Safe Updates of Hybrid SDN Networks

Software Defined Networking (SDN) promises to bring unparalleled flexibility, fine-grained control, configuration simplification and no vendor lock-in. The introduction of SDN in an existing network, however, must be incremental in most cases, for both technical and economical reasons. During the transition, operators have to manage hybrid networks, where SDN and traditional protocols coexist. In this paper, we show that the simultaneous presence of SDN and traditional routing protocols can create forwarding anomalies that ultimately defeat the purpose of deploying SDN. We devise techniques to adapt traffic flows to network dynamics, update routing policies and incrementally deploy SDN in hybrid networks, while avoiding those anomalies. We assess the applicability of our approach by extensive simulations. By adding support for manageability and evolvability, our techniques make hybrid networks not only a means for transition but also an interesting design point that can merge advantages of SDN and traditional paradigms.