LIGHT TREE

1. SIT LIGHTTREE 9

2. SIT Introduction • 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).

3. SIT Defination • A 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.

4. SIT Light path • A 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 .

5. SIT Light tree • It 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.

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8. SIT Light tree /Light path

9. SIT Basic Requirements • Multicast –capable wavelength routing switches (MWRS) . • More optical amplifiers in the network to maintain the optical signal power above a certain threshold .

10. SIT Multicast Switch • Po1=(1-α1)(1-α3) Pi1+(1-α2) α3Pi2 and Po2=α1 (1-α4) Pi1+α1α4Pi2

11. SIT Problem Formulation • A 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.

12. SIT Continued… • An 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.

13. SIT Objective • A 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.

14. SIT Optimization of LIGHT TREE Problem • Optimization criterion – Minimize one of the two objective functions: 1:Average packet hop distance 2: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.

15. SIT Advantages Light tree over Light path • Enables 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

16. SIT Conclusion • Light 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.

17. SIT References… • www.ieng.com/univercd/cc/td/doc/product/softwares • www.seminartopics1.blogspot.com/2007/06/light-tree.html • www.ieeexplore.ieee.org/iel5/8585/27205 • www.springerlink.com/index • www.dspace.cusat.ac.in/dspace/bitstream

18. SIT ANY QUERIES ……?

19. THANK YOU