Distributed Multimedia Applications Research Articles

CRAM: Cell Re-labeling At Merge-points for ATM multicast

Many distributed multimedia applications involve data delivery from a source to multiple destinations, the participating nodes forming a multicast group. In the naive solution, separate connections can be established from each source to other group members. However, a tree can be established for each source with the participants as the leaf nodes or just have one tree spanning all the participants. In this paper, we introduce a data forwarding model to support such shared multicast trees over the ATM networks called CRAM (Cell Re-labeling At Merge-points for ATM multicast). Our work allows VC merging in the MPLS architecture and supports recently proposed wide area multicast protocols (like CBT and PIM) in ATM networks.

A distributed delay-constrained dynamic multicast routing algorithm

Many new distributed multimedia applications involve dynamic multiple participants, have stringent end-to-end delay requirement and consume large amount of network resources. In this paper, we propose a distributed delay-constrained dynamic multicast routing algorithm (DCDMR) to support these applications. DCDMR scales well because the source of the multicast tree needs only limited computation or may even not be involved in the route computation. When group membership changes, the existing multicast tree is perturbed as little as possible and the resulting tree cost performance is very satisfactory.

A control-based middleware framework for quality-of-service adaptations

In heterogeneous environments with performance variations present, multiple applications compete for and share a limited amount of system resources and suffer from variations in resource availability. These complex applications are desired to adapt themselves and to adjust their resource demands dynamically. On one hand, current adaptation mechanisms built within an application cannot preserve global properties such as fairness; on the other hand, adaptive resource management mechanisms built within the operating system are not aware of data semantics in the application. In this paper, we present a novel middleware control framework to enhance the effectiveness of quality-of-service (QoS) adaptation decisions by dynamic control and reconfiguration of internal parameters and functionalities of a distributed multimedia application. Our objective is to satisfy both system-wide properties (such as fairness among concurrent applications) and application-specific requirements (such as preserving the critical performance criteria). The framework is modeled by the task control model and the fuzzy control model, based on rigorous results from the control theory, and verified by the controllability and adaptivity of a distributed visual tracking application. The results show validation of the framework, i.e., critical application quality parameters can be preserved via controlled adaptation.

Design and implementation of a distributed multimedia collaborative environment

Multimedia applications are being developed and used for many aspects of our lives today. New high-speed, broadband networks have emerged and made the operation of these high-bandwidth requiring applications readily feasible. However, the development of distributed multimedia applications and efficient and reliable operation of these applications are still very difficult. This paper presents a flexible and reliable distributed multimedia collaborative environment called MAESTRO which provides a rich multimedia collaborative service API and which provides distributed multimedia services that can be used to develop a variety of multimedia applications easily. MAESTRO has been designed using CORBA. The system as well as applications running on it are managed and controlled in order to provide a reliable and efficient multimedia operations environment. We validate our claim by developing a number of multimedia applications using our distributed multimedia system and by using them for supporting distributed collaborative scientific and engineering research experiments.

An experimental study for transmitting MPEG-2 streams over ATM networks

This paper presents a comparative study of the different techniques aimed at transmitting MPEG-2 streams over ATM networks, with emphasis on the presentation of practical results achieved on an experimental platform available at LSI, a laboratory of the University of Sao Paulo, Brazil. This study determines some tuning parameters for optimizing the implementation of distributed multimedia applications on different network technologies. The focus of this experimental study has been on non native ATM techniques like "classical IP over ATM" and "LAN emulation", as well as native ATM techniques based on direct access service primitives to AAL 5. The influence of different parameters on the resulting throughput, like packet length, buffer size, CPU speed, has been studied. Furthermore, a testing tool is being developed for assessing the transmission of MPEG-2 streams based on the practical experience achieved so far. These results will permit the evaluation of different network technologies and also help in the development of distributed multimedia applications like video-on-demand, videoconferencing and telemedicine.

QoS-aware resource management for distributed multimedia applications

The ability of operating system and network infrastructure to provide end-to-end quality of service (QoS) guarantees in multimedia is a major acceptance factor for various distributed multimedia ap...

A user-centric view of QoS-aware communication

Recent technological advances coupled with new trends in using today's computing and communication infrastructure have raised new challenges in designing user interfaces for distributed multimedia applications. It has become essential to present the idea of QoS to the user, not only due to limitations of the infrastructure, but also because of the need to control user-machine interface bandwidth. In addition, a need for a tighter integration of communication and collaboration has become apparent. In this paper, we motivate the need for QoS support in the user-interface by considering shared virtual spaces, a unified communication paradigm for collaboration. We present a user-interface framework which provides the user with implicit and explicit control of quality of service, and describe our experience in designing and implementing such systems.

Quality-of-service adaptation in distributed multimedia applications

High-speed networks and powerful end-systems enable new types of applications, such as video-on-demand and teleconferencing. Such applications are very demanding on quality of service (QoS) because of the isochronous nature of the media they are using. To support these applications, QoS guarantees are required. However, even with service guarantees, violations may occur because of resources shortage, e.g., network congestion. In this paper we propose new adaptation approaches, which allow the system to recover automatically, if possible, from QoS violations (1) by identifying a new configuration of system components that might support the initially agreed QoS and by performing a user-transparent transition from the original configuration to the new one, (2) by redistributing the levels of QoS that should be supported, in the future, by the components, or (3) by redistributing the levels of QoS that should be supported immediately to meet end-to-end requirements based on the principle that (local) QoS violation at one component may be recovered immediately by the other components participating in the support of the requested service. The proposed approaches, together with suitable negotiation mechanisms, allow us (1) to reduce the probability of QoS violations which may be noticed by the user, and thus, to increase the user confidence in the service provider, and (2) to improve the utilization of the system resources, and thus to increase the system availability.

The usage of advance reservation mechanisms in distributed multimedia applications

Distributed multimedia applications impose specific requirements concerning quality-of-service. To satisfy these requirements, the reservation of network and end system resources is necessary. Particularly for applications with relatively long duration and significant importance from a business point of view, it is desirable to do such reservations well in advance of the actual run-time. This way, the probability of resource availability can be increased, and network utilisation can be improved. Based on our design and implementation of a mechanism for resource reservation in advance (ReRA), this paper describes the use of this approach within dedicated application scenarios. In particular, we both address videoconferencing based on the MBone tools and video-on-demand services based on extended client/server protocols. For these scenarios, reservation requirements are derived and typical design trade-offs concerning advance reservation mechanisms are discussed. From a practical point of view, the mapping of advance reservations onto either RSVP or onto direct ATM connections is outlined.

MANAGEMENT OF QUALITY OF SERVICE WITH SOFTWARE AGENTS

As distributed multimedia applications become more widely diffused, systems for quality of service QoS management are increasingly essential. In this paper we present an architecture for distributed QoS management based on software agents. We discuss the advantages of using agent technology in a problem inherently distributed and complex such as QoS management. Besides introducing several negotiation and coordination techniques among agents as fundamental properties for QoS management, it is argued in favor of decision making based on analytical and simulative modeling techniques. Furthermore, design and implementation issues are discussed in detail and our Java-based platform for agent-based QoS management is introduced.

A Scalable QoS-based inter-domain routing scheme in a high speed wide area network

In this paper we propose a scalable QoS-based inter-domain routing scheme for distributed multimedia applications in a high speed wide area network. The problem of QoS-based routing is formulated as a multicriteria shortest path problem, known as NP-complete [1,2] [W.C. Lee, M.G. Hluchyj, P.A. Humbler, Routing subject to quality of service constraints in integrated communication networks, IEEE Network (July/August 1995) 46–55. Z. Wang, J. Crowcroft, Quality of service routing for supporting multimedia applications, IEEE J. Select. Areas Commun. Special Issues on Multimedia Systems]. Our scheme consists of two phases. In Phase 1, we present a way of mapping the network into a graph that contains a part of the network topology which is neglected completely or partially by existing routing schemes, thus maintaining more accurate topology information. In Phase 2, we develop a heuristic call-by-call algorithm, based on each edge's minimum normalized slackness to the QoS requested, for selecting a feasible path efficiently in depth first search (DFS)-like manner on the graph and tailoring to each application's QoS requirements. Note that our routing scheme is one of a few QoS-based hierarchical routing schemes that address explicitly the issue of selecting a path with multiple metrics.

Design and implementation of a cooperative multimedia environment with QoS control

The spread of distributed multimedia applications is setting forth a new set of challenges in the management of host and network resources for guaranteeing QUALITY AND SERVICE (QoS). When the multimedia applications compete for resources, as in the case of a cooperative multimedia environment, the management task becomes even more difficult.We have developed a cooperative multimedia environment (CME) that manages multimedia services and the underlying resources in an integrated way. Each user is provided with a single interface to invite other users to a cooperative session, select the media services to be used in the session, and specify his QoS requirements for the media services throughout the session. In this work, we describe the architectural details of the CME and its components with particular emphasis on the QoS mapping and QoS control mechanism. We also present the design and implementation details of an experimental prototype that provides video, audio and white board services.

Video Integration in Multimedia Applications and the Use of Various Delivery Channels

Multimedia applications, until now, were more or less based on standalone computer systems. In conjunction with the use of different delivery channels, these systems are being distributed more frequently. The extended use of the Internet as well as the introduction of digital video delivery offer the opportunity to establish new services. Especially in this changing context, current definitions of the term multimedia are no longer valid, and additional aspects have to be considered when analyzing multimedia systems. Against this background, this paper will present a general description of the different aspects of multimedia systems. Moreover, it will point out the user-centered approach that should be inherent to these systems, as well as technological issues resulting from this approach. — High-definition multimedia or the “CIIQ”-principle is one approach, described in detail in this paper, which follows this comprehensive view on multimedia and the user-centered approach. This principle considers the major aspects completeness, interaction, integration, and quality in the development and use of multimedia systems. Based on this description, the aspects quality, integration, and interactivity of multimedia systems will be discussed in more detail in conjunction with the use and integration of video data. It will be shown that video scaling and the use of compressed data are important factors determining the quality of video streams in distributed multimedia applications. Furthermore, the aspect integration leads to the discussion of the use and combination of various delivery channels. Conventional television, World Wide Web (WWW), and Interactive Television are keywords that are relevant today, and from them a question arises regarding the way combinations of these services and their used delivery channels can be reached. Using dynamically assembled delivery channels offer enhanced interactivity mechanisms; hence new approaches are discussed that lead to extended user interactivity and new applications. At the end of this paper, the discussions are summarized and relevant issues concerning multimedia authoring, standardization, and regulation will be discussed.

A dynamic quality of service framework for video in broadband networks

A dynamic framework for QoS control of video in distributed multimedia applications is presented. The framework allows flexible and efficient video delivery with application-level QoS support. Key components of the framework are client QoS renegotiation, server source rate control, and dynamic bandwidth allocation. The coordinated functionality of these distributed components provides soft QoS to adaptive applications. A proof-of-concept prototype of a video browser with user-level control of soft QoS is implemented within the proposed framework. The implementation uses a distributed software architecture that represents soft QoS requirements by software objects called service contracts. These objects are exchanged among servers, network nodes, and clients to achieve distributed soft QoS control. Experiences with the prototype and its performance are discussed.

Delayed Frame Transmission Schemes for MPEG Videos in a Real-Time

In recent years, real-time systems are likely to be based on distributed architectures and utilize highly parallel algorithms. In such systems, cooperative tasks may be executed on different processors and communicate among each other via a high-speed network. With the growing demand on transmitting digital video in distributed multimedia applications, there is a need to study the on-time delivery of videos over a distributed system. Knowing the fact that unregulated transmission of MPEG video over a computer network may be hazardous to the network performance, in this paper, we exploit the characteristics of MPEG coded frame sequence and devise three transmission schemes for the MPEG video. The crux of the issue is to fully utilize the assigned bandwidth. In our schemes, the delayed frames mechanism can effectively utilize the assigned bandwidth and meet the objective of maximizing the number of video streams that can be supported in a timed token MAC network without sacrificing the video quality. Multiple classes of MPEG video are used in the study. These data are captured from real video programmes and we categorize these video clips according to their traffic burstiness and workload characteristics. The results reveal that by employing the Inter-stream Delayed Transmission Scheme, we could improve the performance by 66 to 166% depending on the availability of global information. When the technique is applied in an intra-stream level, we could improve the performance by 86%. When we combined these two schemes together, the performance improvement of the Total Delayed Transmission Scheme can be pushed to 178% which is a dramatic improvement over the original unregulated transmission scheme.

Routing with multiple QoS requirements for supporting multimedia applications

Distributed multimedia applications usually require multiple QoS performance guarantees. However, in general, searching such a route in the network, to support multimedia applications, is known to be NP?complete. In this paper, we propose a new heuristic QoS routing algorithm, called "QoSRDKS", for supporting multimedia applications in high?speed networks. QoSRDKS is a modification of rule?based Fallback routing and Dijkstra algorithms. It can search a unicast route that would have enough network resources so that multiple QoS requirements (bandwidth, delay, and delay jitter) of the requested flow could be guaranteed. Its worst case computation time complexity is the same as that of the Dijkstra algorithm, i.e., O(?V?2), where ?V? is the number of nodes in the network. Extensive simulations were done with various network sizes, upto 500 nodes networks, where each node uses Weighted Fair Queueing (WFQ) service discipline. Results show that QoSRDKS is very efficient. It could always find the QoS satisfying route, whenever there exists one (success rate is optimal), and its average computation time is near to simple shortest path Dijkstra algorithm.

Switcherland: A scalable interconnection structure for distributed systems

Switcherland is a scalable interconnection structure for distributed systems. It is scalable in that it uses switches that can serve as an I/O interconnection structure of a workstation as well as a network interconnection structure of a cluster of workstations. Switcherland realizes a distributed shared memory, that is, local communication within a workstation as well as remote communication within a cluster of workstations translate to load and store operations. Further, Switcherland offers quality of service (QoS) in that memory is accessed at guaranteed rates and in bounded time. The “natural” programming model offered by the distributed shared memory and the real-time support provided in the form of QoS make Switcherland an ideal platform for distributed multimedia applications.

A programmable transport architecture with QoS guarantees

The emergence of distributed multimedia applications exhibiting significantly more stringent quality of service requirements than conventional data-oriented applications calls for new transport protocols with different characteristics to coexist and be integrated within single applications. The different delivery requirements posed by these diverse multimedia applications often imply the need for highly customized protocol implementations. Hence, application developers are faced with the threat of code obsolescence caused by the development of even newer delivery techniques. We present an object-oriented transport architecture that allows for dynamically binding a variety of protocol stacks on a per-call basis. By binding protocol stacks together, the special needs of the application can be met without the need to rewrite the code. This differs significantly from the traditional transport architecture which assumes preinstalled transport protocol stacks that cannot be customized. To illustrate some of the advantages provided by the architecture, we describe the transport component of the first reference implementation of the 150 MPEG-4 Delivery Multimedia Integration Framework and demonstrate how quickly it was implemented in our framework.

Construction Of Reservation-based Multicast TreesFor Networked Multimedia Services

Distributed multimedia applications make extensive use of real-time multicast streams to implement a new class of services based on the distribution of digital audio and video. Examples of these services are those offered by video-on-demand servers and videoconferencing systems. In such applications, the source delivers a continuous data stream to multiple destinations. This can be logically represented as a tree-shaped communication channel in which the source is the root of the tree and the destinations the leaves .A general problem in this area is the construction of the multicast tree that connects the data source with the destinations. This task is normally accomplished by so-called reservation protocols (e.g., RSVP or ST2+). These protocols not only select the connection paths based on a routing algorithm, but also reserve critical resources (e.g., network bandwidth) over such links. Insufficient resources availability over the selected path causes a connection rejection. This paper discusses an improvement to this scheme. In particular, when a reservation should be rejected because of the unavailability of the requested resource, an alternative could be to try the same reservation on a different path. To this end, the routing protocol should be capable of redrawing the Shortest Path Tree (SPT) without the links or nodes that have provoked the rejection. In the paper, we discuss a strategy for minimising the computational effort by exploiting the knowledge of an initial SPT as calculated for the network without resource reservation constraints. The strategy is based on a centralised version of the Bellman-Ford algorithm, and assumes a linear representation of the above SPT as the scan order for propagating the lowest costs. In such a context, we demonstrate the efficiency of this approach compared with the time performances of the Dijkstra algorithm. The experiments were carried out over sample Transactions on Information and Communications Technologies vol 15, © 1997 WIT Press, www.witpress.com, ISSN 1743-3517

Quality-of-service architecture: monitoring and control of multimedia communications

For distributed multimedia applications the provision of system-wide quality of service (QoS) is essential. The quality-of-service architecture (QoS-A) developed at Lancaster University offers a framework to specify and implement the required performance properties of multimedia applications over integrated-service networks in a heterogeneous environment. The work addresses the problem of lower-level QoS as well as QoS support for multipeer multimedia applications operating in an open communication system. QoS filters have been developed to deal with the problems of heterogeneity in group communication environments. New challenges are also encountered in emerging mobile networks and user mobility; and recent developments in the Internet community highlight the need for appropriate QoS support mechanisms for multimedia applications. The paper describes how the QoS-A research at Lancaster University provides a flexible framework for the monitoring and control of multimedia communications across the broad range of computing systems and networks.