The paper addresses the migration path and trade-offs involved in the evolution towards intelligent optical networks that allow scalable and flexible transport of a range of client formats and services. Disruptive all-optical switching and ultra-long reach WDM transmission technologies enable all-optical networks without opto-electronic conversion along paths that can span thousands of kilometers. Optical transport networks coupled with advances in distributed routing and signaling mechanisms are enabling the deployment of Automatically Switched Optical Networks (ASON). The paper discusses in detail the network architecture, optical switching capability, and network management and control architecture involved in the migration from existing and widely deployed WDM optical point-to-point systems to ASONs. The paper reports the findings of the Global Seamless Network (GSN) demonstrator at Deutsche Telekom, in which the concepts of intelligent optical transport networks are being demonstrated and evaluated. Further, a special emphasis is devoted to the question of managing survivability in ASONs. Simulation results comparing different approaches are presented, which illustrate the trade-off between dimensioning and performance of resilience mechanisms. The multi-layer integration between optical and higher layers is addressed from both a control plane and survivability perspective. Scenarios with different clients of the optical layer such as SDH and IP/MPLS are analyzed.