The exponentially growing number of Internet users
armed with emerging multimedia Internet applications is continuously thirsty
for more network capacity. Wavelength-division multiplexing networks that
directly support IP-the so-called IP over WDM architecture-have the appropriate
characteristics to quench this bandwidth thirst. As everyday life increasingly
relies on telecommunication services, users become more and more demanding, and
connection reliability is currently as critical as high capacity. Both IP and
WDM layers can fulfill this need by providing various resilient schemes to
protect users' traffic from disruptions due to network faults. This article
first reviews the most common restoration and protection schemes available at
the IP and WDM layers. These schemes may be present concurrently in the IP over
WDM architecture, with the resilient mechanism of each connection specifically
chosen as a function of the overall cost, application requirements, and
management complexity. The second part of the article describes a versatile
heuristic based on simulated annealing that may be adopted to optimize the
concurrent use of IP restoration and WDM protection schemes in the same (mesh)
network. The proposed heuristic allows varying the percentage of traffic
protected by the WDM layer and that of traffic relying on IP restoration,
taking into account topology constraints and network cost minimization. An
additional feature of the proposed heuristic is the potential to trade solution
optimality for computational time, thus yielding fast solutions in support of
interactive design.