Multipath policy routing for the inter-domain scenario

Abstract

Multipath routing can provide a better solution for several of the current BGP's problems in the inter-domain scenario by allowing a cleaner separation between routing and traffic engineering and better failure containment. The separation between routing control logic and data forwarding, and the use of software defined networking principles open space to easier deployments of new routing protocols at the inter-domain level. This paper explores the potential of using a multipath policy based inter-domain routing algorithm based on an algebraic model. The algorithm establishes multiple paths to a destination following a policy-based architecture and works with simple destination-based hop-by-hop forwarding. We focus on the definition of algebraic models for the links, their composition and the resulting path's ranking. Our algorithm addresses the most common situations in the Internet and we include others not so common as backup links and sibling relations. We prove the correctness of the algorithm under conditions that open several implementation options and describe how it can use multipath for failure containment, using the extra paths to make each failure less important. The paper finishes with the presentation of some experimental results that illustrate the algorithm capabilities.

Achieving Correct Hop-by-Hop Forwarding on Multiple Policy-Based Routing Paths

“…In [14] we used our results to design a routing algorithm suitable for the inter-domain scenario and in [15] we described an architecture for a Layer 2 fabric that uses a path finding algorithm with policies and multipath forwarding that was designed using this work and implemented using Openflow and an SDN controller. Both works constitute examples of the flexibility that our findings can bring in terms of the number of usable paths and illustrate possible applications of protocols designed with this new correctness conditions.…”

“…Paths with the same policy attributes can all be considered of equal preference (we want to treat them in the same way) even if they have quite different metrics (like hops, bandwidth or delay) opening the possibility to have more path diversity. Multipath policy based protocols can find applications in such diverse scenarios as Internet routing [14] or layer 2 fabrics in data center networks [15] where multipath (even without formal guarantees of mutual exclusion of paths) alleviates several problems.…”