Relieving Core Routers from Dynamic Routing with off-the-shelf Equipment and Protocols

Abstract: To answer traffic engineering goals, current backbone networks use expensive and sophisticated equipments, that run distributed algorithms to imple- ment dynamic multi-path routing (e.g., MPLS tunnels and dynamic trunk rerout- ing). We think that the same goals can be fulfilled using a simpler approach, where the core of the backbone only implements many a priori computed paths, and most adaptation to traffic engineering goals only takes place at the edge of the network. In the vein of Software Defined Networking, edge adaptation should be driven by a logically centralized controller that leverages the available paths to adapt traffic load balancing to the current demands and network status. In this article we present two algorithms to help building this vision. The first one selects sets of paths able to support future load balancing needs and adaptation to network faults. As the total number of required paths is very important, and their continuous availability requires many FIB entries in core routers, we also present a second algorithm that aggregates these paths in a reduced number of trees. This second algorithm achieves better results than previously proposed algorithms for path aggregation. To conclude, we show that off-the-shelf equipment supporting simple protocols may be used to implement routing with these trees, what shows that simplicity in the core can be achieved by using only trivially available proto- cols and their most common and unsophisticated implementation