Static versus dynamic establishment of protection paths in WDM networks

Abstract

In wavelength division multiplexed networks (WDM) with 1:1 path protection, a link‐disjoint protection (backup) path is also set up at the time of setting up a working (primary) path. Hence, the failure of a single fiber‐link does not cause huge data losses. This paper considers on‐line routing and wavelength assignment (RWA) of protection paths in such networks. In particular, we study two strategies based on the 1:1 path protection scheme. The Static strategy establishes protection paths such that once a route and wavelength have been chosen they are not allowed to change. On the other hand, the Dynamic strategy allows for re‐arrangement of protection paths, that is, both the route and wavelength chosen for a protection path can change so as to accommodate a new request. With either strategy, we assume that the working paths cannot be re‐arranged. This is to prevent the disruption of on‐going traffic. The two strategies are compared on the basis of the number of connections requests that can be satisfied for a given number of wavelengths, assuming that the requests come one at a time, and wavelengths are assigned according to the First‐Fit policy. One of the results of our study is that, contrary to intuition, the Static strategy performs better than the Dynamic strategy.