A single programming model is provided for accessing a plurality of distinct message transports while developing one or more applications for message delivery between two endpoints. The programming model allows for independently configurable assurances and features for transporting the messages. The configurable assurances may be selected from at least once delivery, at most once message delivery, in order message delivery, and message time to live. The independently chosen features may include a session state storage, an extension of time to live, and transacted message buffering.

Message delivery with configurable assurances and features between two endpoints

Suitable pricing models for Internet services represent one of the main prerequisites for a successfully running implementation of a charging and accounting system. This paper introduces general aspects influencing the choice of a pricing model in practical situations and presents a survey as well as a classification of relevant and advanced approaches to be found in the scientific literature. First performance results on charging extensions within the Internet are presented, which are completed by a set of market price simulations for dynamic pricing models within the same implementation environment. Based on cost model investigations some detailed insights into price and cost issues from an Internet Service Provider's (ISP) point of view are given. Moreover, current challenges as well as problems are discussed in a practical context as investigated in the Swiss National Science Foundation project Charging and Accounting Technology for the Internet (CATI).

Pricing and Cost Recovery for Internet Services: Practical Review, Classification, and Application of Relevant Models

Conference control has been an area of intensive research over the years but widely accepted robust and scalable solutions and standards are still lacking. The main conference control components are conference management and floor (resource) control. We identify the requirements for conference control and propose a component-based scalable conference control framework employing the Session Initiation Protocol (SIP) and the Simple Object Access Protocol (SOAP). The framework assumes a single control point, but our architecture can scale to large groups by distributing media via a tree-shaped hierarchy of conference servers.

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A SIP-based conference control framework

Various embodiments of systems, methods, and computer programs are disclosed for authenticating a participant in an online conference via a graphical user interface. One such method comprises: determining a conference event requesting authentication of a participant by a conferencing system hosting a conference via a communication network; in response to the conference event, presenting a signature capture area to the participant in a conference interface via a graphical user interface; monitoring location coordinates of an input device in the signature capture area; converting the location coordinates into a participant electronic signature; determining that the participant electronic signature matches a stored electronic signature associated with the participant; and in response to determining the match, authenticating the participant for the conference event.

Participant authentication via a conference user interface

There are currently two standards for signaling and control of Internet telephone calls, namely ITU-T Recommendation H.323 and the IETF Session Initiation Protocol (SIP). We describe how an interworking function (IWF) can allow SIP user agents to call H.323 terminals and vice versa. Our solution addresses user registration, call sequence mapping and session description. We also describe and compare various approaches for multi-party conferencing and call tranfer.

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Interworking Between SIP/SDP and H.323

A chargeable session on the Internet may consist of more than one underlying chargeable service. Typically there will be two, one at the network layer and one at the session layer. Since different applications can have different demands from the Network, a generic charging scheme has to separate the service provided by the network from the service provided by an application/service provider. In this paper we propose a pricing model which is session based and we look at the impact of this on real-time multimedia conferencing over the Internet. In this model, we are trying to allow for the optional integration of charging at the network layer with charging at the session layer, while keeping the underlying technologies still cleanly apart. This paper also highlights the fact that the main problem of pricing application on the Internet is not just a simple case of analyzing the most technically feasible pricing mechanism but also making the solution acceptable to users. We take the position that session based pricing is easier for end users to accept and understand and show why this is the case in this paper.

A Charging Model for Sessions on the Internet

Conference control is an integral part in many-to-many communications that is used to manage and co-ordinate multiple users in conferences. There are different types of conferences which require different types of control. Some of the features of conference control may be user invoked while others are for internal management of a conference. In recent years, ITU (International Telecommunication Union) and IETF (Internet Engineering Task Force) have standardized two main models of conferencing, each system providing a set of conference control functionalities that are not easily provided in the other one. This paper analyzes the main activities appropriate for different types of conferences and presents an architecture for conference control called GCCP (Generic Conference Control Protocol). GCCP interworks different types of conferencing and provides a set of conference control functions that can be invoked by users directly. As an example of interworking, interoperation of IETF's SIP and ITU's H.323 call control functions have been examined here. This paper shows that a careful analysis of a conferencing architecture can provide a set of control functions essential for any group communication model that can be extensible if needed.

Architecture of conference control functions

Multi-party collaborative multimedia applications require data to be transmitted reliably and efficiently in order to provide a guaranteed quality of service (QoS). The multimedia applications can vary from distributed games and shared whiteboards to interactive video conferencing. These applications often involve a large number of participants and are interactive in nature, with participants dynamically joining and leaving the applications. In order to provide many-to-many interaction when the number of participants is large, IP multicasting is a very good option for communication. IP multicasting provides scalability and efficient routing but does not provide the reliability that these multimedia applications may require. Though a lot of research has been done on reliable multicast transport protocols, it really seems that the only way of doing a reliable multicast is to build it for a given purpose like conference control in multimedia conferencing. This paper compares some of the available multicast transport protocols and analyses the most suitable features and functionalities provided by these protocols for a facet of conference control: floor control. The goal is to find or design a reliable multicast transport protocol which would scale to tens or hundreds of participants scattered across the Internet and which would deliver the control messages reliably.

End to end reliable multicast transport protocol requirements for collaborative multimedia systems

This paper describes a protocol by which people communicating using different conference control mechanisms can be seamlessly integrated into a single conference control mechanism. A generic approach to conference control, General Conference Control Protocol (GCCP) is proposed to support and bind formal/tightly coupled multimedia conference (ITU standardised) with the informal/loosely coupled conference (IETF based). These two types of conferences are used by two different types of community and the innate differences in the underlying architecturc of IETF and ITU based conferencing makes it difficult to interoperate. The differences and the similarities of these two architectures are explored and a protocol is proposed in this paper which will interoperate between two different types of conferences. A single generic conference control system covers a range of services provided by different conference controls. Participants in different kind of conferencing with different kind of underlying architecture can use a particular type of service(s) from generic conference control which will integrate them into a single mechanism. The appropriate and relevant features of existing conference control mechanisms have been used to design a tool for conference management.

General conference control protocol

In order to provide guaranteed QoS multiparty collaborative multimedia applications require reliable transmission of data. The multimedia applications can vary from distributed games, shared whiteboard to interactive video conferencing. These applications often involve a large number of participants and are interactive in nature with participants dynamically joining and leaving the applications[Sudan95]. In order to provide many-to-many interaction when the number of participants is large IP multicast is a very good option for communication. IP multicast provides scalability and efficient routing but does not provide the reliability these multimedia applications may require. Though a lot of research has been done on reliable multicast transport protocol, it really seems that the only way of doing a reliable multicast is to build it for a given purpose like conference control in multimedia conferencing.

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Nadia Kausar

Papers

A Charging Model for Sessions on the Internet

Architecture of conference control functions

End to end reliable multicast transport protocol requirements for collaborative multimedia systems

General conference control protocol

End-to-End Reliable Multicast Transport Protocol Adaptation for Floor Control and Other Conference Control Functions Requirements