Network function virtualization (NFV) is a paradigm focusing on increasing manageability and scalability of modern complex heterogeneous networks and network services by decoupling the network functions and hosting devices. However, as new promising solutions become available, the need for availability and reliability techniques grow, particularly for large-scale and interdependent scenarios. Therefore this book introduces three schemes to deploy risk-aware virtual function mapping and traffic routing to improve the reliability of user services as well as reduce deployment and routing costs. Results show that the implementation of risk-aware techniques may drastically reduce service outage, specially on random multi-failure scenarios.