25656460
Dynamic provisioning with availability guarantee for differentiated services in survivable mesh networks
Survivability is a key concern in modern network design in order to achieve fast service restorability against network failures. This paper investigates the problem of survivable dynamic connection provisioning in general telecom backbone networks, which are mesh structured. These networks employ optical fibers, which may fail due to network outages such as fiber cuts, etc. Our study applies to survivability of optical wavelength-division multiplexing (WDM) as well as multi-protocol label switching (MPLS) networks. For survivability study, we assume differentiated services where connections may have different availability requirements, so they may be provisioned differently with protection (if needed) based on their availability requirements and current network state. Therefore, it may be possible that connections with the same source, destination, and availability requirement are provisioned differently (unprotected, shared-path protected, or dedicated-path protected) at different times based on current network state. Such differentiated provisioning can provide diverse levels of service performance and achieve network resource optimization flexibly. Our main contributions are as follows. First, we develop an analytical model to quantify the availabilities of connections with various protection modes, i.e., unprotected, dedicated-path protected, and shared-path protected. Particular emphasis is placed on computing a connection's availability with shared-path protection by employing the link-vector technique, because this technique can maximally explore the sharing potential among backup paths and achieve bandwidth-assignment flexibility. Based on the mathematical model, we then present a novel provisioning strategy for dynamic connection requests in which multiple levels of services are provided and different protection schemes may be applied to different connections. The strategy jointly considers both connection availability satisfaction and resource optimization. Numerical results show very good accuracy of our model and high effectiveness of our provisioning strategy
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.
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
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
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.
33955645
A Dynamic Scalable Video Conference System Based on SIP
The Session Initiation Protocol (SIP) provides powerful and flexible signaling capabilities for building video conferencing services. Traditionally, for SIP-based centralized video conference systems, the conferencing scale is mainly limited by both the capability of conference server and the availability of bandwidth. In this paper, our design focuses on how to provide dynamic scalability for the SIP-based video conferencing system when the number of conference users increases continually. Based on the study of the SIP protocol and the existing video conferencing models, we propose a dynamic scalable service model that can support to dynamically increase the number of conference servers without negative influence on the stability of system. This enables the extra service requests to be transferred and served in the cooperated conference servers. The paper also addresses the SIP-enabled conferencing flows based on the model in detail. We developed a prototype of video conference system based on the proposed model. Experimental results demonstrate the validity of this service model.
16103716
Numerical Simulation of Fluid Flow in Thin Slab Continuous Casting Mould
According to actual circumstance of Han Iron and Steel Company CSP, a three-dimensional mathematical model of fluid flow in the mould has been developed. The process of fluid flow is simulated in aid of fluid simulation software FLUENT, when we use two kinds of SEN separately in cast. The fluid flow in the mould is simulated at the difference of technical parameters (flow-guiding slot angle and submerge depth), when using two kind of SEN separately. And the optimum SEN configuration (flow-guiding slot angle) and submerge depth are fixed based on the numerical simulation.
2702943
Specifying real-time properties in autonomic systems
Increasingly, computer software must adapt dynamically to changing conditions. The correctness of adaptation cannot be rigorously addressed without precisely specifying the requirements for adaptation. In many situations, these requirements involve absolute time, in addition to a logical ordering of events. This paper introduces an approach to formally specifying such timing requirements for adaptive software. We introduce TA-LTL, a timed adaptation-based extension to linear temporal logic, and use this logic to specify three timing properties associated with the adaptation process: safety, liveness, and stability. A dynamic adaptation scenario involving interactive audio streaming software is used to illustrate the timed temporal logic.
606471
A dynamic scalable service model for SIP-based video conference
As an extensible signaling protocol, SIP (session initiation protocol) can be applied in developing video conference system. Traditionally, for SIP-based centralized video conference system, conferencing scale is limited by both the capability of conference server and the availability of bandwidth. The paper focuses on how to keep conferencing when the number of conference users increases. Based on the study of the SIP protocol, we analyze the drawback of the existing video conference model, and propose a dynamic scalable service model for SIP-based video conference. By this model, the extra service requests can be transferred and served in the cooperated conference servers. The paper presents the conferencing control policy of the model in detail. We developed a prototype of video conference system based on the above model. Experimental results show this service model works well.
8627694
Interweave Neural Networks with Evolutionary Algorithms, Cellular Computing, Bayesian Learning and Ensemble Learning
A neural networks are able to give solutions to complex problems in business intelligence and financial engineering due to their nonlinear processing. This paper consists of a survey of various business intelligence and financial engineering and so on applications based on the neural networks, and also a summary of the recent techniques such as still evolutionary algorithms, cellular computing, Bayesian learning and ensemble learning. The neural networks can be powerful tools in several fields of business intelligence and financial engineering. It can be concluded that, the future of neural networks lies in their use in conjunction with other advanced technologies.