The problem of disaster resilience is of paramount importance in today's telecommunication networks. Here, this problem is tackled by considering 1+1 optical lightpath protection with maximally SRLG-disjoint paths and geodiversity in a transparent backbone network. Geodiversity was added to make the network more resilient to geographically correlated disasters. The aim is to estimate the increase of the path lengths (fibre lengths) and the increase in cost of the required transponders, with respect to simple link disjointness (no-SRLG nor geodiversity constraints) in a fully transparent optical network. The results obtained in a realistic test network show that SRLG-disjointness already ensures an acceptable geodiversity for the considered network.

The resilience to disasters is a very relevant problem in telecommunication networks. This work addresses the problem of 1 + 1 optical lightpath protection considering maximally shared risk link group (SRLG)‐disjoint geodiverse paths, applied in the context of an optical network. The resilience to geographically correlated disasters is accomplished by guaranteeing geodiversity of the paths. This work focuses on estimating the increase of the path lengths and the increase in cost of the required transponders, compared to simple link‐disjointness (i.e., when no constraints on SRLG‐disjointness or geodiversity are considered). Results in different networks allow to evaluate the effect of SRLG‐disjointness to ensure some geodiversity.

Large scale natural disasters can have a profound effect on the telecommunication services in the affected geographical area. Hence, it is important to develop routing approaches that may help in circumventing damaged regional areas of a network. This prompted the development of geographically diverse routing schemes and also of disaster-risk aware routing schemes. A minimum-cost geodiverse routing, where a minimum geographical distance value D is imposed between any intermediate element of one path and any element of the other path is presented. Next the problem of the calculation of a D-geodiverse routing solution which ensures a certain level of availability is tackled. An algorithm is described that either obtains a solution to that problem or the most available path pair satisfying the desired geographical distance value D -this can be useful for the specification of availability levels in Service Level Agreements. Finally, a case study is presented, in an optical network, to determine the cost increase in terminal equipment (transponders) of approaches to ensure a much larger separation of the paths (of the selected path pair), with respect to minimal length link-disjoint routing. An Introduction to Geographically Diverse RoutingThe occurrence of large-scale disasters such as hurricanes, tsunamis, or earthquakes may cause a number of failures with a profound effect in the telecommunication services in a * This chapter is based on work from COST Action CA15127 ("Resilient communication services protecting end-user applications from disaster-based failures -RECODIS") supported by COST (European Cooperation in Science and Technology).