233 research outputs found

    Ant-based Survivable Routing in Dynamic WDM Networks with Shared Backup Paths

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    Protection and restoration algorithms for WDM optical networks

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    Currently, Wavelength Division Multiplexing (WDM) optical networks play a major role in supporting the outbreak in demand for high bandwidth networks driven by the Internet. It can be a catastrophe to millions of users if a single optical fiber is somehow cut off from the network, and there is no protection in the design of the logical topology for a restorative mechanism. Many protection and restoration algorithms are needed to prevent, reroute, and/or reconfigure the network from damages in such a situation. In the past few years, many works dealing with these issues have been reported. Those algorithms can be implemented in many ways with several different objective functions such as a minimization of protection path lengths, a minimization of restoration times, a maximization of restored bandwidths, etc. This thesis investigates, analyzes and compares the algorithms that are mainly aimed to guarantee or maximize the amount of remaining bandwidth still working over a damaged network. The parameters considered in this thesis are the routing computation and implementation mechanism, routing characteristics, recovering computation timing, network capacity assignment, and implementing layer. Performance analysis in terms of the restoration efficiency, the hop length, the percentage of bandwidth guaranteed, the network capacity utilization, and the blocking probability is conducted and evaluated

    Priority based dynamic lightpath allocation in WDM networks.

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    Internet development generates new bandwidth requirement every day. Optical networks employing WDM (wavelength division multiplexing) technology can provide high capacity, low error rate and low delay. They are considered to be future backbone networks. Since WDM networks usually operate in a high speed, network failure (such as fiber cut), even for a short term, can cause huge data lost. So design robust WDM network to survive faults is a crucial issue in WDM networks. This thesis introduces a new and efficient MILP (Mixed Integer Linear Programming) formulation to solve dynamic lightpath allocation problem in survivable WDM networks, using both shared and dedicated path protection. The formulation defines multiple levels of service to further improve resource utilization. Dijkstra\u27s shortest path algorithm is used to pre-compute up to 3 alternative routes between any node pair, so as to limit the lightpath routing problem within up to 3 routes instead of whole network-wide. This way can shorten the solution time of MILP formulation; make it acceptable for practical size network. Extensive experiments carried out on a number of networks show this new MILP formulation can improve performance and is feasible for real-life network. Source: Masters Abstracts International, Volume: 43-01, page: 0249. Adviser: Arunita Jaekel. Thesis (M.Sc.)--University of Windsor (Canada), 2004

    Efficient Protection of Many-to-One Communications

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    International audienceThe dependability of a network is its ability to cope with failures , i.e., to maintain established connections even in case of failures. IP routing protocols (such as OSPF and RIP) do not fit the dependability objectives of today applications. Moreover, forwarding techniques based on destination address (like IP) induce many-to-one connections. If a dependable connection is needed, all primary paths and protections having the same destination must be established in a coordinated way. In this paper, we propose a fault recovery for many-to-one connections based on a cold (preplanned) protection. The main advantage of our approach is that the recovery in case of failures is achieved within a short delay. Additionally, with respect to other approaches, the dependability of the routing scheme is increased in the way that it statistically copes with many failures. The algorithm we propose computes an efficient backup for an arbitrary primary tree using an improved multi-tree algorithm

    Efficient path protection using Bi-directional WDM transmission technology

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    Bi-directional WDM transmission is a technique that allows wavelengths to be transmitted simultaneously in both directions in a single fiber. Compared with unidirectional WDM systems, it not only saves the cost of deploying extra fibers, but also allows more flexible bandwidth provisioning. To exploit the advantages brought by this flexibility, we investigate path protection based on bi-directional WDM transmission system in this paper. With path protection, a call is accepted if and only if an active data path together with a disjointed backup path can be found in the network. With bi-directional WDM, backup resources sharing in both directions of a fiber is possible. To encourage resources sharing, new cost functions are judiciously designed. Based on them, two original path protection schemes are proposed in this paper, BiPro and BiProLP, where BiProLP aims at further economizing the hardware cost incurred by BiPro. In contrast to the traditional unidirectional schemes, we show that both BiPro and BiProLP can yield noticeably lower call blocking probability, higher system capacity and snorter active/backup path length. © 2005 IEEE.published_or_final_versio

    IP Restoration vs. WDM Protection: Is There an Optimal choice?

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