LIGHT TREE

91LIGHT TREESIT

Today, there is a general consensus that in near future wide area networks (WAN)(such as, a nation wide backbone network) will be based on Wavelength Division Multiplexed (WDM) optical networks.WDM comes under 3rd generation of network.The concept of light tree is introduced in a wavelength routed optical network, which employs wavelength -division multiplexing (WDM).

2 IntroductionSITA lightpath is a point-to-point all-optical wavelength channel connecting a transmitter at a source node to a receiver at a destination node.

A light-tree is a point-to-multipoint generalization of a lightpath.

3DefinationSITA light path is an all-optical channel, which may be used to carry circuit switched traffic, and it may span multiple fiber links.It assign a particular wavelength to fiber link .A light path can create logical (or virtual) neighbors .Light path communication employs equal no of transmitters and receivers .4Light pathSITIt extends the light path concept by incorporating optical multicasting capability .

Light tree enables single-hop communication between a source node and a set of destination nodes.5Light treeSIT6

SIT7

SIT8Light tree /Light path

Light path solution Transceivers Wavelengths

Light tree solution

Wavelengths 4 6 81.591.581.581.481.381.381.421.321.30 Transceivers 4 5 6 4 6 81.231.131.081.211.121.071.191.091.07 4 5 6SITMulticast capable wavelength routing switches (MWRS) .

More optical amplifiers in the network to maintain the optical signal power above a certain threshold .9Basic RequirementsSITPo1=(1-1)(1-3) Pi1+(1-2) 3Pi2 and Po2=1 (1-4) Pi1+14Pi210Multicast Switch

SITA physical topology for light tree can be given as :: Gp=(V,Ep) Gp: A weighted undirected graph V: Set of network nodes Ep: Set of links connecting nodes

The number of wavelength channels carried by each fiber =W. 11Problem FormulationSITAn NxN traffic matrix, where N is the number of network nodes and the (i, j) th element is the average rate of traffic flow from node i to node j.

The number of wavelength tunable lasers (Ti) and wavelength tunable filters (Ri) at each node. 12ContinuedSITA virtual topology Gp=(V, Ep) as another graph the out-degree of a node is the number of transmitters at the node the nodes of the virtual topology. In the virtual topology correspond to the nodes in the virtual topology, a link between nodes i, and j corresponds to a light tree rooted at node i with node j as one of the leaves on the light Tree.

13ObjectiveSITOptimization criterion Minimize one of the two objective functions:1:Average packet hop distance2:Total number of transceivers required in the network Constraints 1:Constraints arising from limited number of transceivers per node.2:Constraints arising from limited number of wavelengths.3:Constraints arising from the limited bandwidth of light tree.

14Optimization of LIGHT TREE ProblemSITEnables single-hop communication between a source node and a set of destination nodes. A light tree based virtual topology can significantly reduce the hop distance, thereby increasing the network throughput.Enormous bandwidth of an optical fiber (up to 50 terabits bits per second) because of WDM 15Advantages Light tree over Light pathSITLight trees is capable of supporting broadcasting and multicasting over a WAN by employing a minimum number of opto-electronic devices Preliminary results show that if we employ a set of light trees, then significant savings can be achieved in terms of the number of opto- electronic devices that are required in the network.

16ConclusionSITwww.ieng.com/univercd/cc/td/doc/product/softwareswww.seminartopics1.blogspot.com/2007/06/light-tree.html www.ieeexplore.ieee.org/iel5/8585/27205www.springerlink.com/index www.dspace.cusat.ac.in/dspace/bitstream17ReferencesSIT18 ANY QUERIES ?

SIT19 THANK YOU