Dynamic configuration management in reliable distributed real-timeinformation systems

A new architecture for large-scale information systems is presented. The original aspects of the architecture are mainly: (1) the time-triggered, message-triggered object (TMO) structuring of the middleware and the application software of distributed real-time information systems; and (2) the dynamic configuration management subsystem (DCMS), based on the supervisor-based network surveillance (SNS) scheme. The positive impacts of this TMO structuring on maintainability and service interruption bounds are first discussed, with distributed replicated information service systems and other systems as examples. The main discussion is on the DCMS architecture. As a component of the DCMS, the network surveillance (NS) subsystem enables fast learning, by each interested fault-free node in the system, of the faults or repair completion events occurring in other parts of the system. Currently, concrete real-time NS schemes that are effective in distributed systems based on point-to-point network architectures are scarce. The SNS scheme presented in this paper is a semi-centralized real-time NS scheme which is effective in a variety of point-to-point networks. This scheme is highly scalable. An efficient implementation model for the SNS scheme is presented that can be easily adapted to various commercial operating system kernels. This paper also presents a formal analysis of the SNS scheme, on the basis of the implementation model, to obtain its strongly competitive tight bounds on the fault detection latency. Finally, some DCMS implementation issues are discussed that remain to be addressed in future research     

MOSAIC: Declarative platform for dynamic overlay composition

Overlay networks create new networking services using nodes that communicate using pre-existing networks. They are often optimized for specific applications and targeted at niche vertical domains, but lack interoperability with which their functionalities can be shared. Mosaic is a declarative platform for constructing new overlay networks from multiple existing overlays, each possessing a subset of the desired new network’s characteristics.This paper focuses on the design and implementation of Mosaic: composition and deployment of control and/or data plane functions of different overlay networks, dynamic compositions of overlay networks to meet changing application needs and network conditions, and seamless support for legacy applications. Mosaic overlays are specified using Mozlog, a new declarative language for expressing overlay properties independently from their particular implementation or underlying network.Mosaic is validated experimentally using compositions specified in Mozlog in order to create new overlay networks with compositions of their functions: the i3 indirection overlay that supports mobility, the resilient overlay network (RON) overlay for robust routing, and the Chord distributed hash table for scalable lookups. Mosaic uses runtime composition to simultaneously deliver application-aware mobility, NAT traversal and reliability. We further demonstrate Mosaic’s dynamic composition capabilities by Chord switching its underlay from IP to RON at runtime.Mosaic’s benefits are obtained at a low performance cost, as demonstrated by measurements on both a local cluster environment and the PlanetLab global testbed.     

Design, Implementation, and Evaluation of the Remos Network Monitoring System

Remos provides resource information to distributed applications. Its design goals of scalability, flexibility, and portability are achieved through an architecture that allows components to be positioned across the network, each collecting information about its local network. To collect information from different types of networks, Remos provides several Collectors that use different technologies, including SNMP and benchmarking. By matching the Collector to the particular network environment and by providing an architecture for distributing the output of these collectors across all querying environments, Remos collects appropriately detailed information at each site and distributes this information where needed in a scalable manner. Remos has been implemented and tested in a variety of networks and is in use in a number of different environments.     

Declarative secure distributed information systems

We present a unified declarative platform for specifying, implementing, and analyzing secure networked information systems. Our work builds upon techniques from logic-based trust management systems and declarative networking. We make the following contributions. First, we propose the Secure Network Datalog (SeNDlog) language that unifies Binder, a logic-based language for access control in distributed systems, and Network Datalog, a distributed recursive query language for declarative networks. SeNDlog enables network routing, information systems, and their security policies to be specified and implemented within a common declarative framework. Second, we extend existing distributed recursive query processing techniques to execute SeNDlogprograms that incorporate secure communication via authentication and encryption among untrusted nodes. Third, we demonstrate the use of user-defined cryptographic functions for customizing the authentication and encryption mechanisms used for securing protocols. Finally, using a local cluster and the PlanetLab testbed, we perform a detailed performance study of a variety of secure networked systems implemented using our platform.     

Capability-Aware Information Aggregation in Peer-to-Peer Grids

Information aggregation is the process of summarizing information across the nodes of a distributed system. We present a hierarchical information aggregation system tailored for Peer-to-Peer Grids which typically exhibit a high degree of volatility and heterogeneity of resources. Aggregation is performed in a scalable yet efficient way by merging data along the edges of a logical self-healing tree with each inner node providing a summary view of the information delivered by the nodes of the corresponding subtree. We describe different tree management methods suitable for high-efficiency and high-scalability scenarios that take host capability and stability diversity into account to attenuate the impact of slow and/or unstable hosts. We propose an architecture covering all three phases of the aggregation process: Data gathering through a highly extensible sensing framework, data aggregation using reusable, fully isolated reduction networks, and application-sensitive data delivery using a broad range of propagation strategies. Our solution combines the advantages of approaches based on Distributed Hash Tables (DHTs) (i.e., load balancing and self-maintenance) and hierarchical approaches (i.e., respecting administrative boundaries and resource limitations). Our approach is integrated into our Peer-to-Peer Grid platform Cohesion. We substantiate its effectiveness through performance measurements and demonstrate its applicability through a graphical monitoring solution leveraging our aggregation system.     

A matrix grammar approach for automatic distributed network resource management

Network resource management is critical to ensure the security and optimal performance of distributed networks and information systems. Existing technologies are not capable of managing large-scale network resources because of a lack of reusability and scalability. This paper presents a matrix grammar approach for automatic distributed network resource management to alleviate these problems. A matrix grammar is proposed using WMI, CIM, and SNMP to manage network resources, and provides a generic mechanism to describe what needs to be managed and how to manage it. A scalable distributed multi-agent architecture for automatic network resource management is proposed, at its core lies a management automation engine consisting of a matrix analyzer and a recipe processor. The proposed solution has been implemented in software and applied in industrial products that achieve good technical and industrial results. It has good extensibility, scalability, and enables network management automation and software reusability.     

Parallel stereocorrelation on a reconfigurable multi-ring network

A reconfigurable network termed as the reconfigurable multi-ring network (RMRN) is described. The RMRN is shown to be a truly scalable network in that each node in the network has a fixed degree of connectivity and the reconfiguration mechanism ensures a network diameter of O(log₂ N) for anN-processor network. Algorithms for the two-dimensional mesh and the SIMD or SPMD n-cube are shown to map very elegantly onto the RMRN. Basic message passing and reconfiguration primitives for the SIMD/SPMD RMRN are designed for use as building blocks for more complex parallel algorithms. The RMRN is shown to be a viable architecture for image processing and computer vision problems using the parallel computation of the stereocorrelation imaging operation as an example. Stereocorrelation is one of the most computationally intensive imaging tasks. It is used as a visualization tool in many applications, including remote sensing, geographic information systems and robot vision.An earlier version of this paper was presented at the 1995 International Conference on Parallel and Distributed Processing Techniques and Applications.     

语义Web中开放知识服务体系的研究

WWW是信息时代的重要标志。基于WWW的信息管理系统不仅要能运行在不同的平台上、分布的信息网络中,而且还能提供通用的平台与大量的、独立的、多类型的数据源和应用程序进行交互。开放知识服务体系OKSA就是为实现这一目标而提出的,在开放的Web资源环境中,建立动态的、跨平台的虚拟知识环境,使得人们能够获取、发布、共享和管理各种Web资源,并向用户提供按需的知识服务以支持协同工作、问题求解和决策支持等。     

A class of highly scalable optical crossbar-connectedinterconnection networks (SOCNs) for parallel computing systems

A class of highly scalable interconnect topologies called the Scalable Optical Crossbar-Connected Interconnection Networks (SOCNs) is proposed. This proposed class of networks combines the use of tunable Vertical Cavity Surface Emitting Lasers (VCSEL's), Wavelength Division Multiplexing (WDM) and a scalable, hierarchical network architecture to implement large-scale optical crossbar based networks. A free-space and optical waveguide-based crossbar interconnect utilizing tunable VCSEL arrays is proposed for interconnecting processor elements within a local cluster. A similar WDM optical crossbar using optical fibers is proposed for implementing intercluster crossbar links. The combination of the two technologies produces large-scale optical fan-out switches that could be used to implement relatively low cost, large scale, high bandwidth, low latency, fully connected crossbar clusters supporting up to hundreds of processors. An extension of the crossbar network architecture is also proposed that implements a hybrid network architecture that is much more scalable. This could be used to connect thousands of processors in a multiprocessor configuration while maintaining a low latency and high bandwidth. Such an architecture could be very suitable for constructing relatively inexpensive, highly scalable, high bandwidth, and fault-tolerant interconnects for large-scale, massively parallel computer systems. This paper presents a thorough analysis of two example topologies, including a comparison of the two topologies to other popular networks. In addition, an overview of a proposed optical implementation and power budget is presented, along with analysis of proposed media access control protocols and corresponding optical implementation     

A virtual infrastructure for large-scale wireless sensor networks

The primary goal of a wireless sensor network is to collect useful information from the network. Most wireless sensor networks are assumed that the number of nodes are very large and they should operate with confined resources. Consequently it is important to take a scalable and energy-efficient architecture.In this paper, we present Railroad, a data collection and topology management architecture for large-scale wireless sensor networks. It proactively exploits a virtual infrastructure called Rail, which acts as a rendezvous area of the event data and queries. By using Rail, Railroad achieves scalability and energy efficiency under dynamic conditions with multiple mobile observers and targets. We evaluate the communication cost and the hot area message complexity of Railroad and compare them with previous approaches. We evaluate communication cost of Railroad by both an analytic model and simulations.     

Counting triangles in real-world networks using projections

Triangle counting is an important problem in graph mining. Two frequently used metrics in complex network analysis that require the count of triangles are the clustering coefficients and the transitivity ratio of the graph. Triangles have been used successfully in several real-world applications, such as detection of spamming activity, uncovering the hidden thematic structure of the web and link recommendation in online social networks. Furthermore, the count of triangles is a frequently used network statistic in exponential random graph models. However, counting the number of triangles in a graph is computationally expensive. In this paper, we propose the EigenTriangle and EigenTriangleLocal algorithms to estimate the number of triangles in a graph. The efficiency of our algorithms is based on the special spectral properties of real-world networks, which allow us to approximate accurately the number of triangles. We verify the efficacy of our method experimentally in almost 160 experiments using several Web Graphs, social, co-authorship, information, and Internet networks where we obtain significant speedups with respect to a straightforward triangle counting algorithm. Furthermore, we propose an algorithm based on Fast SVD which allows us to apply the core idea of the EigenTriangle algorithm on graphs which do not fit in the main memory. The main idea is a simple node-sampling process according to which node i is selected with probability \fracd_i2m{\frac{d_i}{2m}} where d _i is the degree of node i and m is the total number of edges in the graph. Our theoretical contributions also include a theorem that gives a closed formula for the number of triangles in Kronecker graphs, a model of networks which mimics several properties of real-world networks.     

Adversarial Queueing Model for Continuous Network Dynamics

In this paper we initiate the generalization of the Adversarial Queueing Theory (aqt) model to capture the dynamics of continuous scenarios in which the usually assumed synchronicity of the evolution is not required anymore. We propose an asynchronous model, named continuous aqt (caqt), in which packets can have arbitrary lengths, and the network links may have different speeds (or bandwidths) and propagation delays. With respect to the standard aqt model, these new features turn out to be significant for the stability of packet scheduling policies that take them into account, but not so much for the stability of networks. From the network point of view, we show that networks with directed acyclic topologies are universally stable, i.e., stable independently of the scheduling policies and traffic patterns used in it. Interestingly enough, this even holds for traffic patterns that make links to be fully loaded. Finally, it turns out that the set of universally stable networks remains the same as in the aqt model and, therefore, the property of universal stability of networks is decidable in polynomial time. Concerning packet scheduling policies, we show that the well-known lis, sis, ftgand nfsscheduling policies remain universally stable in the caqt model. We introduce other scheduling policies that, although being universally stable in the aqt model, they are unstable under the caqt model. This work was partially supported by eu IST-2004-15964 (aeolus), by the Spanish Ministry of Education and Science under cicyt tin2005-09198 (asce) and cicyt tin2005-25859-E, by the Regional Government of Madrid under contract No. 07T/0022/2003, and by the Universidad Rey Juan Carlos under project No. PPR-2004-42. Also partially supported by the Universidad de Chile (Mecesup fellowship and Anillo en Redes). A preliminary version of this work was presented in the 30th International Symposium on Mathematical Foundations of Computer Science (mfcs), Gdansk, Poland, LNCS, vol. 3618, pp. 144–155, Springer.     

Open Heterogeneous Computing in Actorspace

A number of efforts in heterogeneous computing involve the development of basic architecture independent communication primitives. We present a new programming paradigm, called ActorSpace, which provides a new communication model based on destination patterns. An actorspace is a computationally passive container of actors which acts as a context for matching patterns. Patterns are matched against listed attributes of actors and actorspaces that are visible in the actorspace. Both visibility and attributes are dynamic. Messages may be sent to one or all members of a group defined by a pattern. The paradigm provides powerful support for component-based construction of heterogeneous scalable distributed applications. In particular, it supports open interfaces to servers and pattern-directed access to software repositories.     

An integrated architecture for the provision of health telematic services based on digital library technologies

monolithic information system to effectively serve the needs of an entire healthcare organizational structure. Thus, information and telecommunications systems must primarily provide the infrastructure to support the effective integration of distributed and heterogeneous components, ensuring overall integrity in terms of functional and information interworking. This approach i.e., the integration of heterogeneous autonomous distributed systems, to developing and managing regional healthcare networks ensures the transfer and integration of consistent information between healthcare facilities, without imposing constraints on the operation of individual clinical units. This paper presents the results of an ongoing effort for the design and implementation of an architecture based on digital library technologies, for the provision of user-oriented telematic services in a regional healthcare network. Specifically, it addresses issues related to the provision of user-oriented services, transparent to the needs of different user groups and the requirements of specific tasks, based on: a) meta-information for the creation of an information infrastructure for the regional healthcare network which is, effectively, a multimedia distributed digital library, b) intelligent informationretrieval strategies to selectively retrieve information from multimedia data, c) agent-based technologies for effective service delivery adapted to the current user needs and the task at hand, and d) middleware services that explicitly reveal not only the characteristics of the information sources, but also address the context of specific telematic services, through appropriate mediation mechanisms. Received: 10 April 1997 / Revised: 6 July 1997 / Accepted: 5 August 1997     

An introduction to the multistage cube family of interconnection networks

The interconnection network in large-scale parallel/distributed supercomputer systems is a crucial component. Three networks are overviewed here. Multistage cube networks represent an important family of networks, which includes the omega, n-cube, multistage shuffle-exchange, delta, baseline, SW-banyan, and Generalized Cube. This family has been used or proposed for use in such systems as staran, pasm, Ultracomputer, the BBN Butterfly, the IBM RP3, and data-flow machines. The multistage cube topology, distributed routing control, and ability to be partitioned into independent subnetworks are examined. The Extra Stage Cube (ESC), a single-fault-tolerant multistage cube network, is described. The structure, control, and partitionability of the ESC, and how it functions when multiple faults occur, are presented. The Dynamic Redundancy (DR) network, a fault-tolerant multistage cube network that supports the incorporation of spare processors for fault tolerance, is discussed. Its structure, control, and partitionability into single-fault-tolerant subnetworks are explained.This research was supported by the Air Force Office of Scientific Research under grant F49620-86-K-0006, the Rome Air Development Center under grant F30602-83-K-0119, and the Purdue Research Foundation David Ross Grant 1985/86 no. 0857.currently with the Supercomputing Research Center, 4380 Forbes Blvd., Lanham, MD 20706 (as of June 1, 1987).currently with Computer Science Department, University of Illinois, Urbana-Champaign, IL 61801.     

新型路由器体系结构研究综述

计算机网络的管理与控制变得越来越复杂,人们对网络互连的关键设备--路由器提出了越来越高的要求。新型路由器控制体系结构必须考虑系统的开放性、可扩展性、可伸缩性、安全性、用户选择与应用感知等问题。本文分析了新型路由器控制体系结构的研究现状,重点介绍了主动网络、可编程网络、开放网络控制、软件可扩展路由器以及面向用户选择的网络控制等技术。     

A high-performance and scalable multi-core aware software solution for network monitoring

In recent years, the need for high-performance network monitoring tools, which can cope with rapidly increasing network bandwidth, has become vital. A possible solution is to utilize the processing power of multi-core processors that nowadays are available as commercial-off-the-shelf (COTS) hardware. In this paper, we introduce a software solution for wire-speed packet capturing and transmission for TCP/IP networks under Linux operating system, called DashCap. The results of our experimental evaluations show that the proposed solution causes more than two times performance boost for packet capturing in comparison to the existing software solutions under Linux. We have proposed a scalable software architecture for network monitoring tools called DashNMon, which is based on DashCap. Multi-core awareness is a distinguished property of this architecture. Comparing to the existing cluster-based solutions, DashNMon can be used with COTS multi-core processors. In order to evaluate the proposed solutions, we have developed several prototype tools. The results of the experiments carried out using these tools show the scalability and high performance of the network monitoring tools that are based on the proposed architecture. Using the proposed architecture, it is possible to design and implement high-performance multi-threaded network intrusion detection systems (NIDSs) or application-layer firewalls, completely in the user space and with better utilization of the computational resources of multi-processor/multi-core systems.     

From local neural networks to granular neural networks: A study in information granulation

In this study, we are concerned with a construction of granular neural networks (GNNs)—architectures formed as a direct result reconciliation of results produced by a collection of local neural networks constructed on a basis of individual data sets. Being cognizant of the diversity of the results produced by the collection of networks, we arrive at the concept of granular neural network, producing results in the form of information granules (rather than plain numeric entities) that become reflective of the diversity of the results generated by the contributing networks. The design of a granular neural network exploits the concept of justifiable granularity. Introduced is a performance index quantifying the quality of information granules generated by the granular neural network. This study is illustrated with the aid of machine learning data sets. The experimental results provide a detailed insight into the developed granular neural networks.     

Discovering timely information in MANETs

Timely information refers to information whose ‘most recent’ or ‘latest’ instance is most valuable. In mobile ad hoc networks (MANETs), multiple instances of a piece of timely information may be produced by different nodes at different points in time. The problem is to discover the ‘latest’ instance among all existing instances. Within the context of MANETs, timely information discovery is fundamentally different from the existing resource/service discovery problem whose goal is to discover either any instance or a subset of instances which satisfy a local query constraint that can be specified and evaluated using only local attributes of each individual node. In contrast, the timely information discovery problem imposes the global (timeliness) constraint which should best be evaluated when all the instances are considered to determine the latest instance. The complication of discovering timely information arises from the existence of multiple instances of the information, which are produced at different points in time by different nodes in the network, and the need to collect all these instances to decide the latest instance. For MANETs, the lack of infrastructure supports, frequent topology changes, and potential packet loss in wireless communications further challenge the problem of timely information discovery. This paper describes a self-organizing, peer-to-peer based approach, termed ALADIN, to discovering timely information in MANETs. In ALADIN, nodes that produce instances of the timely information are peers who self-organize an adaptive and distributed ‘search infrastructure’ to facilitate the discovery of the latest instance. A simulation study shows that ALADIN is scalable without incurring network-wide flooding in the case of large-scale networks and popular timely information, and yields a high chance of discovering the latest instance in the presence of mobility.