Conformance analysis in networks with service level agreements

To achieve some level of Quality of Service (QoS) assurance, a network usually has Service Level Agreements (SLAs) with its users and neighboring domains, which describe the QoS level that the service provider is committed to provide, and the specification of traffic that users or neighboring domains are allowed to send. An interesting and important question arises as to whether a flow is still conformant to its original traffic specification after crossing the network since it may interact with other flows within the network. In this paper, we study analytically the extent to which a flow and an aggregate of flows become non-conformant through an analysis of the stochastic burstiness increase of flows after crossing a per-flow scheduling network and an aggregate scheduling network . The stochastic behavior of a server in aggregate scheduling networks is also studied to determine the conformance deterioration of individual flows, which provides the theoretical conformance deterioration bound and provides useful results for conformance analysis in an aggregate scheduling network with general topology. Our theoretical results are verified by extensive simulations.     

Optimal precomputation for mapping service level agreements in grid computing

A complicated task running on the grid system is usually made up of many services, each of which typically offers a better service quality at a higher cost. Mapping service level agreements (SLAs) optimally is to find the most appropriate quality level for each service such that the overall SLA of a task is achieved at the minimum cost. This paper considers mapping the execution time SLA in the case of the discrete cost function, which is an NP-hard problem. Due to the high computation of mapping SLAs, we propose a precomputation scheme that makes the selection of each individual service level in advance for every possible SLA requirement, which can reduce the request response time greatly. We use a (1+ε)-approximation method, whose solution for any time bound is at most (1+ε) times of the optimal cost. Simulation results demonstrate the superiority of our method compared with others.     

The WSLA Framework: Specifying and Monitoring Service Level Agreements for Web Services

We describe a novel framework for specifying and monitoring Service Level Agreements (SLA) for Web Services. SLA monitoring and enforcement become increasingly important in a Web Service environment where enterprise applications and services rely on services that may be subscribed dynamically and on-demand. For economic and practical reasons, we want an automated provisioning process for both the service itself as well as the SLA managment system that measures and monitors the QoS parameters, checks the agreed-upon service levels, and reports violations to the authorized parties involved in the SLA management process. Our approach to these issues is presented in this paper. The Web Service Level Agreement (WSLA) framework is targeted at defining and monitoring SLAs for Web Services. Although WSLA has been designed for a Web Services environment, it is applicable as well to any inter-domain management scenario, such as business process and service management, or the management of networks, systems and applications in general. The WSLA framework consists of a flexible and extensible language based on XML Schema and a runtime architecture comprising several SLA monitoring services, which may be outsourced to third parties to ensure a maximum of objectivity. WSLA enables service customers and providers to unambiguously define a wide variety of SLAs, specify the SLA parameters and the way they are measured, and relate them to managed resource instrumentations. Upon receipt of an SLA specification, the WSLA monitoring services are automatically configured to enforce the SLA. An implementation of the WSLA framework, termed SLA Compliance Monitor, is publicly available as part of the IBM Web Services Toolkit.     

面向服务的服务等级协议实现框架的研究

对面向运营支撑系统的服务等级协议（SLA）实现框架进行了研究,为了实现基于SLA驱动的下一代运营支撑系统的业务管理层的流程自动化,在WfMC工作流参考模型和面向服务框架的基础上,提出了基于工作流管理的服务等级协议实现框架,并采用面向服务架构（SOA）的商业处理执行语言（BPEL）,详细给出了基于该体系结构的SLA实现框架的应用实例。     

Managing a service system with social interactions: Stability and chaos

This paper investigates the dynamic behavior of a service system in terms of the arrival rate in the steady state under the influence of social interactions. Customers are backward looking and rational when making purchasing decisions. Existing customers’ re-purchasing decisions are based on their experienced utility – a function of the average waiting time and their expected utility. Potential customers are attracted through social interactions with existing customers. It is shown that the arrival rate of the system in the steady state can exhibit stability, periodic cycles, or chaos due to the effect of social interactions and customers’ purchasing behavior. Two examples based on an M/M/1 queueing system illustrate the role of social interactions and the effect of service rates on the stability of the arrival rate in the steady state. The result highlights the dynamical complexity of a simple service system under the impact of customers’ behavioral factors, or social interactions. It suggests a new perspective to managing service operations whereby social interactions may play a critical role in the fluctuations of demand.     

Service process control: a method to compare dynamic robustness of alternative service processes

This paper contributes to the service engineering field by developing a procedure to compare the dynamic robustness of alternative service delivery processes. The procedure adapts an existing method for comparing the dynamic robustness of chemical process control systems. It has four steps: (a) characterisation of each type of uncertainty that affects the service plant; (b) Monte Carlo computer simulation of the process flowchart to determine how the service process responds to different combinations of uncertainties; (c) calculation of a quality index for each combination of uncertainties; and (d) plotting of a frequency distribution of these indices. The tighter the resulting distribution, the more robust the system. The procedure can be used to evaluate the effects of design and control changes in the service delivery process. To demonstrate the procedure, a modification to a hospital patient-treatment process is evaluated.     

A pricing approach for bandwidth allocation in differentiated service networks

We present a decentralized auction-based scheme for bandwidth allocation and pricing in a differentiated service-based network. Different classes of clients provide their own expected bandwidth price and required amount of bandwidth. A service provider decides the admission price and differentiated service provided for each class of clients. We introduce mathematical formulations and provide a solution approach to maximize the service provider's revenue. For a single bottleneck link case, a polynomial-time algorithm is developed to obtain an optimal solution. For a multiple bottleneck link case, a heuristic algorithm is developed to solve the problem. The effectiveness of our solution approach is validated by simulation results, which compare our algorithms against the traditional flat-rate pricing approach.     

A survey on fraud and service misuse in voice over IP (VoIP) networks

The migration from circuit-switched networks to packet-switched networks necessitates the investigation of related issues such as service delivery, QoS, security, and service fraud and misuse. The latter can be seen as a combination of accounting and security aspects. In traditional telecommunication networks, fraud accounts for annual losses at an average of 3%–5% of the operators’ revenue and still increasing at a rate of more than 10% yearly. It is also expected that in VoIP networks, the situation will be worse due to the lack of strong built-in security mechanisms, and the use of open standards. This paper discusses the fraud problem in VoIP networks and evaluates the related available solutions.     

OPQR-G: algorithm for efficient QoS partition and routing in multiservice IP networks

This paper considers the combined problem of optimal QoS partition and routing (problem QPQR-G) for a QoS framework in which a performance dependent cost function is associated with each network element and the QoS metric is additive (e.g. delay, jitter). This problem has been addressed in the context of unicast connections and multicast trees only. Here we consider the problem for a more general case of a multicommodity flow network. Also, it is assumed that the performance dependent cost functions are non-increasing and are of general integer type. The goal is to determine primary paths between the origin and destination (OD) pairs and QoS partitions on the links so that the overall cost in the network is minimised while all OD pair QoS requirements are satisfied. As the problem is NP-complete, we concentrate on the development of an efficient heuristic algorithm. In addition, two LP-based algorithms were developed, that use the optimisation tool ILOG™ CPLEX 7.1 LP for solving the problem OPQR-G. The numerical results obtained for various test network scenarios are very close to the optimal. The problem addressed in this paper provides the basis for the solution of many interesting and practical engineering problems, such as dimensioning and admission control/resource reservation in IP networks that support service differentiation.     

Static and dynamic minimum energy broadcast problem in wireless ad-hoc networks: A PSO-based approach and analysis

In this paper, we address the minimum energy broadcast (MEB) problem in wireless ad-hoc networks (WANETs). The researches in WANETs have attracted significant attentions, and one of the most critical issues in WSNs is minimization of energy consumption. In WANETs the packets have to be transported from a given source node to all other nodes in the network, and the objective of the MEB problem is to minimize the total transmission power consumption. A hybrid algorithm based on particle swarm optimization (PSO) and local search is presented to solve the MEB problem. A power degree encoding is proposed to reflect the extent of transmission power level and is used to define the particle position in PSO. We also analyze a well-known local search mechanism, r-shrink, and propose an improved version, the intensified r-shrink. In order to solve the dynamic MEB problem with node removal/insertion, this paper provides an effective simple heuristic, Conditional Incremental Power (CIP), to reconstruct the broadcast network efficiently. The promising results indicate the potential of the proposed methods for practical use.     

Overlay network resource allocation using a decentralized market-based approach

We present a decentralized market-based approach to resource allocation in a heterogeneous overlay network. This resource allocation strategy dynamically assigns resources in an overlay network to requests for service based on current system utilization, thus enabling the system to accommodate fluctuating demand for its resources. Our approach is based on a mathematical model of this resource allocation environment that treats the allocation of system resources as a constrained optimization problem. From the solution to the dual of this optimization problem, we derive a simple decentralized algorithm that is extremely efficient. Our results show the near optimality of the proposed approach through extensive simulation of this overlay network environment. The simulation study utilizes components taken from a real-world middleware application environment and clearly demonstrates the practicality of the approach in a realistic setting.     

工业以太网自动IP地址服务解决方案

工业以太网IP地址分配的关键问题是实现替换设备的IP地址自动分配。在深入分析BOOTP和DHCP协议的工作原理及其优缺宝竺基础上，提出了一种基于BOOTP、SNMP协议并适合于工业以太网自动IP地址分配和服务的解决方案，并对系统实现的各关键环节进行了讨论。     

COCOA: COnversation-based service COmposition in pervAsive computing environments with QoS support

Pervasive computing environments are populated with networked services, i.e., autonomous software entities, providing a number of functionalities. One of the most challenging objectives to be achieved within these environments is to assist users in realizing tasks that integrate on the fly functionalities of the networked services opportunely according to the current pervasive environment. Towards this purpose, we present COCOA, a solution for COnversation-based service COmposition in pervAsive computing environments with QoS support. COCOA provides COCOA-L, an OWL-S based language for the semantic, QoS-aware specification of services and tasks, which further allows the specification of services and tasks conversations. Moreover, COCOA provides two mechanisms: COCOA-SD for the QoS-aware semantic service discovery and COCOA-CI for the QoS-aware integration of service conversations towards the realization of the user task’s conversation. The distinctive feature of COCOA is the ability of integrating on the fly the conversations of networked services to realize the conversation of the user task, by further meeting the QoS requirements of user tasks. Thereby, COCOA allows the dynamic realization of user tasks according to the specifics of the pervasive computing environment in terms of available services and by enforcing valid service consumption.     

On improving bandwidth assurance in AF-based DiffServ networks using a control theoretic approach

The assured forwarding (AF) based service in a differentiated services (DiffServ) network fails to provide bandwidth assurance among competing aggregates under certain conditions, for example, where there exists a large disparity in the round-trip times, packet sizes, or target rates of the aggregates, or there exist non-adaptive aggregates. Several mechanisms have been proposed in order to address the problem of providing bandwidth assurance for aggregates, using only the knowledge gathered at ingress routers. In this paper, we present a control theoretic approach to analyze these mechanisms and explore the reasons when they fail to achieve bandwidth assurance under some circumstances. Then we propose a simple but robust controller for this problem, namely, the variable-structure adaptive CIR threshold (VS-ACT) mechanism. We validate the analysis and demonstrate that VS-ACT outperforms several other mechanisms proposed in the literature over a wide range of network dynamics through extensive simulations.     

MABP: an optimal resource allocation approach in data center networks

In data center networks, resource allocation based on workload is an effective way to allocate the infrastructure resources to diverse cloud applications and satisfy the quality of service for the users, which refers to mapping a large number of workloads provided by cloud users/tenants to substrate network provided by cloud providers. Although the existing heuristic approaches are able to find a feasible solution, the quality of the solution is not guaranteed. Concerning this issue, based on the minimum mapping cost, this paper solves the resource allocation problem by modeling it as a distributed constraint optimization problem. Then an efficient approach is proposed to solve the resource allocation problem, aiming to find a feasible solution and ensuring the optimality of the solution. Finally, theoretical analysis and extensive experiments have demonstrated the effectiveness and efficiency of our proposed approach.     

Improving service matching and selection in ubiquitous computing environments: a user study

In large ubiquitous computing environments it is hard for users to identify and activate the electronic services that match their needs. This user study compares the newly developed service matcher system with a conventional system for identifying and selecting appropriate services. The study addresses human factors issues such as usability, trust and service awareness. With the conventional system users have to browse a hierarchical list of currently available services and activate the service that they think satisfies their current needs. With the service matcher users just enter their current need using natural language, after which a wizard, emulating an existing service matcher algorithm, searches for and activates a matching service based on the given need and the users’ location and gaze direction. This study shows that with the hierarchical list, only 66% of the tasks are solved correctly, and females score significantly worse than males. With the service matcher, the performance increases significantly to 84% correctly performed tasks and the gender difference disappears.     

DynMAC: A resistant MAC protocol to coexistence in wireless sensor networks

The growth of mobile and ubiquitous computing has increased the demand for wireless communications, which in turn raises interference levels and spectrum pollution, causing problems of network coexistence. The coexistence assurance between these devices and wireless sensor networks is a big challenge. This paper proposes a new medium access protocol, DynMAC (Dynamic MAC), which uses mechanisms of dynamic channel reconfiguration, recovery from lost links and reconfiguration of transmission parameters based on the properties of the cognitive radios, to deal with this problem. Simulations and experiments using a real WSN testbed, were performed to validate our protocol. Results show that the proposed mechanisms solve the WSN configuration problems, in noisy and interference environments, and enable the coexistence with different networks and devices operating in the same frequency spectrum, while maintaining application requirements in critical deployment scenarios.