary step and CO MANs, in particular, constitute a technically appealing method to integrate both environments and provide shared medium access for all services. The functions required for enhancing distributed-queue dual-bus (DQDB) MANs with CO services in a way compatible with ATM are described. Within the integrating framework of B-ISDN, the practically useful scenarios for interworking LANs, CO and CL MANs, and ATM are investigated and classified in order to exploit the advantages of an efficient protocol relay utilizing the resources of the lowest possible layer. This is aimed at assisting interworking unit (IWU) designers and implementors to decide on key options in this versatile and evolving environment. The CO DQDB case emerges as the most advantageous development in terms of interworking simplicity and robustness.>

The authors examine the internetworking of the distributed queue dual bus (DQDB) metropolitan area network (MAN) with asynchronous transfer mode (ATM) of broadband integrated services digital network (B-ISDN). Several scenarios are discussed. It is suggested that the best solution is through the use of a connection-oriented (CO) DQDB service. Some of the provisions of the CO DQDB service necessary for an efficient and simple interworking are provided.>

The cost of a dedicated fiber access to the B-ISDN is too high for small business and residential customers, necessitating some form of resource sharing. Combining ATM over a passive optical network (APON) with a suitable medium access control (MAC) protocol can provide significant cost savings and a reasonable bandwidth. In this way, this customer section can also enjoy introduction of broadband services at a relatively early stage. The emphasis of the MAC protocol presented is placed on service transparency with an aim to incur minimal changes to the local exchange (LEX) when an APON is attached. Sharing is effected by a reservation-based time division multiple access method.>

The dynamic routing problem for multiple destination networks is considered. The minimum time rather than total delay cost functional is employed. The problem is solved through an iterative link-by-link optimization. Each link capacity is optimally partitioned by examining the upper bounds for the evacuation time imposed through different capacity allocations for each origin/destination pair traffic. The computational complexity per iteration is polynomial in the number of network nodes. This is due to the examination of origin/destination pairs rather then destinations alone as in previous work where a similar approach led to exponential complexity. Sufficient conditions for the convergence of the iterative algorithm to the optimum are given. If these are not satisfied supplementary steps are described which conduct the algorithm to the desired solution. These involve exponential computational complexity.>

The asynchronous transfer mode (ATM) adaptation layer provides functions for mapping source traffic into ATM cells as required in recent standardization work for packet switched integrated broadband networks. Functions, services, and protocols suitable for signaling and other packet mode traffic are studied. The resulting protocol stacks are critically examined for two important and differing applications: signaling in broadband ISDN and the IEEE 802.3-5 series of standards for LAN interconnection. The emphasis is on the second case, which is currently considered as an imminent application area for broadband communication networks.>

The dynamic routing problem with multiple destinations on ring networks is examined. The authors discuss the peculiarities of the ring topology as well as the resulting simplification for the dynamic routing problem. The problem is transformed into a problem that minimizes link evacuation times. It involves a minimax cost and is equivalent to a linear program admitting a finite solution. A different approach is then taken: a solution based on an infinite algorithm is proposed and used to obtain a complexity of only O( mod N mod /sup 3/) per iteration and an exponential rate of convergence to the minimal value. Several optimal routing policies are characterized and formulated. It is found that the store-and-forward feature is not necessary in order to implement a particular optimal routing. Optimality can be achieved by a relatively simple protocol reminiscent of accessing procedures in local area networks. The incorporation of external arrival rates is discussed. Examples are worked out, and suggestions for future work are given.>

The dynamic routing problem for multiple destination networks is considered. The minimum time rather than total delay cost functional is employed. Each link capacity is optimally partitioned by examining the competition of bottlenecks associated with each destination. The multidestination problem is thus solved through an iterative link-by-link optimization.

We present an algorithm for optimal routing in communication networks, resulting in minimum time and minimum total delay clearing of congested traffic towards a single destination. The algorithm is suitable for on-line implementation and can also be applied in the presence of time constant external arrival rates. In the case where several optimal solutions exist, the solution given is of the simplest form. The results are discussed and compared to existing ones, in particular to optimal feedback solutions found in the literature. The simplicity of approach and results allows us to give necessary and sufficient conditions for arrival rates, so that the minimal value for the maximal delay encountered by any packet in the network does not increase when these external arrivals are present. This suggests a flow control policy which, together with optimal routing, gives a guaranteed upper limit for traffic delay, while inhibiting incoming traffic as little as necessary. A thorough geometric interpretation is given and examples illustrate the applicability of results.