Rotational Bridge Priority Masking for Building Equal-Cost Multi-tree

Abstract

The routing in ethernet backbone networks chooses large number of shortest paths on purpose and establishes multiple shortest path trees for the better load balancing and faster protection by using the bridge priority masking method. This simple and nice method, however, does not permit bit position change, resulting in bitwise unfairness in the choice of paths. This paper raises an open mathematical bridge priority masking problem that allows any kind of bit permutation, and gives two solutions under our proposed 8-way rotation with inversion, and proves that only two solutions exist. According to the performance evaluation using total path inspection, a proposed rotational solution enhances the fairness in choosing paths by 8–43 % than the current one.