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No description available.

No description available.

No description available.

No description available.

Recent advances in the area of computer networking have led to a number of approaches to providing multi-service networks. Of particular importance are B-ISDN & ATM on the one hand, and the Internet, based on IP, on the other. The idea that the coupling of B-ISDN and ATM would provide the global solution for the wide-scale deployment of broadband telecommunications has been strongly challenged by the Internet and its associated protocols. What now exists is a multi-service scenario where distributed multimedia applications with a variety of requirements will be supported across multiple heterogeneous networks, encompassing B-ISDN/ATM and IP as well as other local access and core networking technologies. This thesis introduces Open Network Control as a means to integrate the variety of communication services and platforms that will continue to co-exist. A key starting point is the area of broadband network control, which has seen a number of projects looking at open control mechanisms, using a combination of low-level interfaces onto network devices and the use of middleware technology to provide the control interaction between these devices. In the thesis, the need is argued for a generic level of network control that allows for the support of different network services and different control mechanisms in a uniform and consistent manner. This begins with a critical examination of the approaches to providing multi-service networks that are currently dominant within the networking community, highlighting where each may be claimed as "fit for purpose". A middleware-based Open Network Control architecture and signalling mechanism is then presented, based around a set of strictly defined requirements. Support for continuous media interaction abstractions, a model for the definition of application requirements and a distributed connection binding technique contribute to an overall architecture of Open Network Control. Finally, an evaluation of the architecture is made through a series of measurements based around a real-life application. Performance is considered both in terms of timing characteristics and in terms of the overhead of control messaging within different elements of the architecture.

While computer networks have been of low capacity or poor reliability, their use for real-time communications for human interaction was considered infeasible on any large scale, since audio and video data consumed vast amounts of memory and processing capacity. However, recent and forthcoming enhancements to network quality, along with advanced compression algorithms, falling costs of memory and fast processors, have allowed such applications to develop, as well as protocols to support them. On top of this, global interconnectivity of local networks has improved, giving scope to expand human communications applications to wide areas, and with many participants. Such group communication applications have various networking Quality of Service (QoS) demands, such as lower bandwidth but high reliability. The mahor challenge in multimedia group communications is therefore about developing network services to support group communications with varying QoS, in order to allow groups of people, potentially very widely distributed around the world, to interact through computers of varying abilities, using combinations of media such as video, audio, and shared editing of documents. The Media Channel (MC) model is an attempt to unify the control and management of applications of different media types. It provides common group management facilities for all types of application, and allows participation in an application to be expressed simply as contribution (using a source) and/or observation (using a sink). This further allows a multimedia group application to be built up from several ‘unimedia’ group applications (the ‘channels’) through the use of a user agent which manages and simplifies a user’s participation in several applications. Participation in multimedia group applications (or ‘sessions’) can then be configured automatically for several users by describing the channels of the session to each involved user agent. The description itself can be supplied through a channel, with the agents acting as sinks. The user can control participation in all the channels of the session by (de)activating the agent’s session sink, and while joined, session administrators can inform all session participants of new channels to which they are invited. The MC model's main shortfall is its use of a central manager — an architecture which does not scale well to many participants, and which may lead to uneven management for widely distributed participants, particularly as group populations migrate. This thesis considers the issues of multimedia group communication, and attempts to realise the MC model. Some earlier definitions of the MC model are refined in the present thesis, and alternative architectures are designed, implemented and evaluated. These new architectures allow the management components of a media channel to be placed near to the participants, and then to migrate as participants leave the components’ areas, and as new ones join in others. At the same time, management information to evaluate policies is compressed and distributed among components. The model is also extended to allow sources to describe their data arbitrarily, enabling sinks to accept or reject them individually depending on availability of local resources.

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Virtual Environments (VEs) attempt to give people the illusion of immersion that they are in a computer generated world. VEs allow people to actively participate in a synthetic environment. They range from a single-person running on a single computer, to multiple-people running on several computers connected through a network. When VEs are distributed on multiple computers across a network, we call this a Distributed Virtual Environment (DVE). Virtual Environments can benefit greatly from distributed strategies. A networked VE system based on the Client-Server model is the most commonly used paradigm in constructing DVE systems. In a Client-Server model, data can be distributed on several server computers. The server computers provide services to their own clients via networks. In some client-server models, however, a powerful server is required, or it will become a bottleneck. To reduce the amount of data and traffic maintained by a single server, the servers themselves can be distributed, and the virtual environment can be divided over a network of servers. The system described in this thesis, therefore, is based on the client-server model with multiple servers. This grouping is called a Distributed Virtual Environment System with Multiple- Servers (DVM). A DVM system shows a new paradigm of distributed virtual environments based on shared 3D synthetic environments. A variety of network elements are required to support large scale DVM systems. The network is currently the most constrained resource of the DVM system. Development of networking architectures is the key to solving the DVM challenge. Therefore, a networking architecture for implementing a DVM model is proposed. Finally, a DVM prototype system is described to demonstrate the validity of the modelling and network architecture of a DVM model.

With the globalisation and constant changes in the marketplace, enterprises are adapting themselves to face new challenges. Therefore, strategic corporate alliances to share knowledge, expertise and resources represent an advantage in an increasing competitive world. This has led the integration of companies, customers, suppliers and partners using networked environments. This thesis presents three novel solutions in the tooling area, developed for Seco tools Ltd, UK. These approaches implement a proposed distributed computing architecture using Internet technologies to assist geographically dispersed tooling engineers in process planning tasks. The systems are summarised as follows. TTS is a Web-based system to support engineers and technical staff in the task of providing technical advice to clients. Seco sales engineers access the system from remote machining sites and submit/retrieve/update the required tooling data located in databases at the company headquarters. The communication platform used for this system provides an effective mechanism to share information nationwide. This system implements efficient methods, such as data relaxation techniques, confidence score and importance levels of attributes, to help the user in finding the closest solutions when specific requirements are not fully matched In the database. Cluster-F has been developed to assist engineers and clients in the assessment of cutting parameters for the tooling process. In this approach the Internet acts as a vehicle to transport the data between users and the database. Cluster-F is a KD approach that makes use of clustering and fuzzy set techniques. The novel proposal In this system is the implementation of fuzzy set concepts to obtain the proximity matrix that will lead the classification of the data. Then hierarchical clustering methods are applied on these data to link the closest objects. A general KD methodology applying rough set concepts Is proposed In this research. This covers aspects of data redundancy, Identification of relevant attributes, detection of data inconsistency, and generation of knowledge rules. R-sets, the third proposed solution, has been developed using this KD methodology. This system evaluates the variables of the tooling database to analyse known and unknown relationships in the data generated after the execution of technical trials. The aim is to discover cause-effect patterns from selected attributes contained In the database. A fourth system was also developed. It is called DBManager and was conceived to administrate the systems users accounts, sales engineers’ accounts and tool trial monitoring process of the data. This supports the implementation of the proposed distributed architecture and the maintenance of the users' accounts for the access restrictions to the system running under this architecture.