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1.
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
2.
Managing database server performance to meet QoS requirements in electronic commerce systems 总被引:1,自引:0,他引:1
Patrick Martin Wendy Powley Hoi-Ying Li Keri Romanufa 《International Journal on Digital Libraries》2002,3(4):316-324
The performance of electronic commerce systems has a major impact on their acceptability to users. Different users also demand
different levels of performance from the system, that is, they will have different Quality of Service (QoS) requirements. Electronic commerce systems are the integration of several different types of servers and each server must
contribute to meeting the QoS demands of the users. In this paper we focus on the role, and the performance, of a database server within an electronic commerce system.
We examine the characteristics of the workload placed on a database server by an electronic commerce system and suggest a
range of QoS requirements for the database server based on this analysis of the workload. We argue that a database server
must be able to dynamically reallocate its resources in order to meet the QoS requirements of different transactions as the
workload changes. We describe Quartermaster, which is a system to support dynamic goal-oriented resource management in database
management systems, and discuss how it can be used to help meet the QoS requirements of the electronic commerce database server.
We provide an example of the use of Quartermaster that illustrates how the dynamic reallocation of memory resources can be
used to meet the QoS requirements of a set of transactions similar to transactions found in an electronic commerce workload.
We briefly describe the memory reallocation algorithms used by Quartermaster and present experiments to show the impact of
the reallocations on the performance of the transactions.
Published online: 22 August 2001 相似文献
3.
As a result of the rapid growth of Cloud Computing, several Cloud middleware solutions for the creation and automated management of virtual appliances have been released. Generally, these solutions offer some predefined scheduling policies to manage the provider infrastructure, but additional tuning of the policies is often needed to fully align their behavior with the provider interests. However, current middleware solutions do not offer ways to do this without stopping and recompiling the middleware. This paper proposes a solution that separates scheduling policies from the managers that interpret them, to allow the behavior of the management system to be changed without re-coding the managers. In this way, the middleware can adapt to changing requirements by disabling policies or replacing old policies with new ones without shutting down the system. We propose a new policy language for the definition of management policies and we enable the EMOTIVE Cloud middleware to use these policies by integrating in the middleware the needed policy management framework for parsing and generating code on demand. We demonstrate with real experiments that our policy management framework mimics the expressiveness of scheduling policies in real Cloud middleware and provides more expressiveness if needed. The overhead of the policy management framework is low, but its performance degrades, especially in large datacenters, due to the low scalability of the EMOTIVE monitoring solution. 相似文献
4.
Mobile computing systems should be self-managed to simplify operation and maintenance plus meet user’s expectation with respect
to Quality of Service (QoS). When architecting self-managed mobile computing systems, one must take a holistic view on both
QoS management and the entities in the mobile environment. This paper presents a novel model that includes both resources
and context elements. To illustrate the usefulness of the model, it is applied to a video streaming application by: (1) modelling
context elements and resources in the environment, (2) specifying context dependencies and QoS characteristics of the application,
and (3) designing weakly integrated resource and context managers. We describe a middleware that uses the developed managers
when evaluating context dependencies and predict offered QoS of alternative implementations of the application. In order to
select the one that can operate in the current environment and that best satisfies given user preferences. 相似文献
5.
A. Schulte 《Cognition, Technology & Work》2002,4(3):146-159
This paper describes an approach to cognitive and cooperative operator assistance in the field of tactical flight mission
management. A framework for a generic functional concept is derived from general considerations of human performance and cognitive
engineering. A system built according to these human-centred design principles will be able to keep up with the change of
situation parameters, in order to provide situational adapted operator assistance. Such a cognitive assistant system represents an approach to ensure the highest degree possible of situation awareness of the flight deck crew as well as a
satisfactory workload level. This generic approach to mission management and crew assistance for military aircraft has been
realised in different application domains such as military transport and air-to-ground attack. The Crew Assistant Military Aircraft is a functional prototype for the air transport application. Even applications in the domain of uninhabited aerial vehicles
(UAV) are in reach. This paper mainly covers one state-of-the-art research and development activity in the domain of combat
aircraft: the TMM – Tactical Mission Management System is an experimental solution for the air-to-ground attack role. The TMM has been implemented as a functional prototype in
the mission avionics experimental cockpit (MAXC), a development flight simulator at ESG and evaluated with German Air Force
pilots as subjects in simulator trials. Therefore, the TMM has been compared with a reference cockpit avionics configuration
in terms of task performance, workload, situation awareness and operator acceptance. After giving an overview of the system
concepts this paper reports on the experimental design and results of the simulator trial campaign. 相似文献
6.
Multimedia systems must be able to support a certain quality of service (QoS) to satisfy the stringent real-time performance
requirements of their applications. HeiRAT, the Heidelberg Resource Administration Technique, is a comprehensive QoS management
system that was designed and implemented in connection with a distributed multimedia platform for networked PCs and workstations.
HeiRAT includes techniques for QoS negotiation, QoS calculation, resource reservation, and resource scheduling for local and
network resources. 相似文献
7.
Repantis Thomas Gu Xiaohui Kalogeraki Vana 《Parallel and Distributed Systems, IEEE Transactions on》2009,20(7):968-982
Many emerging online data analysis applications require applying continuous query operations such as correlation, aggregation, and filtering to data streams in real time. Distributed stream processing systems allow in-network stream processing to achieve better scalability and quality-of-service (QoS) provision. In this paper, we present Synergy, a novel distributed stream processing middleware that provides automatic sharing-aware component composition capability. Synergy enables efficient reuse of both result streams and processing components, while composing distributed stream processing applications with QoS demands. It provides a set of fully distributed algorithms to discover and evaluate the reusability of available result streams and processing components when instantiating new stream applications. Specifically, Synergy performs QoS impact projection to examine whether the shared processing can cause QoS violations on currently running applications. The QoS impact projection algorithm can handle different types of streams including both regular traffic and bursty traffic. If no existing processing components can be reused, Synergy dynamically deploys new components at strategic locations to satisfy new application requests. We have implemented a prototype of the Synergy middleware and evaluated its performance on both PlanetLab and simulation testbeds. The experimental results show that Synergy can achieve much better resource utilization and QoS provisioning than previously proposed schemes, by judiciously sharing streams and components during application composition. 相似文献
8.
Global transaction support for workflow management systems: from formal specification to practical implementation 总被引:6,自引:0,他引:6
Paul Grefen Jochem Vonk Peter Apers 《The VLDB Journal The International Journal on Very Large Data Bases》2001,10(4):316-333
In this paper, we present an approach to global transaction management in workflow environments. The transaction mechanism
is based on the well-known notion of compensation, but extended to deal with both arbitrary process structures to allow cycles
in processes and safepoints to allow partial compensation of processes. We present a formal specification of the transaction
model and transaction management algorithms in set and graph theory, providing clear, unambiguous transaction semantics. The
specification is straightforwardly mapped to a modular architecture, the implementation of which is first applied in a testing
environment, then in the prototype of a commercial workflow management system. The modular nature of the resulting system
allows easy distribution using middleware technology. The path from abstract semantics specification to concrete, real-world
implementation of a workflow transaction mechanism is thus covered in a complete and coherent fashion. As such, this paper
provides a complete framework for the application of well-founded transactional workflows.
Received: 16 November 1999 / Accepted 29 August 2001 Published online: 6 November 2001 相似文献
9.
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
10.
We present a high-performance solution to the I/O retrieval problem in a distributed multimedia system. Parallelism of data
retrieval is achieved by striping the data across multiple disks. We identify the components that contribute to media data-retrieval
delay. The variable delays among these have a great bearing on the server throughput under varying load conditions. We present
a buffering scheme to minimize these variations. We have implemented our model on the Intel Paragon parallel computer. The
results of component-wise instrumentation of the server operation are presented and analyzed. Experimental results that demonstrate
the efficacy of the buffering scheme are presented. Based on our experiments, a dynamic admission-control policy that takes
server workloads into account is proposed. 相似文献
11.
12.
We present efficient schemes for scheduling the delivery of variable-bit-rate MPEG-compressed video with stringent quality-of-service
(QoS) requirements. Video scheduling is being used to improve bandwidth allocation at a video server that uses statistical
multiplexing to aggregate video streams prior to transporting them over a network. A video stream is modeled using a traffic
envelope that provides a deterministic time-varying bound on the bit rate. Because of the periodicity in which frame types
in an MPEG stream are typically generated, a simple traffic envelope can be constructed using only five parameters. Using
the traffic-envelope model, we show that video sources can be statistically multiplexed with an effective bandwidth that is often less than the source peak rate. Bandwidth gain is achieved without sacrificing the stringency of the requested
QoS. The effective bandwidth depends on the arrangement of the multiplexed streams, which is a measure of the lag between the GOP periods of various streams. For homogeneous streams,
we give an optimal scheduling scheme for video sources at a video-on-demand server that results in the minimum effective bandwidth.
For heterogeneous sources, a sub-optimal scheduling scheme is given, which achieves acceptable bandwidth gain. Numerical examples
based on traces of MPEG-coded movies are used to demonstrate the effectiveness of our schemes. 相似文献
13.
Peter A. Boncz Martin L. Kersten 《The VLDB Journal The International Journal on Very Large Data Bases》1999,8(2):101-119
In query-intensive database application areas, like decision support and data mining, systems that use vertical fragmentation
have a significant performance advantage. In order to support relational or object oriented applications on top of such a
fragmented data model, a flexible yet powerful intermediate language is needed. This problem has been successfully tackled
in Monet, a modern extensible database kernel developed by our group. We focus on the design choices made in the Monet interpreter
language (MIL), its algebraic query language, and outline how its concept of tactical optimization enhances and simplifies
the optimization of complex queries. Finally, we summarize the experience gained in Monet by creating a highly efficient implementation
of MIL.
Received November 10, 1998 / Accepted March 22, 1999 相似文献
14.
Sharma P.K. Loyall J. Schantz R.E. Ye J. Manghwani P. Gillen M. Heineman G.T. 《Internet Computing, IEEE》2006,10(3):16-23
Maintaining end-to-end quality of service (QoS) is a challenge in distributed real time embedded systems due to dynamically changing network environments and resource requirements. The authors' middleware QoS management approach encapsulates QoS behaviors as software components. Using the Corba component model, they build these specialized QoS components and combine them to produce a comprehensive management system that maintains QoS. The authors illustrate the approach by building a real-world medium-scale system with these components. Using this example, they demonstrate the reusability of each component in different contexts. 相似文献
15.
服务质量QoS管理是满足分布式环境中端到端QoS需求的关键,而中间件是一种分布式系统中的主要交互平台.首先对中间件和QoS的相关概念进行介绍,在分析传统QoS管理模型的基础上,提出一种基于消息中间件(MOM)的QoS管理模型,重点分析多维QoS在该模型中的应用,最后结合一个实例说明多维QoS在实际系统中的应用. 相似文献
16.
Many video applications tolerate continuous media (CM) scaling. Scaling is acceptable due to human tolerance to degradation
in picture quality, frame loss, and end-to-end delay. CM scaling enables the network to utilize its resources efficiently
for supporting additional customers and to increase its revenue. However, due to quality degradation, users will not be willing
to tolerate scaling unless it is coupled with monetary or availability incentives. We propose a pricing policy and a corresponding
admission control scheme for scalable video applications. The pricing policy is two-tiered, based on a connection set-up component
and a scalable component. Connections that are more scalable are charged less, but are more liable to be degraded. The proposed
policy trades off performance degradation with monetary incentives to improve user benefit and network revenue and to decrease
the blocking probability of connection requests. We demonstrate by means of simulation that this policy encourages users to
specify the scalability of an application to the network. 相似文献
17.
18.
Claudia Wenzel Heiko Maus 《International Journal on Document Analysis and Recognition》2001,3(4):248-260
Knowledge-based systems for document analysis and understanding (DAU) are quite useful whenever analysis has to deal with
the changing of free-form document types which require different analysis components. In this case, declarative modeling is
a good way to achieve flexibility. An important application domain for such systems is the business letter domain. Here, high
accuracy and the correct assignment to the right people and the right processes is a crucial success factor. Our solution
to this proposes a comprehensive knowledge-centered approach: we model not only comparatively static knowledge concerning
document properties and analysis results within the same declarative formalism, but we also include the analysis task and
the current context of the system environment within the same formalism. This allows an easy definition of new analysis tasks
and also an efficient and accurate analysis by using expectations about incoming documents as context information. The approach
described has been implemented within the VOPR (VOPR is an acronym for the Virtual Office PRototype.) system. This DAU system
gains the required context information from a commercial workflow management system (WfMS) by constant exchanges of expectations
and analysis tasks. Further interaction between these two systems covers the delivery of results from DAU to the WfMS and
the delivery of corrected results vice versa.
Received June 19, 1999 / Revised November 8, 2000 相似文献
19.
Satellite network users want to unify different satellites to enhance the quality-of-service (QoS) stability of the satellite networks and select feasible paths through different networks to feed different applications. Unfortunately, the state of affairs is that different applications need to use several different application programming interfaces and to design different protocols on how and when to use a specific network. This is troublesome and error-prone as the application programming interfaces vary a lot. In this paper, we design a Virtual Strategy in satellite network based on which a QoS routing service scheme is then proposed. We analyze why applications should use and benefit from Virtual Strategy. This Virtual Strategy is a middleware solution that enables seamless usage of services from different satellite network parts. And then, the supporting QoS routing solution enables the committed QoS services over Virtual Strategy. Finally, we provide a comparison between the previous satellite networks and our work. The simulation results show that our Virtual Strategy QoS routing scheme demonstrates dominated performances under complex architecture. 相似文献
20.
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