Routing reliability analysis of partially disjoint paths

Alternative paths may significantly improve routing reliability in an IP network, One application of this technique is to enhance the reliability of the popular open shortest path first (OSPF) routing protocol. In our proposed reliable OSPF (ROSPF) routing protocol, one primary path and two alternate backup paths are deployed for data transmission. As expected, the number of shared links and routers among the three paths dominates the reliability of the routing connection between two routers. The calculation of routing reliability of multiple paths is very important in alternate path-finding algorithms. To solve this problem, we use the Venn diagram model to analyze the overall failure probability of three partially disjoint paths and to understand how the double- and triple-shared links affect the routing reliability. General mathematical formulas to calculate the failure probability are also obtained.