Variable-bit-rate compressed video can exhibit significant, multiple-time-scale bit rate variability. In this paper we consider the transmission of stored video from a server to a client across a network, and explore how the client buffer space can be used most effectively toward reducing the variability of the transmitted bit rate. Two basic results are presented. First, we show how to achieve the greatest possible reduction in rate variability when sending stored video to a client with given buffer size. We formally establish the optimality of our approach and illustrate its performance over a set of long MPEG-1 encoded video traces. Second, we evaluate the impact of optimal smoothing on the network resources needed for video transport, under two network service models: Deterministic Guaranteed service [1, 31] and Renegotiated CBR (RCBR) service [9]. Under both models the impact of optimal smoothing is dramatic. 1 Introduction A broad range of applications is enabled by the capac...

Variable bit-rate (VBR) compressed video traffic is expected to be a significant component of the traffic mix in integrated services networks. This traffic is hard to manage because it has strict delay and loss requirements while simultaneously exhibiting burstiness at multiple time scales. We show that burstiness over long time scales, in conjunction with resource reservation using one-shot traffic descriptors, can substantially degrade the loss rate, end-to-end delay, and statistical multiplexing gain of a connection. We use large-deviation theory to model the performance of multiple time-scale traffic and to motivate the design of renegotiated constant bit rate (RCBR) service. Sources using

We suggest that satisfactory statistical performance guarantees for streaming flows can be fulfilled when their packets receive expedited forwarding in non-preemptive priority queues. This relies on the conjecture that jitter remains negligible in the network such that performance measures can be bounded by assuming flows constitute Poisson arrival processes of MTU sized packets. We provide analytical and simulation evidence in support of this conjecture and show how it leads to simple engineering rules for both constant and variable rate streaming traffic. I.

We introduce a new scheduling algorithm for multimedia traffic, using capacity reservation. We compare it to other algorithms in the literature. It has been implemented and its worst-case performance analysed. It appears to give a noticeably improved quality of service to delay-sensitive traffic. 1 Introduction Networked multimedia applications are becoming increasingly important to the business community, and an increasing proportion of the traffic of data networks is used by such applications. Multimedia traffic has different quality of service needs than those provided by most routers, which were designed with regular data traffic in mind. Multimedia traffic is much more sensitive to delay than regular data traffic [20]. Current routing technology gives "best-effort" service, aimed at maximizing throughput, with minor consideration to delay and loss. As a result, some delay-sensitive packets are not delivered in time. We therefore believe that it is worth using a router schedulin...

The Differentiated Service (Diff-Serv) architecture [1] advocates a model based on different "granularity" at network edges and within the network. In particular, core routers are only required to act on a few aggregates, that are meant to offer a pre-defined set of service levels. The use of aggregation raises a number of questions for end-to-end services, in particular when crossing domain boundaries where policing actions may be applied. This paper focuses on the impact of such policing actions in the context of individual and bulk services built on top of the Expedited Forwarding (EF) [7] per-hop-behavior (PHB). The findings of this investigation confirm and quantify the expected need for reshaping at network boundaries. They also make recommendations for when reshaping is not available.

In this paper, a new method is proposed to optimize stored VBR (variable-bit-rate) video transmission on CBR (constant-bit-rate) channel. The proposed method can minimize both the buffer requirement and workahead for a given peak transmission rate. Besides, the network utilization is maximized with the minimum service connection time. These problem parameters are not optimized at the same time in the conventional approaches. In this paper, we at first present the Lazy scheme to determine the minimum buffer and workahead required for a given peak transmission rate. Then, the Aggressive scheme is applied to maximize the system resource utilization (e.g., network bandwidth). The proposed schemes can be easily extended to transmit the VBR video with the minimum rate variability, or to resolve the buffer-constrained transmission problem with the minimum peak transmission rate for a given buffer size. Experiments to many well-known benchmark video traces show that the proposed method can obt...

In a client-server system, the minimum bandwidth required to transmit a pre-recorded VBR media can be computed in O(n). As the frame number n is usually very large, this resource management procedure is not suitable for online computation. Although an O(nlogn) algorithm has been proposed to characterize the bandwidth-buffer tradeoff for the optimal resource management (a native algorithm takes O(n 3 )), this algorithm is not suitable for a general network system with additional relay-server. In this paper, we extend the problem model to consider the relay-server between client and server. This proposed model is good for scalable multimedia and fault-tolerance. Besides, the additional buffer in relay-server can be utilized to further smooth traffic and support more requests. In this paper, an O(nlogn) algorithm is proposed to decide the optimal bandwidth-buffer tradeoff for the relay-server. Based on the pre-computed tradeoff function, we can simply design a good QoS control procedure...

There is a pressing need for Asynchronous Transfer Mode (ATM) traffic measurements to validate/verify a large number of simulation and analytical studies of ATM networks. In this paper, results from a measurement study of traffic on a wide area ATM network, the very High Speed Backbone Network Service (vBNS) network are reported. We illustrate how the traffic characteristics change as the traffic traverses the network and the statistical behavior of wide area ATM traffic. Also, we comment on the validity of a few theoretical assumptions made by other research, offering empirical evidence to support these comments. 1 Introduction Broadband networks of the future will carry audio, video, and data traffic from many diverse applications. The problems of resource management and of guaranteed Quality of Service (QoS) provision to applications in a wide area Asynchronous Transfer Mode (ATM) network are of considerable interest. One issue in configuring the network and developing network con...

Please address all correspondence to Dr. V.C.M. Leung at the above address. Two frame-based ATM scheduling strategies, Delayed Frame Queueing (DFQ) and Virtual Frame Queueing (VFQ), are described for real-time network applications. Both strategies guarantee explicit upper bounds on delay and jitter on a per virtual connection (VC) basis without relying on per-VC queueing. They also resolve the disadvantages often associated with other frame-based schedulers. The DFQ scheduler employs Resource Management cells to enable work-conserving forwarding at intermediate nodes while retaining the option for non-work-conserving forwarding at terminal nodes. This allows delay bounds to be uncoupled from jitter bounds. The VFQ scheduler requires no such overhead cell transmissions, but is more limited in its ability to uncouple these two types of bounds. ATM network simulation results indicate that both proposed disciplines offer favorable multiplexing performance in comparison to a well documented high performance service discipline. Finally, we contrast our proposal against the significant difficulties that alternative scheduling strategies based on bandwidth guarantees will face with regard to network management and network synthesis issues.

Circuit Emulation Service #CES# o#ers backward compatibilitybetween Asynchronous Transfer Mode #ATM# technology and the existing circuit-switched telephony services. However, meeting its quality of service requirements is not trivial. The cell transfer delay #CTD# of a connection should be controlled to be no larger than the delay in legacy circuit-switched networks, which usually imposes a constraint on the play-out bu#er size at the receiver end. Therefore the end-to-end cell delayvariation #CDV# has to be minimized to avoid either over#ow or under#owof the small play-out bu#er. To optimize the CDV performance for ATM CES service, we propose a new multiplexor scheduling scheme called Variation Fluctuation Smoothing #VFS#. VFS estimates the clock of each connection by on-line tra#c measurement. It then calculates the lateness of the head-of-line cell for each connection and assigns the highest priority to the latest cell. By attempting to match cell departures to a virtual clock, VF...