Maintaining Colored Trees for Disjoint Multipath Routing Under Node Failures

Colored Trees (CTs) is an efficient approach to route packets along link- or node-disjoint paths in packet-switched networks. In this approach, two trees, namely red and blue, are constructed rooted at a drain such that the path from any node to the drain are link- or node-disjoint. For applications where both the trees are used simultaneously, it is critical to maintain the trees after link or node failures. To this end, this paper develops an algorithm, referred to as SimCT, that efficiently constructs and maintains colored trees under failures using only local information. Even when the entire tree needs to be recomputed, the SimCT algorithm requires 40% lesser messages than previous techniques. The convergence time of the SimCT algorithm is linear in the number of nodes. We show through extensive simulations that the average length of the disjoint paths obtained using the SimCT algorithm is lesser compared to the previously known techniques. The above-mentioned improvements are obtained by exploiting the relationship between DFS numbering, lowpoint values, and the potentials employed for maintaining partial ordering of nodes. The SimCT algorithm is also extended to obtain colored trees in multi-drain networks.