Kausar, Nadia; (2000) A framework for conference control functions. Doctoral thesis (Ph.D.), University College London (United Kingdom).

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Abstract

Conference control is an integral part in one-to-many communications that is used to manage and co-ordinate multiple users in different conferences. The degree which it controls the interaction of participants can vary in accordance with the conference structure in use. Conferences come in different shapes and formats but in recent years the two different views of conference control has been realised by two prominent standard bodies: International Telecommunication Union (ITU) and the Internet Engineering task Force (IETF). The former has focused on the centralised control of conferences (formal/tightly coupled). Whereas the IETF approach is referred as the informal/loosely coupled conference. However, in addition there are other conference controls for desktop multimedia system that are not yet standardised. In this thesis the writer proposes a generic conference control system to provide a single mechanism that supports interoperability between two or more inherently different architectures mentioned above. The consequence of having very distinctive systems is that they are not interoperable. Each system provides a set of functionalities that are not easily provided in the other one. Users or administrators of such systems end up supporting dual stack technologies. However, both the systems have some common components like a call control and media part. In this research, one of the key tasks performed was to interwork two innate different architectures using their common call control functions. Also, a set of conference control functions have been derived and implemented that can be used by any conferencing systems over heterogeneous networks. The architecture that provides a set of functions and requirements that are visible or invisible to any user in any type of conferencing is termed as CCCS (Common Conference Control services) in this thesis. In order to evaluate the integration of different services offered by different conference control model, IETF's Session Initiation Protocol (SIP) and ITU's H323 conferencing have been interoperated in an implementation. It has been established that conferees from completely different architectures can participate in one session by a mechanism such as CCCS which interoperates a set of services that are common in any conferencing systems. These common services have been derived by careful analysis, and with the aid of formal methods, state transition diagrams and a well-known software design pattern. The CCCS framework presented in this thesis provides the flexibility to users which are not present in just one of the architectures alone. This thesis performs three key tasks: a) a detailed analysis of the activities appropriate for different types of sessions, and the common set of functions required to interwork them b) the transport level requirements to make these set of conference control functionalities reliable and scalable (in this case IP multicast have been studied) c) an effective solution to show extendibility afforded by the framework to charge conferences from the session layer. CCCS, designed with these functions have been tested to work over unreliable networks like the Internet and is used to draw some general guidelines for the design of such systems.

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