Lightpath routing for intelligent optical networks

In this article, an overview of current issues and challenges in lightpath routine for optical networks is given. An architecture is presented in whic h optical switches are deployed, usually in the core, to interconnect IP ro uters at the edges. Lightpath routing within this architecture follows the framework of generalized multiprotocol label switching Our discussion pays particular attention to the aspects of optical routing that differ from rou ting in traditional IP networks. Such aspects include physical layer constr aints, wavelength continuity, the decoupling of control network topology fr om data network topology, explicit routing with wavelength assignment, and diversity routing for fast protection. We also present an algorithmic frame work for lightpath computation, highlighting the issue of wavelength contin uity and the differences between lightpath computation and traditional IP r oute computation.