The challenge arises if the different network domains use different technologies. In this case, we have a multi-layer path finding problem.
We will show that there are situations where algorithms as used in single layer networks, such as BGP, SS7 and OSPF-TE, cannot find the shortest path. A shortest path in a multi-layer network can contain loops, and a segment of a shortest path may not be a shortest path in itself.
To solve this problem, both a multi-layer network representation as well as new path finding algorithms need to be developed. An additional challenge is to make a generic path finding algorithm that is technology-independent, and does not need to be modified as new technologies emerge.
We show that it is possible to create solutions for all three problems. Using RDF-based techniques, we model multi-layer networks and describe incompatibilities for the path finding algorithm in technology-independent way. We also present a path finding algorithm that is able to use this information to find valid paths.