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The simulation results in [33] show that the MSPS scheme has better spare capacity
utilization and blocking performances than the OPP-DSP scheme.
4.3. Shared Source-Leaf Path-Based Protection (SLPP) [35]
In the SLPP algorithm, the primary tree in spares-splitting WDM networks can share
wavelengths with the backup paths without using any wavelength converters. In order to
reduce implementation cost, nodes are divided into two types: (1) Multicast Capable (MC)
that there are a small number of nodes in the network. MC is defined as a node which can
forward an incoming message to multiple output channels; and (2) Multicast Incapable (MI)
that cannot split the light.
Figure 13. An overview of MPSP. In the figure, S is the source node, and shaded nodes are
destinations. (a) illustration for spanning path; (b) deriving BP1;(c) deriving BP2; (d) deriving BP3; (e)
selecting backup paths; (f) resulted backup paths.
First a primary tree with some MC and MI nodes are considered. For each leaf node on
the primary tree, a link-disjoint backup path is discovered. Then all destinations on the
primary path from the source to a certain leaf node are determined and the circles are formed
by the primary and backup paths of the leaf node to protect these destination nodes. In order
to share a wavelength, the auxiliary graph G should be created from the primary tree P . For
this purpose, the SLPP algorithm is executed as follows:
The source node, the leaf nodes, and the MC nodes that are in P are located in G . Then, X
is set equal to G. The costs of links in X are initially set to infinity. The links involved in P are
removed from X . From each node to all other nodes in X , the shortest path is calculated. If
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