Guide to Disaster-Resilient Communication Networks by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 9783030446857
Publisher: Springer International Publishing

Let us focus on source node 1. Figures 16.1b-d present three different pairs of routing paths, each pair to a different combination of two anycast nodes. The minimum distance between each pair of routing paths is , and , respectively, as shown in Fig. 16.1. For example, in the pair of routing paths of Fig. 16.1b, a disaster of geographical coverage lower than can shut down both routing paths only if it covers both links a and e (the incident links of source node 1). Otherwise, the anycast nodes 3 and 5 guarantee that the anycast service will be maintained in the source node 1 for any disaster of geographical coverage lower than . Now, assume that . If the required D is lower than , all pairs of routing paths are feasible and the best solution is the one whose total cost of both paths is minimal. On the other hand, if , the only feasible solution is the pair of routing paths in Fig. 16.1d. Finally, if , none of the three solutions is feasible. In this case, either another set of anycast nodes enables the existence of a pair of paths with a minimum distance D or node 1 must be selected as an anycast node.

The method in [4] has a pre-processing phase. First, the distance between all network elements is computed based on the geographical information of the network. Then, for each node , the set of all pairs of links whose distance is lower than D is computed (special care is taken for link pairs sharing the source node since two of such links must be used whatever D is required). With all pre-computed sets , , an integer linear programming (ILP) model is proposed which can be solved by exact methods. The model guarantees that R nodes are selected as anycast nodes and that for each node : (i)if s is not selected as an anycast node, at most one link of each pair of links in is in the two routing paths from s to two different anycast nodes;

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