18435528
A review of fault management in WDM mesh networks: basic concepts and research challenges
The article first presents a broad overview of the fault management mechanisms involved in deploying a survivable optical mesh network which employs optical crossconnects. We review various protection and restoration schemes, primary and back-up route computation methods, shareability optimization, and dynamic restoration. We then describe different parameters that can measure the quality of service provided by a WDM mesh network to upper protocol layers (e.g., IP network backbones, ATM network backbones, leased lines, virtual private networks), such as service availability, service reliability, restoration time, and service restorability. We review these concepts, the factors that affect them, and how to improve them. In particular, we present a framework for cost-effective availability-aware connection provisioning to provide differentiated services in WDM mesh networks. Through the framework, the more realistic scenario of multiple near-simultaneous failures can be handled. In addition, the emerging problem of protecting low-speed connections of different bandwidth granularities is also reviewed.
11999738
The LLAMA Middleware Support for Accountable Service-Oriented Architecture
Enterprises are turning to SOA for the flexible deployment of business processes. While current monitoring tools can detect service execution problems in an enterprise's servers and report such problems to human decision makers, they may not closely monitor the external services they use, diagnose the root cause of process problems, and automatically reconfigure the process to replace faulty services. This paper presents the LLAMA middleware support for service process monitoring, run-time management, and configuration. Instances of accountability agents are deployed to selectively monitor some services' performance. These agents in turn allow LLAMA's Accountability Authority (AA) to diagnose process problems and apply any necessary reconfiguration. The project also builds tools to simplify the setup and deployment of LLAMA components. Our experimental results indicate that using LLAMA contributes only a modest amount of system overhead, and that the diagnosis process is swift and sufficiently accurate.
18359963
Backup reprovisioning to remedy the effect of multiple link failures in WDM mesh networks
As networks grow in size and complexity, both the probability and the impact of failures increase. The pre-allocated backup bandwidth, which has been widely investigated in the literature, may not be able to provide full protection guarantee when multiple failures occur in a network. In this study, we consider multiple concurrent failures where concurrent means that a new failure occurs before a previous failure is repaired. To combat the effect of multiple concurrent failures, new backups can be reprovisioned after one failure such that the next potential failure can be handled effectively and efficiently. We consider dynamic traffic where a pair of link-disjoint primary and backup paths is provisioned when a new connection request arrives. After a failure occurs, the affected connections switch traffic from their primary paths to backup paths. To protect against next potential failure, we reprovision new backups for connections that become unprotected or vulnerable because of losing their primary or their backup due to the previous failure or due to backup resource sharing. This approach is called Minimal Backup Reprovisioning (MBR). An alternative approach is to globally rearrange backups for all connections after one failure occurs, which is called Global Backup Reprovisioning (GBR). Backup reprovisioning can be performed whenever the network's state changes, e.g., (1) when a new request arrives, (2) when an existing connection terminates, (3) when a network failure occurs, (4) when a failed link/node is repaired, etc., to utilize the available resources more efficiently or to recover quickly from the next failure. In this study, we perform MBR or GBR after one network failure occurs to protect against the next potential failure in a wavelength-convertible WDM mesh network. The link-vector network model which can maximally explore the backup-sharing potential is assumed in this study. We then analyze the complexity of MBR and GBR under such a network model. A reprovisioning algorithm is proposed for MBR which can significantly reduce the connection vulnerability without the knowledge of the location of the next failure. In GBR, both integer linear program (ILP) and heuristic-based approaches are proposed. We compare capacity requirement and computational complexity of MBR to that of GBR through numerical examples. MBR demonstrates a good tradeoff between complexity and capacity efficiency to handle multiple concurrent failures
31253731
Explicit Routing for Traffic Engineering in Labeled Optical Burst-Switched WDM Networks
Optical burst switching (OBS) is a promising technique for supporting high-capacity bursty data traffic over optical wavelength-division-multiplexed (WDM) networks. A label-switched path can be established to forward a burst control packet (BCP) if each OBS node is augmented with an IP/MPLS controller. Such a network is called a labeled OBS (LOBS) network, and it can exploit the explicit routing and constraint-based routing properties supported in the MPLS framework to perform traffic and resource engineering. In this paper, we consider the traffic-engineering problem in a LOBS network, using explicit routing to balance network load and to reduce the burst-loss probability. We model the traffic-engineering problem in a LOBS network as an optimization problem and propose two new objective functions to minimize network congestion. Our illustrative numerical examples show that the burst-loss probability can be significantly reduced using optimization technique, when compared with shortest-path routing.
18478421
An Efficient Approach for Service Process Reconfiguration in SOA with End-to-End QoS Constraints
Using SOA, service processes can be composed statically or dynamically using services provided by different service providers. Some services may become faulty at runtime and cause the service process to violate the end-to-end quality of service (QoS) constraint. We propose an efficient approach for replacing faulty services to ensure that the reconfigured service process still meets the original end-to-end QoS constraint. We use an iterative algorithm to identify reconfiguration regions that have a small number of services, some faulty and some healthy, in order to have more service selection options. By reconfiguring services in these selected regions rather than the whole service process, the computational complexity is significantly reduced. Simulation study has shown that our approach is efficient as most service processes can be repaired by replacing only a small number of services.
495478
Optimized routing for fault management in optical burst-switched WDM networks
Optical burst switching (OBS) is a promising technique for supporting high-capacity, bursty data traffic over optical wavelength-division-multiplexed (WDM) networks. An optical link failure may result in a huge amount of data (and revenue) loss, and it has been an important survivability concern in optical networks. In this paper, we study the fault- management issues related with a link failure in an OBS network. We propose to use pre-planned global rerouting to balance network load and to reroute bursts after a link fails. We apply optimization techniques to pre-plan explicit backup routes for failure scenarios. Our objective is to achieve optimal load balancing both before and after a failure such that the network state can still remain stable with minimum burst-loss probability when a failure occurs. We apply the pre-planned normal and backup routing tables to an OBS network, and study the network performance after a failure occur using illustrative numerical examples. The results show that the average burst-loss probability can be significantly reduced by 60% - from an average of 0.10 to 0.04 (when the normalized link load is less than 0.5) using globally-rerouted backup routes, when compared with the scheme without global rerouting. We also observe that the burst-loss probability is reduced by 43% - from an average of 0.07 to 0.04 (when the link load is less than 0.5) if the rerouting is done using optimization techniques, when compared with shortest-path routing.for Fault Management
62240401
A model-based approach to adding autonomic capabilities to network fault management system
Adding autonomic capabilities to network management systems provides great promise in delivering high QoS while lowering operation and maintenance cost. In this paper, we present a model-based approach to adding autonomic capabilities to a fault management system for cellular networks. We propose the use of modeling techniques to specify software failures and their dispositions at the model level for the target system. This facilitates the deployment of a control loop for adding autonomic capabilities into the system architecture, which include self-monitoring, self-healing, and self-adjusting. Our case study on the intelligent network fault management system illustrates the proposed approach by adding and deploying these autonomic capabilities derived from self-model specifications, to mitigate the risk of specified failures and maintain the level of healthiness of the system, dynamically and effectively.
4805412
Notice of RetractionEffect of Gaze Direction and Face Expression on Visual Reflexive Attention
As important social clues, gaze direction and expression usually influence people's social interaction in their communication, and facial cognition is also a hot topic in social cognitive study. In our studies, by comparing facial cognition in upright and inverted face, considering both gaze direction and expression, we tried to explore the mechanism of gaze and expression processing by the method of Posner, and explored sex difference in it. Results indicated that gaze direction could act as a central cue and brought out benefit effect and cost effect only when face is upright. While negative expression would act as an abstractor and prolonged the reflexive attention to target also only in upright face, which means expression and gaze direction were both processed by holistic with the face. What's more, we found sex difference in these two processing.
1181158
Weaving Deployment Aspects into Domain-specific Models
Domain-specific models increase the level of abstraction used to develop large-scale component-based systems. Model-driven development (MDD) approaches (e.g., Model-Integrated Computing and Model-Driven Architecture) emphasize the use of models at all stages of system development. Decomposing problems using MDD approaches may result in a separation of the artifacts in a way that impedes comprehension. For example, a single concern (such as deployment of a distributed system) may crosscut different orthogonal activities (such as component specification, interaction, packaging and planning). To keep track of all entities associated with a component, and to ensure that the constraints for the system as a whole are not violated, a purely model-driven approach imposes extra effort, thereby negating some of the benefits of MDD. This paper provides three contributions to the study of applying aspect-oriented techniques to address the crosscutting challenges of model-driven component-based distributed systems development. First, we identify the sources of crosscutting concerns that typically arise in model-driven development of component-based systems. Second, we describe how aspect-oriented model weaving helps modularize these crosscutting concerns using model transformations. Third, we describe how we have applied model weaving using a tool called the Constraint-Specification Aspect Weaver (C-SAW) in the context of the Platform-Independent Component Modeling Language (PICML), which is a domain-specific modeling language for developing component-based systems. A case study of a joint-emergency response system is presented to express the challenges in modeling a typical distributed system. Our experience shows that model weaving is an effective and scalable technique for dealing with crosscutting aspects of component-based systems development.
2730805
Applying PageRank Algorithm in Requirement Concern Impact Analysis
As an important part of requirement management, managing requirement change plays a key role in controlling project schedule and costs at early stage. Effective requirement impact analysis would give proper assessment on the effect of certain requirement changes on the whole system, and provide useful information for making trade-off decisions on future system design and implementation. In this paper a quantitative approach to concern impact analysis at requirement level has been proposed with the application of PageRank algorithm, which is a successful link based web page sorting algorithm. At first, separation of concerns is applied during deriving formal requirement specification from textual requirement statements. Next, concerns are specified and concern relationship graph is established. Finally, PageRank algorithm is utilized on concern relationship graph for assessing the impact of concern changes. Our approach has been applied to hallway section in Light Control System and validation of analysis result has been stated.
30018886
Federation Based Solution for Peer-to-Peer Network Management
Recently, Peer-to-Peer (P2P) technology has become one of the hottest topics in the research area of Internet. With a variety of P2P applications, especially those applications sharing large-size file resources among a large scale of user community, P2P brought us an even more exciting Internet life. However, P2P also made lots of troubles to network managers because of consuming too much network bandwidth sometimes. Lacking of effective management solution, some ISPs plan to block all P2P services on their network boundaries. In this paper, we propose a federation-based solution for peer-to-peer network management. By setting up a P2P federation, ISPs and P2P service providers can work together for P2P network management. From P2P federation service, ISPs can get P2P nodes information of their own network to make some control to those that disturb normal network services. At the same time, service providers of P2P may get routing information of specific ISPs to optimize the routing of P2P network itself by joining in federation. Under such scenario, it will save much cost for ISPs to detect and control P2P traffic and give up the idea of killing P2P services. Save and help to the development of P2P are the most important target of this solution.