Maarten Wegdam

Transparent dynamic reconfiguration for CORBA

Distributed systems with high availability requirements have to support some form of dynamic reconfiguration. This means that they must provide the ability to be maintained or upgraded without being taken off-line. Building a distributed system that allows dynamic reconfiguration is very intrusive to the overall design of the system, and generally requires special skills from both the client and server side application developers. There is an opportunity to provide support for dynamic reconfiguration at the object middleware level of distributed systems, and create a dynamic reconfiguration transparency to application developers. We propose a Dynamic Reconfiguration Service for CORBA that allows the reconfiguration of a running system with maximum transparency for both client and server side developers. We describe the architecture, a prototype implementation, and some preliminary test results.

Extending CORBA with specialised protocols for QoS provisioning

The CORBA layer in a distributed system hides the heterogeneity of the underlying computer network. The interactions of objects located at different computing systems are described in terms of IDL specifications and the ORB takes care of the actual transfer of messages along the wire. In fact, an object interaction is translated into the transfer of GIOP messages over TCP/IP networks (IIOP). The advantages in terms of interoperability and portability are obvious. Currently, OMG is in the process of standardising the Open Communication Interface (OCI). Through OCI, a protocol module can be plugged into any ORB and hence, the distributed application including the ORB can be put on top of any network without changing the applications code, thus implementing network transparency. Obviously, the QoS of distributed applications depends on the QoS of the underlying network protocols e.g., best effort versus guaranteed bandwidth. Through OCI we are able to use the network protocol that is needed to satisfy the QoS requirements of a specific distributed application. We propose to extend CORBA with specialised protocols for QoS provisioning using OCI. We have prototyped protocol plug-ins, including a plug-in that exploits IP Multicast. The IP Multicast plug-in can be used in situations where one client communicates with a group of replicated servers. We have used this mechanism to implement replication transparency in CORBA and have shown that the OCI interface can be used for QoS provisioning in CORBA. Based on our hands-on experience, we have also identified some shortcomings in the proposed OCI specification.

Value added Web: integrating WWW with a TINA service management platform

One of the most spectacular developments of this decade is the enormous growth of the Internet. One of the most popular services of the Internet is the World Wide Web (WWW). It may be expected that the Web will be used to provide more sophisticated services, e.g., video on demand. Customers will be prepared to pay for such services, because of the exclusive content and the quality of the (broadband) transport network needed to transfer the information. Consequently, we need a way to manage these services, without violating the ease of use provided by current WWW. In this paper we present a solution based on TINAs business model. We introduce the value added Web (VAW), which is an integration of the WWW with TINA service management. This combination adds the benefits of the TINA business model to the WWW. A VAW session appears as a normal WWW session, except that it allows charging for specific content and the setup of connections with an agreed quality of service. The VAW business model assumes that users only have a direct relation with a retailer and that the retailer is responsible for charging. This paper describes the rationale behind VAW and the design and implementation of a prototype of VAW.

Web services in third-generation service platforms

In third-generation (3G) networks, third-party service developers will have access to the mobile network resources using open network interfaces, such as the 3rd Generation Partnership Projects (3GPPs) Open Service Access (OSA). The service platforms that offer these interfaces provide interoperability, third-party access, and ease of use, which goes beyond the capabilities of existing intelligent network technologies. OSA is usually implemented using CORBA∗ object middleware. To accommodate a broad community of developers and scenarios of deployment, middleware technologies other than CORBA should be supported as well. In this paper we discuss Web services, an emerging Extensible Markup Language (XML)-based middleware technology that is especially targeted at the Internet community. We describe the technical benefits of both Web services and CORBA in an OSA context and look at the main issues and possible solutions with respect to offering Web services-based access to the OSA interfaces. We also describe a prototype to validate our conclusions.

Using Message Reflection in a Management Architecture for CORBA

The availability of object middleware, such as CORBA, is rapidly being accepted as a means for cost effective and fast development for a wide range of distributed applications. Distributed applications that are built using these technologies often comprise many objects and become more and more complex. The deployment of such large distributed applications requires a significant improvement of management methods and tools. In this paper, we present a management architecture for object middleware based systems. We use message reflection to extend the middleware layer with management capabilities, i.e. we monitor the application by observing the messages exchanged between the objects of the distributed application. We argue why management should be transparent to the application developer and show that message reflection supports this management transparency. We have compared different mechanisms to implement message reflection in CORBA, and argue why portable interceptors are the most suitable. Finally, we describe our prototype and the lessons we learned.

An Architecture for User Location in Heterogeneous Mobile Networks

Fourth generation mobile networks will allow end-users to roam over different network technologies, such as UMTS, CDMA2000 and Wi-Fi. These mobile networks make it possible to determine the location of the mobile terminal, which can be used by applications to provide enhanced services. Each mobile network technology has its specific way to determine the terminal’s location, and to provide this information to the end-user or mobile application. Mobile application developers should not be exposed to the peculiarities of the different network technologies, and should be offered a network technology independent API to obtain user location information. In this paper we propose an architecture that provides 3rd party mobile application developers with a secure API to obtain the user’s location over heterogeneous networks that are managed by different parties. The proposed architecture is validated by a proof- of-concept implementation using UMTS and Wi-Fi networks.

Validation of the Open Service Access API for UMTS Application Provisioning

UMTS networks will allow the deployment of new types of applications, that are rich, interactive and multimedia capable, because of increased bandwidth, richer devices and location awareness. These applications are not necessarily provided by the network operator, but can be created and deployed by any third party. However, these third parties will need access to the UMTS core network capabilities, especially when it comes to call related services, location based services and services that charge for certain content. Intelligent Network (IN) based service creation and delivery platforms deployed in current 2G and 2.5G networks do not offer suitable interfaces for this, since third parties need to have detailed knowledge and expertise of low level, telecommunication specific protocols and can jeopardize the integrity of the network. The recent activities within the standardization bodies 3GPP and ETSI SPAN, and the industry forums Parlay and JAIN show an increased interest in the area of open network Application Programming Interfaces (APIs). The Open Service Access (OSA) specification is a collection of open network APIs for UMTS application provisioning defined by 3GPP. OSA is meant to allow third party application development and deployment by means of open, secure, and standardized access to core network capabilities, while preserving the integrity of the underlying network. We describe a prototype implementation, and list the possibilities and limitations of the OSA specification.

Trust management support for context-aware service platforms

High quality context information retrieved from trustworthy context providers allows a more reliable context-aware service adaption but also implies a higher risk for the service users in case of privacy violations. In this chapter we present a trust management model that support users and providers of context-aware services in managing the trade-off between privacy protection and context-based service adaptation. We applied our trust management model in two trust-based selection mechanisms. The first trust-based selection mechanism support users of context-aware services in selecting trustworthy service providers to interact with. This mechanism supports the users in the selection process, taking into account the users’ goals, trust beliefs, and the trust dependencies between the service users and the entities that collaborate in the context-aware service provisioning. The second trust-based selection mechanism supports context-aware service providers in selecting trustworthy context providers taking into account the trustworthiness of the context providers to provide context information about a specific user and quality level. To conclude this chapter we present the evaluation of the technical feasibility of our trustmanagement model in trust-based selection mechanisms through a prototype implementation.

Audio/Video Stream Binding in a Pan-European Service Management Platform

The ability to carry stream information over a range of network types in a managed way will become an essential requirement for telecommunication network operators as future services evolve to include the transmission of audio/video and bulk data streams. This paper details the architecture of a working pan-European demonstrator offering multimedia services through the integration of stream control, as specified in OMGs Control & Management of Audio/Video Streams, with a TINA-compliant service management environment. This CORBA-based demonstrator, known as the EURESCOM Services Platform (ESP), has been developed by six European telecommunication companies within EURESCOM project P715. Various modelling concepts, as defined by TINA, ODP and OMG, have been used and verified in a first prototype implementation, with connectivity provided by commercially available multimedia technology such as H.320/323 products. This EURESCOM Services Platform prototype is one of the first demonstrators world-wide to implement OMGs Control & Management of A/V Streams specification.