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In a distributed computing environment, guaranteeing the hard deadline for real-time messages is essential to ensure schedulability of real-time tasks. Since capabilities of the shared resources for transmission are limited, e.g., the... more
In a distributed computing environment, guaranteeing the hard deadline for real-time messages is essential to ensure schedulability of real-time tasks. Since capabilities of the shared resources for transmission are limited, e.g., the buffer size is limited on network devices, it becomes a challenge to design an effective and feasible resource sharing policy based on both the demand of real-time packet transmissions and the limitation of resource capabilities. We address this challenge in two cooperative mechanisms. First, we design a static routing algorithm to find forwarding paths for packets to guarantee their hard deadlines. The routing algorithm employs a validation-based backtracking procedure capable of deriving the demand of a set of real-time packets on each shared network device, and it checks whether this demand can be met on the device. Second, we design a packet scheduler that runs on network devices to transmit messages according to our routing requirements. We implem...
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Pervasive virtualization at the edge and in the network core drives the evolution of the IT infrastructure towards a service-oriented model [1]. It permits a move from static arrangements of resources that persist over long periods of
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This paper describes advanced capabilities that were deployed recently in the ExoGENI testbed to offer increased flexibility in provisioning, modifying, and recovering the topologies and the configuration settings of the virtual systems,... more
This paper describes advanced capabilities that were deployed recently in the ExoGENI testbed to offer increased flexibility in provisioning, modifying, and recovering the topologies and the configuration settings of the virtual systems, or slices, in which experiments are run. Using the analogy of building complex structures with LEGO blocks, we envision an environment in which users arbitrarily scale out, scale in, scale up, and scale down their topologies using various modular constructs of compute, storage, and network resources. Portions of topologies can be shut down and brought back up to support resiliency, repeatability, migration, and other needs of the control software or application. Distributed applications running inside of slices can require programmatic control over the evolution of the topology as the execution progresses. The introduced capabilities, slice modification and slice recovery, are used either with the user GUI or through the programmable APIs. These new...
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Path querying on Semantic Networks is gaining increased focus because of its broad applicability. Some graph databases offer support for variants of path queries e.g. shortest path. However, many applications have the need for the set... more
Path querying on Semantic Networks is gaining increased focus because of its broad applicability. Some graph databases offer support for variants of path queries e.g. shortest path. However, many applications have the need for the set version of various path problem i.e. finding paths between multiple source and multiple destination nodes (subject to different kinds of constraints). Further, the sets of source and destination nodes may be described declaratively as patterns, rather than given explicitly. Such queries lead to the requirement of integrating graph pattern matching with path problem solving. There are currently existing limitations in support of such queries (either inability to express some classes, incomplete results, inability to complete query evaluation unless graph patterns are extremely selective, etc).
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In a distributed computing environment, guaranteeing the hard deadline for real-time messages is essential to ensure schedulability of real-time tasks. Since capabilities of the shared resources for transmission are limited, e.g., the... more
In a distributed computing environment, guaranteeing the hard deadline for real-time messages is essential to ensure schedulability of real-time tasks. Since capabilities of the shared resources for transmission are limited, e.g., the buffer size is limited on network devices, it becomes a challenge to design an effective and feasible resource sharing policy based on both the demand of real-time packet transmissions and the limitation of resource capabilities. We address this challenge in two cooperative mechanisms. First, we design a static routing algorithm to find forwarding paths for packets to guarantee their hard deadlines. The routing algorithm employs a validation-based backtracking procedure capable of deriving the demand of a set of real-time packets on each shared network device, and it checks whether this demand can be met on the device. Second, we design a packet scheduler that runs on network devices to transmit messages according to our routing requirements. We implem...
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To support the scalability and resilience requirements of distributed Wide-Area Measurement System (WAMS) architectures, we design and implement a software infrastructure to estimate power grid oscillation modes based on real-time data... more
To support the scalability and resilience requirements of distributed Wide-Area Measurement System (WAMS) architectures, we design and implement a software infrastructure to estimate power grid oscillation modes based on real-time data collected from Phasor Measurement Units (PMUs). This estimation algorithm can be deployed on a hierarchical structure of Phasor Data Concentrators (PDCs), which calculate local estimates and communicate with each other to calculate the global estimate. This work contributes a resilient system to WAMS with guarantees for (1) Quality of Service in network delay, (2) network failure tolerance, and (3) self-recoverability. The core component of the infrastructure is a distributed storage system. Externally, the storage system provides a cloud data lookup service with bounded response times and resilience, which decouples the data communication between PMUs, PDCs, and power-grid monitor/control applications. Internally, the storage system organizes PDCs as...
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In this paper we describe an advanced hardwarein-loop simulation facility for real-time demonstration and validation of power system monitoring and control algorithms, recently constructed at NC State University. This facility integrates... more
In this paper we describe an advanced hardwarein-loop simulation facility for real-time demonstration and validation of power system monitoring and control algorithms, recently constructed at NC State University. This facility integrates a real-time power system emulation lab with the GENI network and its associated cloud testbeds. The dynamic responses from the power system emulator are captured via real hardware Phasor Measurement Units (PMU) that are synchronized with the time-scale of the simulations via a common GPS reference. These responses are then sent to the computing and storage resource in GENI using the IEEE C37.118 protocol, running the smart grid control and management application simulations via QoS-guaranteed communications channels, all provisioned in a dynamic fashion. The facility is currently being used for real-time oscillation monitoring of large prototype power system models executed over a distributed EXO-GENI communication network.
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Research Interests: Computer Science, Architecture, Distributed System, Computer Network, Communication Network, and 10 moreRing, Metropolitan Area Network, Network Architecture, Optical telecommunication, Wavelength, Wavelength Division Multiplexing, Subnetwork Analysis, Reconfiguration, Control Reconfiguration, and Metropolitan Area
In this paper we address the problem of implementing wide-area oscillation monitoring algorithms for large power system networks using distributed processing of Synchrophasor measurements. We consider two computational approaches, namely... more
In this paper we address the problem of implementing wide-area oscillation monitoring algorithms for large power system networks using distributed processing of Synchrophasor measurements. We consider two computational approaches, namely decentralized least squares (DLS) and its recursive implementation (RLS). Both algorithms are executed using multiple phasor data concentrators (PDC), deployed as virtual computing machines communicating over a fiber-optic communication network. Results are demonstrated using the US-Wide ExoGENI communication network connected to a PMU test bed at NC State University, and analyze the end-to-end computational and communication delays for both algorithms.
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This chapter continues the discussion of expanding Grid networking capabilities through flexible and efficient utilization of network resources. Specifically, it focuses on the important topic of integrating Grid environments directly... more
This chapter continues the discussion of expanding Grid networking capabilities through flexible and efficient utilization of network resources. Specifically, it focuses on the important topic of integrating Grid environments directly with layer 1 optical network services. Included in ...
Research Interests: Computer Science and Grid
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We consider the problem of designing an MPS network of optical cross-connects (OXCs) to interconnect a given number of label switched routers (LSRs). We present a set of heuristic algorithms to address the combined problem of physical... more
We consider the problem of designing an MPS network of optical cross-connects (OXCs) to interconnect a given number of label switched routers (LSRs). We present a set of heuristic algorithms to address the combined problem of physical topology design (ie, determine the number of OXCs required and the ber links among them) and logical topology design (ie, determine the routing and wavelength assignment for the lightpaths among the LSRs). Unlike previous studies which were limited to small topologies with a handful of ...
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We consider the problem of designing a network of optical cross-connects (OXCs) to provide end-to-end lightpath services to large numbers of label switched routers (LSRs). We present a set of heuristic algorithms to address the combined... more
We consider the problem of designing a network of optical cross-connects (OXCs) to provide end-to-end lightpath services to large numbers of label switched routers (LSRs). We present a set of heuristic algorithms to address the combined problem of physical topology design and logical topology design. Unlike previous studies which were limited to small topologies, we have applied our algorithms to networks with hundreds or thousands of LSRs and with a number of lightpaths that is an order of magnitude larger ...
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Research Interests: Engineering, Computer Science, Medical Imaging, Fiber Optics, Genetic Algorithms, and 15 moreGenetic Algorithm, Numerical Simulation, Computer Network, Light, Cost effectiveness, Nodes, Computational Efficiency, Heuristic, Network Topology, Lower Bound, Logic Design, Large Scale, Internet, Electrical And Electronic Engineering, and Heuristic algorithm
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Research Interests: Optics, Medical Imaging, Fiber Optics, Telecommunications, Genetic Algorithms, and 24 moreRouting, Resource Allocation, Photonics, Routing protocols, Genetic Algorithm, Numerical Simulation, Society, Optical, Light, Cost effectiveness, Nodes, Computational Efficiency, Optical network, Optical physics, Wavelength Division Multiplexing, Network Topology, Lower Bound, Logic Design, Large Scale, Internet, Electrical And Electronic Engineering, Optical Cross-connect, Heuristic algorithm, and Transceivers
We consider the problem of designing a network of optical cross-connects (OXCs) to provide end-to-end lightpath services to large numbers of label switched routers (LSRs). We present a set of heuristic algorithms to address the combined... more
We consider the problem of designing a network of optical cross-connects (OXCs) to provide end-to-end lightpath services to large numbers of label switched routers (LSRs). We present a set of heuristic algorithms to address the combined problem of physical topology design and logical topology design. Unlike previous studies which were limited to small topologies, we have applied our algorithms to networks with hundreds or thousands of LSRs and with a number of lightpaths that is an order of magnitude larger ...
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ABSTRACT Traditionally data management software running on top of the Internet has very limited primitives to interact with the networking layer. This limitation has become a major road-block to develop next generation data management... more
ABSTRACT Traditionally data management software running on top of the Internet has very limited primitives to interact with the networking layer. This limitation has become a major road-block to develop next generation data management applications requiring high-bandwidth and dynamic network configuration. In this work, we present a policy-driven software framework that acts as an adaptation layer between the data management software and SDN networks. This framework allows a tight coupling between the data grid and the network and therefore makes complex workflow-like cross-layer computation possible. We have prototyped this adaptation layer integrated with iRODS, a popular policy-driven data grid software and Floodlight, a popular OpenFlow controller, and demonstrate how network policies become part of the overall data grid policies to improve the application performance.
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ABSTRACT Future wide-area measurement and control applications in large electric power systems will require a new decentralized architecture that scales up with the rapidly growing deployment of Phasor Measurement Units (PMUs). The... more
ABSTRACT Future wide-area measurement and control applications in large electric power systems will require a new decentralized architecture that scales up with the rapidly growing deployment of Phasor Measurement Units (PMUs). The emerging cloud computing paradigm that allows dynamic creation of virtual machines to form virtual data centers would help better support this new architecture through more efficient and flexible use of the networking and computing resources. However, this paradigm shift poses new technical challenges to the underneath communication and computing infrastructure leading to new problem formulations and solution approaches. Given that the primary communication pattern in the decentralized system will consist of various types of real-time group communication methods, in this paper we present a preliminary study on two problems, namely communication group formation and routing, that are fundamental to the envisioned new communication architecture.
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ABSTRACT
This paper presents a cost-effective virtual topology design framework based on virtual rings in both ring and mesh optical WDM networks. The traffic grooming problem is solved in separate steps, in which different objectives are... more
This paper presents a cost-effective virtual topology design framework based on virtual rings in both ring and mesh optical WDM networks. The traffic grooming problem is solved in separate steps, in which different objectives are considered. The nodes are first grouped into clusters, each cluster forms a ring with the self healing property, then hub nodes are decided such that
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ABSTRACT In this poster we describe an advanced hardware-in-loop simulation facility for real-time demonstration and validation of power system monitoring and control algorithms, currently under construction at NC State University. This... more
ABSTRACT In this poster we describe an advanced hardware-in-loop simulation facility for real-time demonstration and validation of power system monitoring and control algorithms, currently under construction at NC State University. This facility integrates a real-time power system emulation lab with the GENI network and its associated cloud testbeds. The dynamic responses from the power system emulator are captured via real hardware Phasor Measurement Units (PMU) that are synchronized with the time-scale of the simulations via a common GPS reference. These responses are then sent to the computing and storage resource in GENI using the IEEE C37.118 protocol, running the smart grid control and management application simulations via QoS-guaranteed communications channels, all provisioned in a dynamic fashion.
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ABSTRACT The fault diagnosis method using a signed directed graph (SDG) based on qualitative model as a model of the system is useful to real-time diagnosis of failures that occur in process. First, it establishes the SDG of the systems... more
ABSTRACT The fault diagnosis method using a signed directed graph (SDG) based on qualitative model as a model of the system is useful to real-time diagnosis of failures that occur in process. First, it establishes the SDG of the systems and components, simplifies these SDG corresponding to the fault modes needing to be diagnosed, at the same time SDG are described the many rules forms for shortening the calculating time of making use of SDG, then expands the diagnosing rule with expert knowledge to construct the diagnosing rule bank of the system. Second, the fault modes can be primary diagnosed by using the constructed rules. And then the modes that can not be distinguished are diagnosed by adding adequate quantitative information. The case studies show that the problem of misoperation autodiagnosis during computer simulation training can be solved effectively, and the SDG diagnosis method has good completeness, fine resolution and detailed explanation in actual industrial process.
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The backbone of IT infrastructure is evolving towards a service-oriented model, in which distributed resources, ei- ther software or hardware, can be composed as a customized IT service on demand. In particular, cloud computing... more
The backbone of IT infrastructure is evolving towards a service-oriented model, in which distributed resources, ei- ther software or hardware, can be composed as a customized IT service on demand. In particular, cloud computing infrastructure services manage a shared "cloud" of servers as a unified hosting substrate for diverse applications, using various technologies to virtualize servers and orche strate their operation. Emerging cloud infrastructure-as - a-service efforts include Eucalyptus, Nimbus, Tashi, OpenCirrus, and IBM's Blue Cloud. Extending cloud hosting into the network is a crucial step to enable on-demand allocation of complete net- worked IT environments. This paper reports on our effort to advance cloud resource control to cloud networks with multiple substrate providers, including network tran sit providers. Our vision is to enable cloud applica- tions to request virtual servers at multiple points in the ne twork, together with bandwidth-provisioned n...
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The majority of previous OBS network performance studies has focused on solutions to reduce the channel blocking (when there is no available wavelengths on some link(s) or switch output ports along the burst route for a burst) while... more
The majority of previous OBS network performance studies has focused on solutions to reduce the channel blocking (when there is no available wavelengths on some link(s) or switch output ports along the burst route for a burst) while ignoring the receiver blocking (when the receiver at a destination is serving another bursts when a burst arrives) with the assumption of unlimited number of receivers per destination. Xu et al. presented a simulation study on the receiver blocking for an OBS ring of special structure under different scheduling schemes. 1 In this paper, we propose to use multiple receivers or a FDL at the destination node to reduce the receiver blocking for a general bidirectional OBS ring with transmitter and receiver that both are fast tunable. Assuming Poisson burst arrival, exponential burst duration and receiver tuning time, and K receivers, a destination node can be modeled as an M/M/K/K queue. The receiver blocking probability p r follows the Erlang's loss for...
A backbone-based hybrid network architecture has the potential to enhance the connectivity and throughput capacity of wireless ad-hoc networks. A fundamental problem for this hybrid network archi-tecture is designing the optimal network... more
A backbone-based hybrid network architecture has the potential to enhance the connectivity and throughput capacity of wireless ad-hoc networks. A fundamental problem for this hybrid network archi-tecture is designing the optimal network topology un-der certain topological constraints. In this paper, this problem is formulated as a generalized optimal geo-metric Steiner network problem with minimum num-ber of Steiner nodes under the various practical con-straints. In this new problem formulation, the back-bone (Steiner) nodes have two heterogeneous trans-mission ranges, one for connecting to the terminal nodes and the other for connecting to other backbone nodes. The overall network and the backbone subnet-work are both connected. We also consider the case when the number of hops from a terminal node to its closest backbone node is constrained. As the prob-lem is NP-hard, we propose a multiple-step solution approach, compare several heuristic algorithms by a comprehensive simulation ...
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This paper reports on experience with using semantically-enabled network resource models to construct an operational multi-domain networked infrastructure-as-a-service (NIaaS) testbed called ExoGENI, recently funded through NSF's GENI... more
This paper reports on experience with using semantically-enabled network resource models to construct an operational multi-domain networked infrastructure-as-a-service (NIaaS) testbed called ExoGENI, recently funded through NSF's GENI project. A defining property of NIaaS is the deep integration of network provisioning functions alongside the more common storage and computation provisioning functions. Resource provider topologies and user requests can be described using network resource models with common base classes for fundamental cyber-resources (links, nodes, interfaces) specialized via virtualization and adaptations between networking layers to specific technologies. This problem space gives rise to a number of application areas where semantic web technologies become highly useful - common information models and resource class hierarchies simplify resource descriptions from multiple providers, pathfinding and topology embedding algorithms rely on query abstractions as buil...
ABSTRACT Due to the economy of scale of Ethernet networks and available dynamic circuit capability from the major national research and educational networks, VLAN (Virtual LAN) based virtual networking solution has been successfully... more
ABSTRACT Due to the economy of scale of Ethernet networks and available dynamic circuit capability from the major national research and educational networks, VLAN (Virtual LAN) based virtual networking solution has been successfully adopted in some advanced distributed cloud systems. However, there are two major constraints in this adaptation: (1) dynamic circuit service is far from pervasive; (2) there is only limited VLAN tags offered by regional network service providers. In this paper, after examining layer-2 networking in large-scale distributed cloud environments, we present a graph theoretical model to study the network capacity in terms of the number of inter-cloud connections that can co-exist. We further design the algorithms to achieve this capacity for both point-to-point and multi-point inter-cloud connections in both static and dynamic scenarios. We also study a general topology embedding problem based on this model. As tagging is a common mechanism for isolating communication channels in other network layers, the proposed models and algorithms can be extended to optical and IP networks.
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ABSTRACT It is essential for distributed, data-intensive applications to monitor the performance of the underlying network, storage, and computational resources. Increasingly, distributed applications need performance information from... more
ABSTRACT It is essential for distributed, data-intensive applications to monitor the performance of the underlying network, storage, and computational resources. Increasingly, distributed applications need performance information from multiple aggregates, and tools need to make real-time steering decisions based on the performance feedback. With increasing scale and complexity, the volume and velocity of monitoring data is increasing, posing scalability challenges. In this work, we have developed a persistent query agent (PQA) that provides real-time application and network performance feedback to clients/ applications, thereby enabling dynamic adaptations. The PQA enables federated performance monitoring by interacting with multiple aggregates and performance monitoring sources. Using a publish-subscribe framework, it sends triggers asynchronously to applications/clients when relevant performance events occur. The applications/clients register their events of interest using declarative queries and get notified by the PQA. The PQA leverages a complex event processing (CEP) framework for managing and executing the queries expressed in a standard SQL-like query language. Instead of saving all monitoring data for future analysis, PQA observes performance event streams in real time, and runs continuous queries over streams of monitoring events. In this work, we present the design and architecture of the PQA, and describe some relevant use cases.