IDEALIST control plane architecture for multi-domain flexi-grid optical networks

The IDEALIST (Industry-Driven Elastic and Adaptive Lambda Infrastructure for Service and Transport Networks) project has designed and implemented a Generalized Multi Protocol Label Switching (GMPLS) control plane for flexi-grid optical Dense Wavelength Division Multiplexing (DWDM) networks, providing significant input for IETF standardization. The control plane supports delegating the path computation function to dedicated Path Computation Elements (PCE), notably when justified by the limitations of the optical technology. This paper objectives are two-fold: to provide an overview of the major issues and challenges of the extension of such GMPLS/PCE control plane for multi-domain networks and to summarize the main architectural, functional and protocol choices. The architecture is based on the concept of domain topology abstraction and on the use of a stateful hierarchical PCE (H-PCE). The parent PCE coordinates the selection of domains and the multidomain provisioning using an abstracted view, and delegates the actual computation and actual intra-domain provisioning to the corresponding children PCEs. The parent abstracted view is constructed using the BGP-LS protocol (Border Gateway Protocol with Link State extensions) and end to end connectivity is obtained by concatenating Label Switched Paths (LSPs) segments, which are set up independently by the underlying GMPLS control plane at each domain.