A Polynomial-Time Algorithm for ComputingDisjoint Lightpaths Pairs in MinimumIsolated-Failure-Immune WDM Optical Networks

ABSTRACT

A fundamental problem in survivable routing inwavelength division multiplexing (WDM) optical networks is thecomputation of a pair of link-disjoint (or node-disjoint) lightpathsconnecting a source with a destination, subject to the wavelengthcontinuity constraint. However, this problem is NP-hard whenthe underlying network topology is a general mesh network. As a result, heuristic algorithms and integer linear programming (ILP)formulations for solving this problem have been proposed. Inthis paper, we advocate the use of 2-edge connected (or 2-nodeConnected) subgraphs of minimum isolated failure immune networksas the underlying topology for WDM optical networks.We present a polynomial-time algorithm for computing a pair ofLink-disjoint lightpaths with shortest total length in such networks.

INTRODUCTION:Optical networks implemented using wavelengthdivision multiplexing (WDM) techniques are consideredpromising candidates for backbone high-speed widearea networks. Among other things, wavelengthrouting allows logical topologies to be built on top of physicaltopologies to reflect the traffic intensities between the variousnodes as well as to provide reliable services by allowing forreconfiguration in the event of failures.In a WDM optical network, each fiber link can carry manywavelengths. A WDM network is modeled by an undirectedgraph , where is the set of vertices, denotingnodes in the network; is the set of edges, denoting links (oroptical fibers) in the network; is the set ofwavelengths, and is the set of wavelengths availableon link . The terms vertices and nodes are used interchangeably,as well as edges and links. In this model, each undirectededge in the network represents a bidirectional link connection. Whenever a link is used by a connection, it isoccupied in both directions.In WDM networks, data packets are transmitted along lightpaths. A lightpathsbetween nodes andon wavelength is an path in thatuses wavelength on every link of path. We assumethat the nodes do not have wavelength converters, and as a consequence, each lightpaths must maintain the same wavelengththroughout the entire path. This is known as the wavelength continuity constraint.Cuts in fibers are one of the most common failures in opticalnetworks, while failures of routers are also possible. Sinceoptical links carry a very high volume of data, survivabilityis important. Hence, survivable lightpaths routing has beenextensively studied. In the rest of this section, we give a briefoverview of survivable lightpaths routing, introduce minimumisolated failure immune networks, state the problem to bestudied and our contributions, and differentiate our work fromclosely related work.Disjoint Lightpaths Routingto tolerate a single link (node, respectively) failure inthe network, the path protection scheme of fault managementestablishes an active lightpathsand a link-disjoint(node-disjoint, respectively) backup lightpaths, so that in theevent of a link failure (node failure, respectively) on the activelightpaths, data can be quickly rerouted through the backuplightpaths. In the dedicated path protection scheme, each activelightpaths has a dedicated backup lightpaths no two backup lightpaths share a common link on a common wavelength. Inthe shared path protection scheme, two backup lightpathsmay share a common link on a common wavelength, as long as the corresponding active lightpaths do not share a commonlink.Isolated Failure Immune NetworksIn order to provide network survivability, a price to pay isredundancy. Complete graphs offer the most survivability, but have the highest redundancy. Trees have no redundancy (amongconnected networks), but offer no survivability. A ring networkcan survive a single node failure or a single link failure, but cannot survive two link failures.Farleystudied an important class of networks, which can survive many simultaneous node and link failures, as longas they are isolated. Here, two node failures are isolated if thenodes are not adjacent; two link failures are isolated if the links do not meet at a node; a node failure and a link failure are isolatedif the failed link is not incident to the failed node.Definition 1.2 (IFI Networks): A network is said to be isolated-failure-immune (IFI) if all pairs of functional nodes canstill communicate, as long as the failures are pairwise isolated.An IFI network is called a minimum IFI network if it has theminimum number of links among all IFI networks on the samenumber of nodes.

PROBLEM DEFINITION

1. Optical Network is that effective in real time.

1. Wavelength Division Multiplexing(WDM) techniques based Authentication is not achieved so far.

1. Networks implementation is spoken in the base paper.

EXISTING SYSTEM:In the EXISTING SYSTEM, they are fault-tolerant to multiple failuresas long as the faults are isolated. Minimum IFI networksare attractive because they are scalable and often admit simplesolutions to many networking problems.

PROPOSED SYSTEM:In the PROPOSED System,besides providing guidelines for the design of future survivable optical networks, our work can have an impact on improved decision making in existing optical networks. While the backbone of existing optical networks may not be subgraphs of minimum IFI networks, we can compute a subgraph of the given network that has the structure assumed in this paper. Using offline computation, by hidinga few network links so thatthe resulting network has no subgraph that is homeomorphic tothe four-vertex complete graph. Our algorithm can beapplied to this resulting network, while the links that have been hidden in the above process can be used to provide additionalprotection.

SYSTEM SPECIFICATIONHardware Requirements1. Processor:Pentium IV1. RAM:512 MB1. HDD:80 GB

Software Requirements1. Platform:Windows Xp1. Front End:DOT NET1. Back End:MS SQL server

CONCLUSIONWe have presented a polynomial-time algorithm for computinga pair of link-disjoint lightpaths in a WDM optical networkwhose underlying topology is a subgraph of a minimumIFI network. Our algorithm can be easily modified to computea pair of node-disjoint lightpaths in such networks.IFI networks have received a lot of attention in the literaturebecause they are fault-tolerant to multiple failuresas long as the faults are isolated. Minimum IFI networksare attractive because they are scalable and often admit simplesolutions to many networking problems. Besidesproviding guidelines for the design of future survivable opticalnetworks, our work can have an impact on improved decisionmaking in existing optical networks.While the backbone of existingoptical networks may not be subgraphs of minimum IFInetworks, we can compute a subgraph of the given network thathas the structure assumed in this paper. This can be achieved,using offline computation, by hiding a few network links so thatthe resulting network has no subgraph that is homeomorphic tothe four-vertex complete graph. Our algorithms can beapplied to this resulting network, while the links that have been hiddenin the above process can be used to provide additionalprotection.

REFERENCES[1] S. Ahuja, S. Ramasubramanian, and M. Krunz, SRLG failure localizationin all-optical networks using monitoring cycles and paths, inProc. IEEE INFOCOM, 2008, pp. 700708.[2] V. Anand and C. Qiao, Static versus dynamic establishment of protectionpaths in WDM networks, J. High Speed Netw., vol. 10, pp.317327, 2001.[3] R. Andersen, F. Chung, A. Sen, and G. Xue, On disjoint path pairswith wavelength continuity constraint in WDM networks, in Proc.IEEE INFOCOM, 2004, pp. 524535.[4] D. Banerjee and B. Mukherjee, Wavelength-routed optical networks:Linear formulation, resource budgeting tradeoffs, and a reconfigurationstudy, IEEE/ACM Trans. Netw., vol. 8, no. 5, pp. 598607, Oct. 2002.[5] R. Banner and A. Orda, The power of tuning: A novel approach forthe efficient design of survivable networks, IEEE/ACM Trans. Netw.,vol. 15, no. 4, pp. 737749, Aug. 2007.[6] H. F. Beltran and D. Skorin-Kapov, On minimum cost isolated failureimmune networks, Telecommun.Syst., vol. 3, pp. 183200, 1994.[7] I. Chlamtac, A. Ganz, and G. Karmi, Lightpath communications: Anapproach to high bandwidth optical WANs, IEEE Trans. Commun.,vol. 40, no. 7, pp. 11711182, Jul. 1992.[8] H. Choi, S. Subramaniam, and H. A. Choi, On double-link failurerecovery in WDM optical networks, in Proc. IEEE INFOCOM, 2002,pp. 808816.[9] C. J. Colbourn and G. Xue, Grade of service Steiner trees in seriesparallelnetworks, in Advances in Steiner Trees, D. Z. Du, J.M. Smith,and J. H. Rubinstein, Eds. Norwell, MA, USA: Kluwer, 2000, pp.163174.