Traffic engineering has become a central topic in contemporary public IP networks, driven by economic considerations and the competitive aspiration on the part of network service providers to reduce operational expenditures, improve service quality, and increase revenue. Internet traffic engineering deals with the performance optimization of operational IP networks, encompassing the application of technology and scientific principles to network planning, dimensioning, and dynamic control. The key concepts developed in this paper center around the notion of "integrated traffic engineering," which embraces a broader and more holistic view of operational network performance enhancement when compared with conventional traffic engineering, especially in IP over Optical (IPO) networks. Integrated traffic engineering refers to a new philosophy of collaborative decision making geared towards operational network performance optimization that involves simultaneous consideration of various control and management capabilities at different levels in the network hierarchy. Integrated traffic engineering is intended to increase network capacity, performance, efficiency, and survivability while reducing costs. This paper discusses the fundamental concepts of integrated traffic engineering in IPO networks.