SCOR: Software-defined Constrained Optimal Routing Platform for SDN

Abstract

While Software Defined Networks (SDN) has been introduced to facilitate innovation in networking, and to simplify the creation of new applications, there are domains in which these SDN promises are far from being realised. One such area is Quality of Service (QoS) routing and Traffic Engineering (TE). Despite the vital importance of QoS and TE in today’s networks, SDN currently does not provide sufficiently powerful abstractions and interfaces to facilitate the development of QoS and TE applications.This thesis addresses this gap by introducing a new northbound interface for SDN. A northbound interface provides the connection between network services and applications that use them. The northbound interface proposed here is based on constraint programming techniques to provide a robust, declarative interface for stating networking problems in SDN. It is called Software-defined Constrained Optimal Routing (SCOR) which is proposed with its corresponding routing framework in this thesis. This routing framework is based on SDN’s architecture model and uses SCOR as its northbound interface.The main advantage of SCOR, hiding the complexity of solving the problem from the user, is inherited from its constraint programming roots. Accordingly, the user only states the constraints and utility functions of the routing problem and the solution is provided by a powerful generic solver. SCOR is implemented in the MiniZinc constraint modelling language consisting of nine fundamental constraint programming predicates, which cover different aspects of the routing problems. It is shown that this interface (set of predicates) is sufficiently expressive to handle all the known and relevant QoS routing problems. Furthermore, the practicality and scalability of the approach are demonstrated via a number of example scenarios, with varying network topologies, network sizes and number of flows. Real-world applications are also modelled by implementing the proposed routing framework in a carrier-grade SDN controller, ONOS, to demonstrate the practical feasibility and benefits.