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1.
Domenico Ferrari 《Multimedia Systems》1996,4(6):299-304
Protocols for multimedia communication are needed to integrate into a single network services intended to satisfy the different
requirements of multiple types of traffic. An essential prerequisite for designing these protocols is that the services to
be offered by the network must be selected and specified in detail. We present the service models proposed, or being developed,
by the Internet community, by the ATM community, and by the Tenet Group. We compare their common characteristics, which reveal
the characteristics of the first integrated services networks are likely to offer. The services referred to in this paper
are those at the network and transport layers, which support the services to be offered to the system's end users. 相似文献
2.
We present end-to-end performance of digital coded video (JPEG, MPEG-1, and MPEG-2) over a local asynchronuous transfer mode
(ATM) network. We discuss performance in terms of both delay (jitter) and frame loss as a function of load. The experimental
data reveal that the burstiness of the variable bit-rate-coded video streams degrades the performance significantly when the
hosts and the network are stressed. Our results show that traffic smoothing decreases frame loss significantly while maintaining
acceptable jitter and loss bounds. We also discuss requirements for system components, such as the network interface and switch,
which are necessary to support video services efficiently. 相似文献
3.
A buffer-inventory-based dynamic scheduling algorithm for multimedia-on-demand servers 总被引:2,自引:0,他引:2
We present a producer-consumer model of multimedia-on-demand (MOD) servers. The producer retrieves media data from a disk
and places it into a set of buffers, while the consumer sends out the data in the buffers to the users. We develop for the
producer a buffer-inventory-based dynamic scheduling (BIDS) algorithm that guarantees non-zero inventory and non-overflow
of data in the buffers to meet the continuity requirement and no-loss of data for each media stream. The algorithm can deal
with heterogeneous me dia streams as well as the transient circumstances upon service completions and arrivals of new requests.
To smooth out the impact of bursty data of variable-bit-rate media streams and therefore increase the maximum admissible load
of requests, we also introduce into the scheduling scheme a time-scale-dependent peak consumption rate and a virtual cycle
time. Based on BIDS, an effective admission control mechanism can be easily established by checking two simple conditions
respectively on the overall system load and buffer size. Our algorithm is very easy to implement. Experiments carried out
with an actual disk system and real video stream data verify that it is more robust compared to static scheduling algorithms
previously proposed in the literature, especially when handling variable-bit-rate media streams. 相似文献
4.
Video services are likely to dominate the traffic in future broadband networks. Most of these services will be provided by
large- scale public-access video servers. Research to date has shown that disk arrays are a promising technology for providing
the storage and throughput required to serve many independent video streams to a large customer population. Large disk arrays,
however, are susceptible to disk failures which can greatly affect their reliability. In this paper, we discuss suitable redundancy
mechanisms to increase the reliability of disk arrays and compare the performance of the RAID-3 and RAID-5 redundancy schemes.
We use cost and performability analyses to rigorously compare the two schemes over a variety of conditions. Accurate cost
models are developed and Markov reward models (with time-dependent reward structures) are developed and used to give insight
into the tradeoffs between system cost and revenue earning potential. The paper concludes that for large-scale video servers,
coarse-grained striping in a RAID-5 style of disk array is most cost effective. 相似文献
5.
A network that offers deterministic, i.e., worst case, quality-of-service guarantees to variable-bit-rate (VBR) video must
provide a resource reservation mechanism that allocates bandwidth, buffer space, and other resources for each video stream.
Such a resource reservation scheme must be carefully designed, otherwise network resources are wasted. A key component for
the design of a resource reservation scheme is the traffic characterization method that specifies the traffic arrivals on a video stream. The traffic characterization should accurately describe the
actual arrivals, so that a large number of streams can be supported; but it must also map directly into efficient traffic-policing
mechanisms that monitor arrivals on each stream. In this study, we present a fast and accurate traffic characterization method
for stored VBR video in networks with a deterministic service. We use this approximation to obtain a traffic characterization
that can be efficiently policed by a small number of leaky buckets. We present a case study where we apply our characterization
method to networks that employ a dynamic resource reservation scheme with renegotiation. We use traces from a set of 25–30-min
MPEG sequences to evaluate our method against other characterization schemes from the literature. 相似文献
6.
Nevzat Hurkan Balkir Gultekin Ozsoyoglu 《The VLDB Journal The International Journal on Very Large Data Bases》1998,7(4):294-307
Most multimedia servers reported in the literature are designed to serve multiple and independent video/audio streams. We
think that, in future, multimedia servers will also serve complete presentations. Multimedia presentations provide unique
opportunities to develop algorithms for buffer management and admission control, as execution-time consumption requirements
of presentations are known a priori. In this paper, we examine presentations in three different domains (heavyweight, middleweight,
and lightweight) and provide buffer management and admission control algorithms for the three domains. We propose two improvements
(flattening and dynamic-adjustments) on the schedules created for the heavyweight presentations. Results from a simulation
environment are presented.
Received June 9, 1998 / Accepted October 13, 1998 相似文献
7.
Due to recent advances in network, storage and data compression technologies, video-on-demand (VOD) service has become economically
feasible. It is a challenging task to design a video storage server that can efficiently service a large number of concurrent
requests on demand. One approach to accomplishing this task is to reduce the I/O demand to the VOD server through data- and
resource-sharing techniques. One form of data sharing is the stream-merging approach proposed in [5]. In this paper, we formalize a static version of the stream-merging problem, derive an upper bound on the
I/O demand of static stream merging, and propose efficient heuristic algorithms for both static and dynamic versions of the
stream-merging problem. 相似文献
8.
An optimal bandwidth allocation strategy for the delivery of compressed prerecorded video 总被引:1,自引:0,他引:1
The transportation of prerecorded, compressed video data without loss of picture quality requires the network and video
servers to support large fluctuations in bandwidth requirements. Fully utilizing a client-side buffer for smoothing bandwidth
requirements can limit the fluctuations in bandwidth required from the underlying network and the video-on-demand servers.
This paper shows that, for a fixed-size buffer constraint, the critical bandwidth allocation technique results in plans
for continuous playback of stored video that have (1) the minimum number of bandwidth increases, (2) the smallest peak bandwidth
requirements, and (3) the largest minimum bandwidth requirements. In addition, this paper introduces an optimal bandwidth allocation algorithm which, in addition to the three critical bandwidth allocation properties, minimizes the total number of bandwidth
changes necessary for continuous playback. A comparison between the optimal bandwidth allocation algorithm and other critical
bandwidth-based algorithms using 17 full-length movie videos and 3 seminar videos is also presented. 相似文献
9.
A large-scale, distributed video-on-demand (VOD) system allows geographically dispersed residential and business users to
access video services, such as movies and other multimedia programs or documents on demand from video servers on a high-speed
network. In this paper, we first demonstrate through analysis and simulation the need for a hierarchical architecture for
the VOD distribution network.We then assume a hierarchical architecture, which fits the existing tree topology used in today's
cable TV (CATV) hybrid fiber/coaxial (HFC) distribution networks. We develop a model for the video program placement, configuration,
and performance evaluation of such systems. Our approach takes into account the user behavior, the fact that the user requests
are transmitted over a shared channel before reaching the video server containing the requested program, the fact that the
input/output (I/O) capacity of the video servers is the costlier resource, and finally the communication cost. In addition,
our model employs batching of user requests at the video servers. We study the effect of batching on the performance of the
video servers and on the quality of service (QoS) delivered to the user, and we contribute dynamic batching policies which
improve server utilization, user QoS, and lower the servers' cost. The evaluation is based on an extensive analytical and
simulation study. 相似文献
10.
Efficient admission control algorithms for multimedia servers 总被引:3,自引:0,他引:3
In this paper, we have proposed efficient admission control algorithms for multimedia storage servers that are providers
of variable-bit-rate media streams. The proposed schemes are based on a slicing technique and use aggressive methods for admission
control. We have developed two types of admission control schemes: Future-Max (FM) and Interval Estimation (IE). The FM algorithm uses the maximum bandwidth requirement of the future to estimate the bandwidth requirement. The IE
algorithm defines a class of admission control schemes that use a combination of the maximum and average bandwidths within
each interval to estimate the bandwidth requirement of the interval. The performance evaluations done through simulations
show that the server utilization is improved by using the FM and IE algorithms. Furthermore, the quality of service is also
improved by using the FM and IE algorithms. Several results depicting the trade-off between the implementation complexity,
the desired accuracy, the number of accepted requests, and the quality of service are presented. 相似文献
11.
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. 相似文献
12.
For admission control in real-time multimedia systems, buffer space, disk bandwidth and network bandwidth must be considered.
The CBR-based mechanisms do not use system resources effectively, since media data is usually encoded with VBR compression
techniques. We propose an admission control mechanism based on a VBR data model that has a dynamic period length. In our mechanism,
the period can be adaptively changed to maximize the performance, considering both disk bandwidth and buffer space. To compare
the performance, extensive simulations are conducted on RR, SCAN, and GSS schemes which have the dynamic period length and
the static period length. 相似文献
13.
Control of perceived quality of service in multimedia retrieval services: prediction-based mechanism vs. compensation buffers 总被引:3,自引:0,他引:3
Aurelio La Corte Alfio Lombardo Sergio Palazzo Giovanni Schembra 《Multimedia Systems》1998,6(2):102-112
In multimedia systems end-to-end delay jitter has a great impact on the continuity of information playback. Therefore, it
is necessary to introduce appropriate mechanisms to compensate for delay variations, so that the intramedia and intermedia
temporal relationships can be preserved. In this paper, two methods for compensation of the network delay jitter in a distributed
multimedia retrieval service are compared: the first is based on prediction of the network delay jitter suffered by each information
unit and retrieval time modification at the source site; the second is based on a compensation buffer at the destination site.
Comparison is made by assuming a master/slave relationship between the monomedia streams composing the multimedia data flow. 相似文献
14.
Edward W. Knightly 《Multimedia Systems》1999,7(6):477-485
In order for networks to support the delay and loss requirements of interactive multimedia applications, resource management
algorithms are needed that efficiently allocate network resources. In this paper, we introduce a new resource allocation scheme
based on rate variance envelopes. Such envelopes capture a flow's burstiness properties and autocorrelation structure by characterizing
the variance of its rate distribution over intervals of different length. From this traffic characterization, we develop a
simple and efficient resource allocation algorithm for static priority schedulers by employing a Gaussian approximation over
intervals and considering a maximal busy period. Our approach supports heterogeneous quality-of-service requirements via our
consideration of prioritized service disciplines, and supports heterogeneous and bursty traffic flows via our general framework
of traffic envelopes. To evaluate the scheme, we perform trace-driven simulation experiments with long traces of compressed
video and show that our approach is accurate enough to capture most of the available statistical multiplexing gain, achieving
average network utilizations of up to 90% for these traces and substantially outperforming alternate schemes. 相似文献
15.
Recently, a number of studies have been made based on the concept of Route Interference to provide deterministic end-to-end quality of service (QoS) guarantees. Nonetheless, these studies tend to confine to a simple scheduling scheme and study the traffic in a single-class environment or the highest priority traffic in a multi-class environment. This is rather restrictive. In this paper, we propose a new general service scheme to service flows. This scheme is represented by a Latency-Rate Max–Min service curve (LRMMSC). Subsequently, for a network of LRMMSC, we prove the existence of tight bounds on end-to-end queuing delay and buffer size needed for loss-free packet delivery, provided that all flows obey a given source rate condition in the form of their route interference. Our approach has two salient features: (1) the general nature of the concept of service curve enables the service scheme to be implemented by many well-known scheduling disciplines, (2) the general network model adopted with no constraints on the manner of packet queuing makes the results applicable to many complex networks. In addition, we have also derived a concise expression of end-to-end delay bound that depends only on the service offered to the buffers containing the considered flow. This is very useful in practice as the expression is simple and requires minimum amount of information input. Simulation experiments are conducted to verify the LRMMSC model. The analytical and simulation results exhibit close resemblance. In addition, the advantage of LRMMSC scheme in providing maximum end-to-end delay is also demonstrated. 相似文献
16.
In this paper, we propose and study a dynamic approach to schedule real-time requests in a video-on-demand (VOD) server.
Providing quality of service in such servers requires uninterrupted and on-time retrieval of motion video data. VOD services
and multimedia applications further require access to the storage devices to be shared among multiple concurrent streams.
Most of the previous VOD scheduling approaches use limited run-time,0 information and thus cannot exploit the potential capacity
of the system fully. Our approach improves throughput by making use of run-time information to relax admission control. It
maintains excellent quality of service under varying playout rates by observing deadlines and by reallocating resources to
guarantee continuous service. It also reduces start-up latency by beginning service as soon as it is detected that deadlines
of all real-time requests will be met. We establish safe conditions for greedy admission, dynamic control of disk read sizes,
fast initial service, and sporadic services. We conduct thorough simulations over a wide range of buffer capacities, load
settings, and over varying playout rates to demonstrate the significant improvements in quality of service, throughput and
start-up latency of our approach relative to a static approach. 相似文献
17.
In this paper, we investigate a playout scheduling framework for supporting the continuous and synchronized presentations
of multimedia streams in a distributed multimedia presentation system. We assume a situation in which the server and network
transmissions provide sufficient support for the delivery of media objects. In this context, major issues regarding the enforcement
of the smooth presentation of multimedia streams at client sites must be addressed to deal with rate variance of stream presentations
and delay variance of networks. We develop various playout-scheduling algorithms that are adaptable to quality-of-service
parameters. The proposed algorithms permit the local adjustment of unsynchronized presentations by gradually accelerating
or retarding presentation components, rather than abruptly skipping or pausing the presentation materials. A comprehensive
experimental analysis of the proposed algorithms demonstrates that our algorithms can effectively avoid playout gaps (or hiccups)
in the presentations. This scheduling framework can be readily used to support customized multimedia presentations. 相似文献
18.
Summary. Different replication algorithms provide different solutions to the same basic problem. However, there is no precise specification
of the problem itself, only of particular classes of solutions, such as active replication and primary-backup. Having a precise
specification of the problem would help us better understand the space of possible solutions and possibly come out with new
ones. We present a formal definition of the problem solved by replication in the form of a correctness criterion called x-ability (exactly-once ability). An x-able service has obligations to its environment and its clients. It must update its environment
under exactly-once semantics. Furthermore, it must provide idempotent, non-blocking request processing and deliver consistent
results to its clients. We illustrate the value of x-ability through a novel replication protocol that handles non-determinism
and external side-effects. The replication protocol is asynchronous in the sense that it may vary, at run-time and according
to the asynchrony of the system, between some form of primary-backup and some form of active replication.
Received: December 2000 / Accepted: September 2001 相似文献
19.
20.
Transporting QoS adaptive flows 总被引:4,自引:0,他引:4
Distributed audio and video applications need to adapt to fluctuations in delivered quality of service (QoS). By trading
off temporal and spatial quality to available bandwidth, or manipulating the playout time of continuous media in response
to variation in delay, audio and video flows can be made to adapt to fluctuating QoS with minimal perceptual distortion. In
this paper, we extend our previous work on a QoS Architecture (QoS-A) by populating the QoS management planes of our architecture
with a framework for the control and management of multilayer coded flows operating in heterogeneous multimedia networking
environments. Two key techniques are proposed: i) an end-to-end rate-shaping scheme which adapts the rate of MPEG-coded flows
to the available network resources while minimizing the distortion observed at the receiver; and ii) an adaptive network service,
which offers “hard” guarantees to the base layer of multilayer coded flows and “fairness” guarantees to the enhancement layers
based on a bandwidth allocation technique called Weighted Fair Sharing. 相似文献