676 research outputs found
On the time scales in video traffic characterization for queueing behavior
To guarantee quality of service (QoS) in future integrated service networks, traffic sources must be characterized to capture the traffic characteristics relevant to network performance. Recent studies reveal that multimedia traffic shows burstiness over multiple time scales and long range dependence (LRD). While researchers agree on the importance of traffic correlation there is no agreement on how much correlation should be incorporated into a traffic model for performance estimation and dimensioning of networks. In this article, we present an approach for defining a relevant time scale for the characterization of VER video traffic in the sense of queueing delay. We first consider the Reich formula and characterize traffic by the Piecewise Linear Arrival Envelope Function (PLAEF). We then define the cutoff interval above which the correlation does not affect the queue buildup. The cutoff interval is the upper bound of the time scale which is required for the estimation of queue size and thus the characterization of VER video traffic. We also give a procedure to approximate the empirical PLAEF with a concave function; this significantly simplifies the calculation in the estimation of the cutoff interval and delay bound with little estimation loss. We quantify the relationship between the time scale in the correlation of video traffic and the queue buildup using a set of experiments with traces of MPEG/JPEG-compressed video. We show that the critical interval i.e. the range for the correlation relevant to the queueing delay, depends on the traffic load: as the traffic load increases, the range of the time scale required for estimation for queueing delay also increases. These results offer further insights into the implication of LRD in VER video traffic. (C) 1999 Elsevier Science B.V. Ail rights reserved
Transport of video over partial order connections
A Partial Order and partial reliable Connection (POC) is an end-to-end transport connection authorized to deliver objects in an order that can differ from the transmitted one. Such a connection is also authorized to lose some objects. The POC concept is motivated by the fact that heterogeneous best-effort networks such as Internet are plagued by unordered delivery of packets and losses, which tax the performances of current applications and protocols. It has been shown, in several research works, that out of order delivery is able to alleviate (with respect to CO service) the use of end systems’ communication resources. In this paper, the efficiency of out-of-sequence delivery on MPEG video streams processing is studied. Firstly, the transport constraints (in terms of order and reliability) that can be relaxed by MPEG video decoders, for improving video transport, are detailed. Then, we analyze the performance gain induced by this approach in terms of blocking times and recovered errors. We demonstrate that POC connections fill not only the conceptual gap between TCP and UDP but also provide real performance improvements for the transport of multimedia streams such MPEG video
Specification of multiparty audio and video interaction based on the Reference Model of Open Distributed Processing
The Reference Model of Open Distributed Processing (RM-ODP) is an emerging ISO/ITU-T standard. It provides a framework of abstractions based on viewpoints, and it defines five viewpoint languages to model open distributed systems. This paper uses the viewpoint languages to specify multiparty audio/video exchange in distributed systems. To the designers of distributed systems, it shows how the concepts and rules of RM-ODP can be applied.\ud
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The ODP ¿binding object¿ is an important concept to model continuous data flows in distributed systems. We take this concept as a basis for multiparty audio and video flow exchanges, and we provide five ODP viewpoint specifications, each emphasising a particular concern. To ensure overall correctness, special attention is paid to the mapping between the ODP viewpoint specifications
Decision Support in Cooperative QoS Management
Cooperative QoS management is a new quality of service management scheme which is based on QoS agents distributed within a system and cooperating with each other to provide the QoS negotiated with users, thereby ameliorating the overail system's resource usage and decreasing the communication costs. During their operations, agents have to take decisions in order to react on QoS violations, initiate QoS renegotiation processes or react on renegotiation requests from other QoS agents. In this paper, we present two tools which support cooperating QoS agents in their decision processes: a model called Quality of Operation, based on a mathematical formula, and an approach based on a new variant of Stochastic Petri Nets, so-called Controlled Stochastic Petri Nets
Integration Protocols for Voice and Data Traffic
Increasing demands for multimedia services offer integration of multimedia
traffic as a hot issue in the future research areas. As a result, in the literature, many
multiplexing schemes have been proposed. However, most of them have been
implemented with a high complexity, others may be non-effective to satisfy the
multiplexing performance criteria, while the rest are still not subjected to a wide
range of analysis. Therefore, there is a critical need for comparing some of the
recommended multiplexing schemes as well as developing a simple and effective
integration protocol while still achieving reasonable bandwidth utilization.
This thesis is intended to examine integration protocols for multimedia traffic,
with primary focusing on voice-data integration. Firstly, a survey of the existing
multiplexing schemes and related issues are presented. Next, an Adaptive Round
Robin (ARR) protocol is proposed, as an alternative for voice-data integration, and
extensively simulated. Finally, further comparisons, based on computer simulations,
are carried out for various multiplexing schemes including Strictly Priority Servicing
(SPS), Fixed Round Robin (FRR), Dynamic Bandwidth Allocation/(T1, T2) and
Queue Length Threshold (QLT).As a contribution of the thesis, the proposed protocol tries to avoid the
drawbacks of the previous multiplexing schemes besides satisfying the multiplexing
performance criteria. The protocol differs from the others in that, it gives a limited
priority for voice over data, it organizes the incoming packets to the single First-in
First-out (FIFO) output buffer rather than the only outgoing scheduling, i.e., all data
sources are polled in order according to the adaptation policy; however, before a data
source can send a packet, all active voice sources are polled in order. Thus it
provides an improvement in voice delay performance without significant effect on
data delay performance over previous protocols. In addition, simulation comparisons
between various multiplexing schemes have been discussed. In these simulations
voice packets are assumed to be generated from on-off sources (talkspurt-silence
calls), which is closer to reality and which is not considered in most of the
performance analyses of previous schemes
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