Session based access control in geographically replicated Internet services

Performance critical services over Internet often rely on geographically distributed architectures of replicated servers. Content Delivery Networks (CDN) are a typical example where service is based on a distributed architecture of replica servers to guarantee resource availability and proximity to final users. In such distributed systems, network links are not dedicated, and may be subject to external traffic. This brings up the need to develop access control policies that adapt to network load changing conditions. Further, Internet services are mainly session based, thus an access control support must take into account a proper differentiation of requests and perform session based decisions while considering the dynamic availability of resources due to external traffic.In this paper we introduce a distributed architecture with access control capabilities at session aware access points. We consider two types of services characterized by different patterns of resource consumption and priorities. We formulate a Markov Modulated Poisson Decision Process for access control that captures the heterogeneity of multimedia services and the variable availability of resources due to external traffic. The proposed model is optimized by means of stochastic analysis, showing the impact of external traffic on service quality. The structural properties of the optimal solutions are studied and considered as the basis for the formulation of heuristics. The performance of the proposed heuristics is studied by means of simulations, showing that in some typical scenario they perform close to the optimum.     

Adapting multimedia Internet content for universal access

Content delivery over the Internet needs to address both the multimedia nature of the content and the capabilities of the diverse client platforms the content is being delivered to. We present a system that adapts multimedia Web documents to optimally match the capabilities of the client device requesting it. This system has two key components. 1) A representation scheme called the InfoPyramid that provides a multimodal, multiresolution representation hierarchy for multimedia. 2) A customizer that selects the best content representation to meet the client capabilities while delivering the most value. We model the selection process as a resource allocation problem in a generalized rate distortion framework. In this framework, we address the issue of both multiple media types in a Web document and multiple resource types at the client. We extend this framework to allow prioritization on the content items in a Web document. We illustrate our content adaptation technique with a web server that adapts multimedia news stories to clients as diverse as workstations, PDA's and cellular phones     

Achieving concurrency in cloud-orchestrated Internet of Things for resource sharing through multiple concurrent access

Cloud-orchestrated Internet of Things (IoT) facilitates proper utilization of network resources and placating user demands in smart communications. Multiple concurrent access (MCA) techniques designed for cloud-assisted communication helps to achieve better resource sharing features with fault tolerance ability. A multi-objective resource allocation and sharing (RAS) for balancing MCA in cloud-orchestrated IoT is presented in this article. The RAS constraints are modeled through linear programming (LP) as an optimization approach. The constraints are resolved using genetic representations (GR) for reducing the unserviced requests and failed resource allocations. Conventional genetic stages are inherited by the LP model to solve resource allocation and access issues reducing latency. The combined LP and GR jointly resolve resource allocation and MCA stagnation in cloud network. A fair outcome of LP-GR is estimation using the metrics response latency, resource utilization, request handled, and average latency.     

Narrowing the gap to Internet access

As the Internet evolves, the gap widens between information “haves” and “havenots”, between highly developed nations and those where it is said that two billion people are yet to make their first telephone call. Not surprisingly, in underdeveloped nations where a telephone is rare, access to the Internet is even rarer. As technologists, what can we do to ameliorate this problem? At the practical level, we can't do much for the throngs of illiterate older folks who have barely enough food to eat in those underdeveloped countries. But, if we handle it right, there may be much that the Internet can do for their children. In the longer term, providing their children with Internet access may also benefit our children. The wars of today are primarily among the poorest countries of the world, and small country wars have a historical propensity to act as tinder to ignite larger conflagrations. The author believes that technologists can offer access to the world's information to all the bright kids around the world and accelerate the process of global educational equalization     

Binary vote assignment on a grid for efficient access of replicated data

Data replication can be used to improve the availability of data in a distributed database system. In such a system, a mechanism is required to maintain the consistency of the replicated data. Grid structure (GS) technique based on quorum is one of the latest solutions for performing this while providing a high availability of the system. It was shown in the previous study, that it still requires a bigger number of copies be made available to construct a quorum. So it is not suitable for the large systems. In this paper, we propose a technique called the binary vote assignment on grid (BVAG) technique by considering only neighbors have the replicated data. In comparison to the GS technique, BVAG requires lower communication cost for an operation, while providing higher data availability, which is preferred for large systems.     

Technology acceptance model: A replicated test using TETRAD

The technology acceptance model proposes that ease of use and usefulness predict the acceptance of information technology. Since its inception, the model has been widely applied in understanding user acceptance behavior. In a recent study on e‐commerce applications, we surprisingly found that the model was validated when tested in isolation but failed within the larger nomological network. In this paper, we applied TETRAD III to explore the issue. As expected, we discovered two spurious associations in the model and fundamentally challenge its validity and hundreds of related studies. © 2009 Wiley Periodicals, Inc.     

A flexible security system for using Internet content

The Internet and World Wide Web have introduced a powerful new way to acquire content. Previously, users had to either buy or order content on coded disks. They can now download executable code and applications directly. From the users' viewpoint, this decreases the amount of software stored on their machines. It also lets content providers customize applications by combining different vendors' content. Downloading content from the Internet brings risks: content that appears reputable may be malicious, given system access it can damage or destroy data. To contend with this risk, the author developed FlexxGuard, a flexible interpreter that dynamically derives protection domains and uses those domains to authorize content operations     

Pricing Internet access

As a rule, economic facts are often the equivalent of a cold shower. The plain fact is that not many internet firms were profitable at any time in the last five years. The list of unprofitable companies (and spectacular investment failures) is embarrassingly long, including Amazon, AT&T Broadband, E-Toys, Dr. Koop, and too many other dot-coms to mention. Indeed, positive profitability was so rare that we all know the names of firms that achieved it: Cisco, Yahoo, E-Bay, and AOL (if you count them as an Internet company). So I am struck by the comparative success of one general class of companies that continues to collect revenue, compete vigorously, achieve mass-market status, and not implode in spite of frequent restructuring. I refer to Internet service providers, or ISPs for short. How in the world can hundreds of these firms survive in this market over so many years-particularly in light of free alternatives, such as Netzero? What pricing mechanisms do access providers use to collect revenue? Why do these mechanisms work? More to the point, what do these mechanisms tell us about the source of sustainable economic value in Internet activity?     

Internet access to a home area network

The AutoHan project implements a self-configuring software architecture for home area networks that offers an XML-based registry and HTTP-based service. The article begins by introducing the low-level architectures of the AutoHan project that enable different networking technologies to interoperate and define one logical IP network. It then describes the two core services that enable resources to export, discover and interoperate with AutoHan by using these low-level architectures. Finally, the article discusses naming and addressing issues for Internet access and shows how XML and HTTP allowed extension of the system to support Internet access through IHan (Internet home area network)     

A memory access model for highly-threaded many-core architectures

A number of highly-threaded, many-core architectures hide memory-access latency by low-overhead context switching among a large number of threads. The speedup of a program on these machines depends on how well the latency is hidden. If the number of threads were infinite, theoretically, these machines could provide the performance predicted by the PRAM analysis of these programs. However, the number of threads per processor is not infinite, and is constrained by both hardware and algorithmic limits. In this paper, we introduce the Threaded Many-core Memory (TMM) model which is meant to capture the important characteristics of these highly-threaded, many-core machines. Since we model some important machine parameters of these machines, we expect analysis under this model to provide a more fine-grained and accurate performance prediction than the PRAM analysis. We analyze 4 algorithms for the classic all pairs shortest paths problem under this model. We find that even when two algorithms have the same PRAM performance, our model predicts different performance for some settings of machine parameters. For example, for dense graphs, the dynamic programming algorithm and Johnson’s algorithm have the same performance in the PRAM model. However, our model predicts different performance for large enough memory-access latency and validates the intuition that the dynamic programming algorithm performs better on these machines. We validate several predictions made by our model using empirical measurements on an instantiation of a highly-threaded, many-core machine, namely the NVIDIA GTX 480.     

A fault-tolerant algorithm for replicated data management

We examine the tradeoff between message overhead and data availability that arises in the design of fault-tolerant algorithms for replicated data management in distributed systems. We propose a property called asymptotically high resiliency which is useful for evaluating the fault-tolerance of replica control algorithms and distributed mutual exclusion algorithms. We present a new algorithm for replica control that can be tailored (through a design parameter) to achieve the desired balance between low message overhead and high data availability. Further, we show that for a message overhead of O(√(Nlog N)), our algorithm can achieve asymptotically high resiliency     

A performance model of a design for a minimally replicated distributed database for database-driven telecommunications services

In intelligent networking telecommunication services such as free-phone and various personal communications services, the dialed number corresponds to the identity of the called party rather than to the called party's physical location. The dialed number must therefore be converted to a routable telephone number during call setup. This accomplished by querying a database. If the query is successful, its result is a routable number which is passed to the switch at which the call originates so that the call may be completed. A database maintained solely at a single node may not be sufficient to support the large capacity, reliability, and rapid processing requirements of this service. However, these requirements may be met by replicating and distributing the database instead.Replication and distribution induce problems of consistency, concurrency, and load balancing. We describe and present a performance model of a scheme for replicating customer profiles efficiently. To spread the query transaction load, the database and its replicates could be distributed over a set of geographically distinct nodes. The database would be partitioned into as many disjoint fragments as there are nodes. Each fragment would be stored at two of the nodes, subject to the constraint that no pair of subsets would be stored at more than one node. This constraint ensures that the load which would have been carried by a failed node is spread to two other nodes instead of one, thus reducing the risk of overload in case of failure. We also use a performance analysis to arrive at heuristics for routing transactions within the database which attempt to minimize the query and update response times. For a particular implementation, the analysis suggests that READ or query transactions should be routed to the least loaded node of those holding the fragment of interest. By contrast, when strict locking of all copies is required while performing an update, WRITE or update transactions which are initiated at one node and repeated at the other should be routed to the more heavily loaded of the nodes to minimise overall response time. Recommended by: Amit ShethA shorter version of this paper was presented at the 8th ITC Specialist Seminar on Universal Personal Telecommunications held at Santa Margherita Ligure, Italy, in October 1992.     

A concurrent engineering-oriented design database representation model

A concurrent engineering-oriented design database representation model (CE-DDRM) is introduced in this research for supporting various life-cycle aspects in concurrent design. In this model, concepts and behaviors of different design database modeling components, including entities, properties, relationships, tasks, and specifications, are defined at meta-class level. Design database is modeled at two different levels, class level and instance level, representing generic design libraries and special design cases, respectively. A Web-based system architecture is proposed to model distributed design database and allow team-members for different product development life-cycle aspects at different locations to access the design database. This newly introduced approach provides the foundation for developing the next generation CAD systems with concurrent engineering functions.     

A model of dynamical concurrent program execution

Dynamical concurrent execution makes it possible to adapt programs for their execution on computing environments with parallel architecture. In the paper, a formal model of dynamical concurrent execution of programs written in functional style is presented. The model is proven to possess a feature that guarantees correctness of concurrent execution.     

基于区块链的物联网访问控制框架

物联网（IoT）中入网设备的海量性、动态性和设备轻量级是内在联系并同时存在的特征。为了同时满足上述三个特征,提出一种基于区块链的IoT访问控制（BBIAC）框架。首先提出了该框架下的BBIAC模型,在IoT授权过程中引入属性的概念以满足模型对海量性的支持;而区块链自身的分布式结构和身份认证方式为该模型提供了动态性的支持;同时,区块链自身提供的安全性和多机构信任使BBIAC模型可以将需要大规模计算和存储的部分部署在区块链中,使该模型支持轻量级的IoT设备。接着,介绍了BBIAC模型完整的工作流程。然后,通过着色Perti网（CPN）对BBIAC模型进行形式化的安全性评估,证明了BBIAC模型的安全性。实验结果表明,BBIAC适用于具有海量性、动态性和设备轻量级特征的IoT环境。     

User-centric mobility management for multimedia content access

Current mobility protocols and architectures are mainly targeted to devices or applications and they usually lack the ability to support user-centric paradigms; moreover, they usually face a single aspect of the problem, i.e., terminal handover or session mobility. Full mobility support is only available to specific applications or protocols (e.g., SIP) but these approaches do not exploit all facilities for movement detection at the network/link layers and do not allow to use the same framework for different applications. This paper proposes a generic mobility framework for terminal handover and session migration. It pursues the user-centric paradigm and builds a cross-layer architecture, yielding to a high level of generality, applicability and flexibility. Unlike other approaches, it does not require any modification in correspondent peers and works with a minimal network infrastructure. Software implementations are described for two representative real-time multimedia applications, i.e., media streaming and interactive conference. The effectiveness of the framework was analyzed by means of both performance measurements in local and Internet testbeds and user evaluation during a live demo conducted at a national science exhibition.     

Progressive content access to databases of JPEG-compressed images

Progressive content access provides a mode that allows a coarse version of an image being viewed at a lower computing cost and then gradually refined by subsequent resolution enhancement if required. This proves extremely useful when millions of compressed images and video sequences need to be browsed manually or processed in pixel domain, saving the cost and removing the necessity of full decompression. Such a progressive content access algorithm suitable for all discrete-cosine-transform-based (DCT-based) JPEG and MPEG-compressed files is proposed here. First a theoretical model in approximation of cosine function used in inverse discrete cosine transform (IDCT) with various orders is developed. Following that a progressive content access algorithm, which comprehends both the successive approximation and the spectral selection, is proposed. Further analysis and experiments are reported to show that our proposed algorithm saves computational cost in comparison with JPEG full decompression. Extensive experiments also support that the proposed algorithm achieves encouraging peak signal-to-noise ratio (PSNR) values for reconstructed images even with lower order approximation.     

基于区块链与边缘计算的物联网访问控制模型

边缘计算的出现扩展了物联网（IoT）云-终端架构的范畴,在减少终端设备海量数据的传输和处理时延的同时也带来了新的安全问题。针对IoT边缘节点与海量异构设备间的数据安全和管理问题,并考虑到目前区块链技术广泛应用于分布式系统中数据的安全管理,提出基于区块链与边缘计算的IoT访问控制模型SC-ABAC。首先,提出集成边缘计算的IoT访问控制架构,并结合智能合约和基于属性的访问控制（ABAC）提出并设计了SC-ABAC;然后,给出工作量证明（PoW）共识算法的优化和SC-ABAC的访问控制管理流程。实验结果表明,所提模型对区块连续访问下的耗时随次数呈线性增长,连续访问过程中央处理器（CPU）的利用率稳定,安全性良好。本模型下仅查询过程存在调用合约的耗时随次数呈线性增长,策略添加和判断过程的耗时均为常数级,且优化的共识机制较PoW每100块区块共识耗时降低约18.37个百分点。可见,该模型可在IoT环境中提供去中心化、细颗粒度和动态的访问控制管理,并可在分布式系统中更快达成共识以确保数据一致性。