Coping with network failures has been recognized as an issue of major importance in terms of social security, stability and prosperity. It has become clear that current networking standards fall short of coping with the complex challenge of surviving failures. The need to address this challenge has become a focal point of networking research. In particular, the concept of tunable survivability offers major performance improvements over traditional approaches. Indeed, while the traditional approach is to provide full (100%) protection against network failures through disjoint paths, it was realized that this requirement is too restrictive in practice. Tunable survivability provides a quantitative measure for specifying the desired level (0%-100%) of survivability and offers flexibility in the choice of the routing paths. In this talk, we will focus on the implementation of this concept in two trasmition methods, namely unicast and broadcast.

For the unicasct method, we establish efficient algorithmic schemes for optimizing the level of survivability under additive end-to-end QoS bounds. Moreover,  we establish some (in part, counter-intuitive) properties of the optimal solution. For the broadcast method, we investigate the application of tunable survivability for e cient maintenance of spanning trees under the presence of failures and establish e cient algorithmic schemes for optimizing the level of survivability under various QoS requirements. In addition, we derive theoretical bounds on the number of required trees for maximum survivability. Finally, through extensive simulations, we demonstrate the e ectiveness of the tunable survivability concept for both methods.