Interworking Methodologies for DCOM and CORBA.

The DCOM and CORBA standards provide location-transparent access to network-resident software through language independent object interfaces. Although the two standards address similar problems, they do so in incompatible ways: DCOM clients cannot use CORBA objects, and CORBA clients cannot utilize DCOM objects, due to incompatible object system infrastructures. This thesis investigates the performance of bridging tools to resolve the incompatibilities between DCOM and CORBA, in ways that allow clients to cross object system boundaries. Two kinds of tools were constructed and studied: tools that bind clients to services at compile time, and tools that support dynamic client-server bindings. Data developed in the thesis shows that static bridges are on the order of five times faster than dynamic bridges. Measurements conducted with remote clients also showed that with increased network delays, performance differences between static and dynamic bridges become negligible

Protocols versus objects: can models for telecommunications and distributed processing coexist?

This paper identifies two paradigms that influence the design of telematics systems nowadays: the protocol-centred and the object-centred paradigms. Both paradigms have been introduced to cope with interoperability, each in their own way. The coexistence of these paradigms can have an enormous impact on the design of telematics systems. This paper identifies some combined uses of both paradigms and some fundamental research problems related to the coexistence of these paradigm

Performance of distributed information systems

There is an increasing use of distributed computer systems to provide services in both traditional telephony as well as in the Internet. Two main technologies are Distributed Object Computing (DOC) and Web based services. One common DOC architecture investigated in this thesis is the Common Object Request Broker Architecture (CORBA), specified by the Object Management Group. CORBA applications consist of interacting software components called objects. Two other DOC architectures investigated are the Telecommunications Information Net- working Architecture (TINA) and a CORBA based Intelligent Network (IN/CORBA) system. In a DOC environment, the objects of an application are distributed on mul- tiple nodes. A middleware layer makes the distribution transparent to the application. However, the distributed nature creates a number of potential performance problems. Three problems in DOC systems are examined in this thesis: object distribution, load balancing and overload protection. An object distribution describes how objects are distributed in the network. The objective is to distribute the objects on the physical nodes in such a way that intern-node communication overhead is as small as possible. One way to solve the object distribution problem is to use linear programming. The constraints for the problem are then given by both ease of management of the system and performance concerns. Load balancing is used when there are multiple objects that can be used at a particular time. The objective of load balancing is to distribute the load e±ciently on the available nodes. This thesis investigates a number of de- centralized load balancing mechanisms, including one based on the use of intelligent agents. Finally, overload protection mechanisms for DOC systems are investigated. While overload protection is well-researched for telecom networks, only little work has been performed previously concerning DOC and overload protection. Also, this thesis examines the use of overload protection in e-commerce web servers. Two schemes are compared, one which handles admission to the e-commerce site on request basis, and another which handles admission on session basis. The session based mechanism is shown to be better in terms of user-experienced performance

Adaptive object management for distributed systems

This thesis describes an architecture supporting the management of pluggable software components and evaluates it against the requirement for an enterprise integration platform for the manufacturing and petrochemical industries. In a distributed environment, we need mechanisms to manage objects and their interactions. At the least, we must be able to create objects in different processes on different nodes; we must be able to link them together so that they can pass messages to each other across the network; and we must deliver their messages in a timely and reliable manner. Object based environments which support these services already exist, for example ANSAware(ANSA, 1989), DEC's Objectbroker(ACA,1992), Iona's Orbix(Orbix,1994)Yet such environments provide limited support for composing applications from pluggable components. Pluggability is the ability to install and configure a component into an environment dynamically when the component is used, without specifying static dependencies between components when they are produced. Pluggability is supported to a degree by dynamic binding. Components may be programmed to import references to other components and to explore their interfaces at runtime, without using static type dependencies. Yet thus overloads the component with the responsibility to explore bindings. What is still generally missing is an efficient general-purpose binding model for managing bindings between independently produced components. In addition, existing environments provide no clear strategy for dealing with fine grained objects. The overhead of runtime binding and remote messaging will severely reduce performance where there are a lot of objects with complex patterns of interaction. We need an adaptive approach to managing configurations of pluggable components according to the needs and constraints of the environment. Management is made difficult by embedding bindings in component implementations and by relying on strong typing as the only means of verifying and validating bindings. To solve these problems we have built a set of configuration tools on top of an existing distributed support environment. Specification tools facilitate the construction of independent pluggable components. Visual composition tools facilitate the configuration of components into applications and the verification of composite behaviours. A configuration model is constructed which maintains the environmental state. Adaptive management is made possible by changing the management policy according to this state. Such policy changes affect the location of objects, their bindings, and the choice of messaging system

A framework for abstracting complexities in service delivery platforms

The telecommunication (telco) and Information Technology (IT) industries are converging into a single highly competitive market, where service diversity is the critical success factor. To provide diverse services, the telco network operator must evolve the traditional voice service centric network into a generic service centric network. An appropriate, but incomplete, architecture for this purpose is the Service Delivery Platform (SDP). The SDP represents an IT-based system that simplifies access to telco capabilities using services. SDP services offer technology independent interfaces to external entities. The SDP has vendor-specific interpretations that mix standards-based and proprietary interfaces to satisfy specific requirements. In addition, SDP architectural representations are technology-specific. To be widely adopted the SDP must provide standardised interfaces. This work contributes toward SDP standardisation by defining a technology independent and extendable architecture, called the SDP Framework. To define the framework we first describe telecom-IT convergence and a strategy to manage infrastructure integration. Second, we provide background on the SDP and its current limitations. Third, we treat the SDP as a complex system and determine a viewpoint methodology to define its framework. Fourth, we apply viewpoints by extracting concepts and abstractions from various standard-based telecom and IT technologies: the Intelligent Network (IN), Telecommunication Information Networking Architecture (TINA), Parlay, enhanced Telecommunications Operations Map (eTOM), Service Oriented Architecture (SOA) and Internet Protocol Multimedia Subsystem (IMS). Fifth, by extending the concepts and abstractions we define the SDP framework. The framework is based on a generic business model and reference model. The business model shows relationships between SDP, telco and external entities using business relationships points. The reference model extends the business model by formalising relationships as reference points. Reference points expand into interfaces exposed by services. Applications orchestrate service functions via their interfaces. Service and application distribution is abstracted by middleware that operates across business model domains. Services, interfaces, applications and middleware are managed in Generic Service Oriented Architectures (GSOA). Multiple layered GSOAs structure the SDP framework. Last, we implement the SDP framework using standard-based technologies with open service interfaces. The implementation proves framework concepts, promotes SDP standardisation and identifies research areas

Realizing mobile multimedia systems over emerging fourth-generation wireless technologies

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2001.Includes bibliographical references (p. [161]-167) and index.by Pei-Jeng Kuo.M.Eng

A distributed intelligent network based on CORBA and SCTP

The telecommunications services marketplace is undergoing radical change due to the rapid convergence and evolution of telecommunications and computing technologies. Traditionally telecommunications service providers’ ability to deliver network services has been through Intelligent Network (IN) platforms. The IN may be characterised as envisioning centralised processing of distributed service requests from a limited number of quasi-proprietary nodes with inflexible connections to the network management system and third party networks. The nodes are inter-linked by the operator’s highly reliable but expensive SS.7 network. To leverage this technology as the core of new multi-media services several key technical challenges must be overcome. These include: integration of the IN with new technologies for service delivery, enhanced integration with network management services, enabling third party service providers and reducing operating costs by using more general-purpose computing and networking equipment. In this thesis we present a general architecture that defines the framework and techniques required to realise an open, flexible, middleware (CORBA)-based distributed intelligent network (DIN). This extensible architecture naturally encapsulates the full range of traditional service network technologies, for example IN (fixed network), GSM-MAP and CAMEL. Fundamental to this architecture are mechanisms for inter-working with the existing IN infrastructure, to enable gradual migration within a domain and inter-working between IN and DIN domains. The DIN architecture compliments current research on third party service provision, service management and integration Internet-based servers. Given the dependence of such a distributed service platform on the transport network that links computational nodes, this thesis also includes a detailed study of the emergent IP-based telecommunications transport protocol of choice, Stream Control Transmission Protocol (SCTP). In order to comply with the rigorous performance constraints of this domain, prototyping, simulation and analytic modelling of the DIN based on SCTP have been carried out. This includes the first detailed analysis of the operation of SCTP congestion controls under a variety of network conditions leading to a number of suggested improvements in the operation of the protocol. Finally we describe a new analytic framework for dimensioning networks with competing multi-homed SCTP flows in a DIN. This framework can be used for any multi-homed SCTP network e.g. one transporting SIP or HTTP

FIPA-Compliance of HTML5 Agent Framework

In agent-oriented architecture, systems are built on autonomous components called agents. Agents exist and operate in an agent environment/platform. When an agent environment contains two or more agents, it is called Multi-agent System (MAS). Like humans, agents have an ability to cooperate, coordinate, negotiate and interact with each other to resolve problems on the behalf of their users. Moreover, agents in agent environment can reach beyond its system environment and interact with agents in other third-party agent environments for co-operative problem solving. Agent systems developed by different developers possess architecture specific features and implementation. These differences among agent systems prevent interoperability between agents existing in different agent environment. Therefore, mechanisms that allow agents and/or MASs to interoperate are needed. It is easier to rationalize the use of agent systems based on existing well known standards like FIPA than on self-made standards. The HTML5 Agent Framework developed in TUT has its own architecture specific features and implementation. The main purpose of this thesis is to analyze how HTML5 Agent Framework can be made FIPA compliant. An agent system that conforms to FIPA specifications is a FIPA-compliant system. A FIPA-compliant system can interoperate with other heterogeneous agent systems that are FIPA-compliant as well. The conversion of MAS into a FIPA-compliant system is one way of guaranteeing interoperability between different MASs. FIPA is a standard body that provides specifications for developers of agent systems. It promotes agent-based technologies and interoperability of its standards with other agent-based technologies that facilitate the end-to-end interworking of agent systems in modern commercial and industrial settings. In this thesis, the current implementation of HTML5 Agent Framework is mapped with FIPA standards. This thesis presents analysis to make HTML5 Agent Framework a FIPA-compliant agent system. Moreover, possible solutions to make HTML5 Agent Framework compliant to FIPA are suggested. A proof of concept is also implemented. It can establish simple communication between HTML5 agent and FIPA-compliant JADE agent