Advance reservations for predictive service in the Internet

We extend a measurement-based admission control algorithm suggested for predictive service to provide advance reservations for guaranteed and predictive service, while retaining the attractive features of predictive service. The admission decision for advance reservations is based on information about flows that overlap in time. For flows that have not yet started, the requested values are used, and for those that have already started measurements are used. This allows us to estimate the network load accurately for the near future. To provide advance reservations we ask users to include durations in their requests. We present simulation results to show that predictive service with advance reservations provides utilization levels significantly higher than those for guaranteed service, and comparable to those for predicted service without advance reservations. Those utilization levels are reached without any preemption of other admitted flows. Finally, we discuss how to setup advance reservations over multiple hops in the Internet using resource reservation setup protocols.     

A bandwidth adaptation mechanism for Cloud Radio Access Networks

The Cloud Radio Access Network (C-RAN) is regarded as the possible implementation approach of the next-generation mobile networks. C-RAN splits a traditional base station into remote radio heads (RRHs) and the base band unit (BBU). Many BBUs are co-located into a centralized BBU pool. This enables the baseband resources to be managed in a centralized BBU pool and thus improves the efficiency. In this paper, a new bandwidth adaptation (BA) mechanism is designed for the C-RAN with the dual connectivity capability. The dual connectivity allows the bearer to be split so as to access more resources from RRHs simultaneously. The new BA mechanism is developed so as to dynamically allocate the resources to establish a new or a handoff bearer. The new BA mechanism is designed with a new downgrading index, which aims to fairly release the proportional resource from more RRHs and then aggregates the released resource to a new or a handoff bearer. Simulation and analysis results illustrate that the proposed BA mechanism reduces both the handoff bearer dropping and the bearer blocking probabilities.     

A service acquisition mechanism for server-based heterogeneousdistributed systems

This paper presents a mechanism that facilitates and enhances the use of independently administered remote network servers in the presence of server interface heterogeneity. The mechanism is designed under the client-service model, which extends the client-server model with an abstraction of service to decouple abstract server capabilities from concrete server interface specifics such as server interface binding protocols and the interface operation invocation protocols. The mechanism selects servers, accommodates server interface heterogeneity, and handles server access failures as per the abstract server capabilities desired by the client. It could return the identity of the server used for each service access invocation to facilitate billing, refining service specifications, and reporting server-specific errors. This paper also illustrates a C library interface to this mechanism, and describes a language veneer over the C programming language demonstrating how a typed procedural language could be extended by a few language constructs to support the mechanism under the client-service model. In this language, server capabilities are referenced by abstract data type (ADT) objects, and are accessed by invoking the objects' interface operations using a call-by-value-result paradigm     

云服务相关问题研究

"云计算"与网络的发展脱不开关系。有线网络的大提速以及无线网络3G乃至4G的普及,共同编织了能让"云"茁壮成长的环境。"网络即电脑"这一概念,现在正从近乎预言的概念慢慢变成现实。在个人应用领域,"云"正以怎样的形式影响日常生活呢?通过对云服务的简要概述,探讨云服务中存在的若干问题。     

Agent-based Cloud service composition

Service composition in multi-Cloud environments must coordinate self-interested participants, automate service selection, (re)configure distributed services, and deal with incomplete information about Cloud providers and their services. This work proposes an agent-based approach to compose services in multi-Cloud environments for different types of Cloud services: one-time virtualized services, e.g., processing a rendering job, persistent virtualized services, e.g., infrastructure-as-a-service scenarios, vertical services, e.g., integrating homogenous services, and horizontal services, e.g., integrating heterogeneous services. Agents are endowed with a semi-recursive contract net protocol and service capability tables (information catalogs about Cloud participants) to compose services based on consumer requirements. Empirical results obtained from an agent-based testbed show that agents in this work can: successfully compose services to satisfy service requirements, autonomously select services based on dynamic fees, effectively cope with constantly changing consumers’ service needs that trigger updates, and compose services in multiple Clouds even with incomplete information about Cloud participants.     

Cloud computing service composition: A systematic literature review

The increasing tendency of network service users to use cloud computing encourages web service vendors to supply services that have different functional and nonfunctional (quality of service) features and provide them in a service pool. Based on supply and demand rules and because of the exuberant growth of the services that are offered, cloud service brokers face tough competition against each other in providing quality of service enhancements. Such competition leads to a difficult and complicated process to provide simple service selection and composition in supplying composite services in the cloud, which should be considered an NP-hard problem. How to select appropriate services from the service pool, overcome composition restrictions, determine the importance of different quality of service parameters, focus on the dynamic characteristics of the problem, and address rapid changes in the properties of the services and network appear to be among the most important issues that must be investigated and addressed. In this paper, utilizing a systematic literature review, important questions that can be raised about the research performed in addressing the above-mentioned problem have been extracted and put forth. Then, by dividing the research into four main groups based on the problem-solving approaches and identifying the investigated quality of service parameters, intended objectives, and developing environments, beneficial results and statistics are obtained that can contribute to future research.     

Online algorithms for advance resource reservations

We consider the problem of providing QoS guarantees to Grid users through advance reservation of resources. Advance reservation mechanisms provide the ability to allocate resources to users based on agreed-upon QoS requirements and increase the predictability of a Grid system, yet incorporating such mechanisms into current Grid environments has proven to be a challenging task due to the resulting resource fragmentation. We use concepts from computational geometry to present a framework for tackling the resource fragmentation, and for formulating a suite of scheduling strategies. We also develop efficient implementations of the scheduling algorithms that scale to large Grids. We conduct a comprehensive performance evaluation study using simulation, and we present numerical results to demonstrate that our strategies perform well across several metrics that reflect both user- and system-specific goals. Our main contribution is a timely, practical, and efficient solution to the problem of scheduling resources in emerging on-demand computing environments.     

A PSO-based intelligent service dispatching mechanism for customer expectation management

In the era of experience economy, service providers have to provide customers with high quality service experience in order to attract more customers and achieve higher customer satisfaction. Managing customer expectation is a critical approach for service providers to consider. Although customer expectation has been discussed across different research disciplines, to our knowledge, there is still no systematical and feasible way to apply customer expectation management into real environments. This study attempts to establish an intelligent service dispatching mechanism by using particle swarm optimization for customer expectation management. This mechanism can help service providers design and deliver satisfactory service experience to customers. In order to evaluate the effectiveness and robustness of this mechanism, this study employs micro- and macro-simulation experiments to confer and analyze its performance. The simulation results show service providers can gain benefit and raise customer satisfaction by managing customer expectation during service experience delivery. Meanwhile, customers can also receive memorable experiences and have positive responses to service providers and other customers. Consequently, a high performance ecosystem within service providers and customers can be formed.     

云服务安全性与可靠性的浅析

随着互联网的不断发展盛行,人类社会进入信息化时代.众多先进的信息技术不断被人们应用于生活的各个领域,它们不仅使人们的生活得到了很大改善,为人们的生活提供了很多便利之处,而且让网络技术得到了更广泛地发展、应用.然而,云服务在被人们使用的过程中出现了很多用户信息遗失和泄露等安全风险,云服务的安全性和可靠性受到人们的质疑.本文通过对云服务的安全性和可靠性进行思考,并借由学校云服务的运用探究云服务未来的发展.     

Disaster avoidance mechanism for content-delivering service

Many software applications have been developed on client-server and web-based architectures, with client software installed in numerous clerks’ devices spread over the whole of Taiwan along the hierarchical organization of large-scaled service companies. The damage for a large-scaled service company would be caused by an inconsistent system, in which client software fails to receive updated content causing loss of emergency calls and possibility of recovery. Therefore, a reliable content-delivering service is needed for such a large-scaled service company to ensure system consistency whenever a disaster occurs. This study analyses the error situations of a proposed content-delivering service that has been implemented in a large-scaled company in Taiwan. Moreover, its disaster avoidance mechanism provides a reliability model with the waiting-time distribution of disconnected links. The proposed disaster avoidance mechanism prevents damage from terminating operations of a company caused by disasters, such as earthquakes, tsunamis, nuclear plant explosions or wars. Empirical results demonstrate that the proposed design run on 19 servers distributes content with less than 3.4 content-delivery failures per million hours.     

A novel resource allocation mechanism for live cloud-based video streaming service

With the recent emergence of cloud computing, growing numbers of clients are using online cloud services through the Internet such as video streaming service. The rent costs of cloud service providers increase when the resource utilizations of the cloud-servers are not well. Therefore, resource allocation is a crucial problem for cloud data centers. The resource allocation problem is an NP-hard problem. This paper proposes a novel cloud resource allocation mechanism based on a winning strategy for a Nim game. This mechanism offers all clients an effective number of running cloud servers, and allocates cloud resources rapidly and effectively by using a pre-pairing approach. The proposed mechanism does not require searching for remaining resources of the running cloud server; hence, it can reduce the time taken to arrange resources. The experimental results show that the proposed mechanism can improve utilization of cloud servers and reduce the rent costs of the cloud service providers. The proposed mechanism can reach the utilization of cloud servers by as much as 99.96 %. The proposed mechanism is approximately 9 % more efficient than the market-based grid resource allocation algorithm, and 19 % more efficient than the modified best fit decreasing algorithm.

     

A token-bucket based notification traffic control mechanism for IMS presence service

Presence is a service that allows a user to be informed about the specified state of another user. Presence service has become a key enabler for next-generation applications such as instant messaging, push-to-talk and web2.0. However, recent studies show that the notification traffic of presence service causes heavy signaling load on IP multimedia subsystem (IMS) network. This paper introduced a token-bucket based notification traffic control (TNTC) mechanism, which is an application layer solution deployed at the presence server. The TNTC aims at upgrading valid access probability while controlling the notification traffic. A mathematical model of a queuing system is proposed to describe TNTC. We analyzed its main probability features and investigated the effects of different parameters on the performance of TNTC. Extensive simulations verified that TNTC can effectively control notification traffic and perform better than the existing schemes in terms of valid access probability and update arrival rate.     

Advance reservations for service-aware GMPLS-based optical networks

In service-oriented networks, cooperation between users, applications and network tends to come closer. With this objective, new architectures arise to cope with the upcoming demands. Of great importance is the definition of the proper interfaces and network services. One of these new services is known as the Advance Reservation Service. This service allows prior reservation of network resources in order to provide guaranteed client connections. The introduction of advance reservations in heterogeneous transport networks imposes the need to find new mechanisms that consider temporal characteristics of scheduled connections and their impact on immediate connections. In this paper, we investigate these issues, propose novel algorithms to improve overall network performance, and describe the implementation carried out over the ASON/GMPLS CARISMA testbed.     

Economic production quantity models for deteriorating items with price- and stock-dependent demand

Large piles of consumer goods displayed in a supermarket are often associated with on sale items to induce more sales and profits. In this paper, we first establish an economic production quantity (or EPQ) model for deteriorating items when the demand rate depends not only the on-display stock level but also the selling price per unit. In addition, we impose a ceiling on the number of on-display stocks because too much stock leaves a negative impression on the buyer and the amount of shelf/display space is limited. We then provide the necessary conditions to determine an optimal solution that maximizes profits for the EPQ model. Finally, sensitivity analysis is applied on the parameter effects of the optimal price and production run time.     

Cloud service selection using cloud service brokers: approaches and challenges

Cloud computing users are faced with a wide variety of services to choose from. Consequently, a number of cloud service brokers (CSBs) have emerged to help users in their service selection process. This paper reviews the recent approaches that have been introduced and used for cloud service brokerage and discusses their challenges accordingly. We propose a set of attributes for a CSB to be considered effective. DifFerent CSBs' approaches are classified as either single service or multiple service models. The CSBs are then assessed, analyzed, and compared with respect to the proposed set of attributes. Based on our studies, CSBs with multiple service models that support more of the proposed effective CSB attributes have wider application in cloud computing environments.     

Cloud federation in a layered service model

We show how a layered Cloud service model of software (SaaS), platform (PaaS), and infrastructure (IaaS) leverages multiple independent Clouds by creating a federation among the providers. The layered architecture leads naturally to a design in which inter-Cloud federation takes place at each service layer, mediated by a broker specific to the concerns of the parties at that layer. Federation increases consumer value for and facilitates providing IT services as a commodity. This business model for the Cloud is consistent with broker mediated supply and service delivery chains in other commodity sectors such as finance and manufacturing. Concreteness is added to the federated Cloud model by considering how it works in delivering the Weather Research and Forecasting service (WRF) as SaaS using PaaS and IaaS support. WRF is used to illustrate the concepts of delegation and federation, the translation of service requirements between service layers, and inter-Cloud broker functions needed to achieve federation.     

分布式资源的Web服务组合机制

单个资源的服务往往不能满足任务需求,而多个服务的组合却可以派生出新的服务。为此,模拟迷宫求解的思路,设计了一套通用服务组合算法,将分布式资源提供的可用服务看作为迷宫中的条条道路,而将服务组合方案看作为连接迷宫入口和出口的一条通路,通过服务与服务、服务与需求之间的功能性关联,自动生成满足任务需求的服务组合方案。模拟实验验证了方法的有效性。     

VoWLAN中基于TDMA的QoS机制的研究

针对无线局域网语音应用缺乏可靠服务质量的情况,提出了一种基于时分多址接入的服务质量新机制。该机制采用了IEEE802.15.3无线个域网的中心调度方式,使用时分多址接入机制控制节点接入信道。并在平均接入时延、时延抖动和分组丢失率三方面对IEEE802.11b、IEEE802.11e和新方案三者的性能进行了对比。仿真结果表明,IEEE802.11b性能最差,新机制的性能在平均接入时延和分组丢失率方面比IEEE802.11e分别改善了20%和50%左右。     

云制造环境下基于可信评价的云服务选择

针对云制造环境下因存在大量功能相同或相似的制造云服务而导致用户很难获得合适云服务的问题,提出了一种基于可信评价的制造云服务选择方法。对问题进行了抽象,将可靠性、可用性、时效性、价格和诚信度纳入可信特征集,并考虑评价时间、评价者的诚信度对可信值的影响,采用加权平均的方法计算制造云服务的整体可信度;在此基础上,综合考虑制造云服务的功能、任务负载、当前状态和物理距离等因素,通过匹配功能、任务负载和价格,并结合可信评价值来指导云服务的选择。仿真结果表明,所提方法能够有效地识别云制造环境下的制造云服务实体,可提高交易活动的成功率,满足用户的功能需求和非功能需求。