Optical networks employing wavelength division multiplexing (WDM) and wavelength routing are a potential candidate for future widearea networks. As these networks are prone to component failures and they carry a large volume of trafยฎc, providing fault tolerance capability to them is an important issue. This paper considers the problem of establishing dependable connections (D-connections) in wavelengthrouted wavelength-division multiplexed networks with dynamic trafยฎc demands. We call a connection with fault-tolerant requirements as a D-connection. We recommend using the pro-active approach wherein a D-connection is identiยฎed with the establishment of the primary lightpath and a backup lightpath at the time of honoring the request. Upon occurrence of a fault, a failed connection ยฎnds its backup path readily available.
We develop algorithms to select routes and wavelengths to establish D-connections with improved blocking performance. These algorithms differ in their performance and computational complexity. The algorithms use backup multiplexing technique to efยฎciently utilize the wavelength channels. To improve fairness between dependable and non-dependable connections, we propose a method called backup threshold. We conduct extensive simulation experiments on different networks to verify the effectiveness of the proposed algorithms.