Coordinated Computation and Setup of Multi-layer Paths via Inter-layer PCE Communication: Standards, Interoperability and Deployment

The IETF Path Computation Element (PCE) framework is a prime example of a software-defined network virtualisation artifact, originally envisaged about a decade ago for constraint-based routing in the conventional best-effort Internet. Over the years, however, it evolved into the ultimate tool for multi-technology, multidomain, multi-layer, and multi-vendor networking. Carriers have already started to implement PCE-based solutions in their combined Internet IP/MPLS and Wavelength Switched Optical Networks (WSONs). However, significant development and testing is still needed to elevate the PCE concepts from theory to practice. This paper addresses standards, interoperability and deployment of coordinated computation and setup of multi-layer paths from a practical perspective and presents its first implementation in a multi-vendor, interoperable PCE testbed. In our testbed, we try to push the limits of multivendor interoperability, which current research mostly neglects, and thereby identify missing links in the current research and standards necessary to implement and deploy inter-operable multi-layer systems. We point to the key areas that the research and industrial communities will need to address in making the proposed solutions practical, which in turn will drive the upcoming efforts in software-defined networking with inter-operable PCE-based architectures.