Telekinesis: controlling legacy switch routing with OpenFlow in hybrid networks

Hybrid networks contain both legacy and programmable network switches and allow operators to reap the benefits of Software-defined networking (SDN) without upgrading the entire network. Previous research shows that adding SDN capabilities to switches at strategic places in a network and ensuring that each flow traverses at least one such switch is sufficient to achieve many SDN control paradigms, such as routing or access control. However, the control points are still limited to the SDN-enabled devices and operators cannot enforce fine-grained policies on the legacy paths between SDN switches. We present Telekinesis, a network controller that enables finer-grained routing control over legacy paths in hybrid networks using OpenFlow. To update routing entries in legacy switches, we introduce a new flow control primitive, LegacyFlowMod. LegacyFlowMod uses OpenFlow's PacketOut function to send a special packet on a specific interface of a legacy switch and remotely manipulate the forwarding entry associated with the source of the packet. Using simulations on random network topologies with varying degrees of OpenFlow deployment, we show that Telekinesis can provide more diverse path control than an OpenFlow-only controller: even when only 20% of switches are OpenFlow-enabled, we can update 70% of the paths.