Information Technology Reference

In-Depth Information

Figure 12. Reviewed multicast protection algorithms.

4.1. Dynamic Multicast Protection Schemes

Two algorithms are suggested to reduce the session blocking probability and to decrease

the usage of network resources by removing or avoiding residual links in the topology that

consists of “light-tree” and its backup path.

4.1.1. Optimal Path-Pair Based Removing Residual Link (OPP-PRL) [32]

The OPP-PRL algorithm is derived from the Optimal Path-Pair based Shared Disjoint

Path (OPP-SDP). The OPP-SDP algorithm computes an optimal path pair between a source

and destination pair. In the OPP-PRL algorithm, a link-disjoint path pair is found for each

destination node. Using this algorithm, residual links between the source and destination can

be removed. In order to minimize additional costs and to increase sharing of new path pair

with those found previously, the OPP-SDP algorithm updates the cost to zero for the links

along the found path. Moreover, this algorithm decreases the usage of network resources by

removing the overlapping path and straddling path. However, paths are removed under two

conditions: (1) if there are two link disjoint paths, except the overlapping path. Moreover,

there is not any destination node in the overlapping path; and (2) there is not any destination

node in the straddling path. Results in [32] show that OPP-PRL can improve blocking

probability about 10% over OPP-SDP when traffic load is high.

4.1.2. Source-Leaf Path Based Avoiding Residual Link (SLP-ARL) [32]

In SLP-ARL, a primary tree is first created for a given multicast session, and then the

backup paths are found for the primary tree in order to avoid having residual links in the

procedure of finding backup paths for a given working tree. Therefore, we can say that there

are two stages in the SLP-ARL algorithm. In the first stage, a multicast routing algorithm is

used to create a primary tree in order to reduce the number of leaf nodes on the multicast tree.

Then, a backup path is derived for each destination node at the second stage. Hence, in this

algorithm, backup paths are only setup for the leaf nodes on the primary tree. Note that the

backup path and working path for a leaf node can overlap on some links, which have been