Online video streaming is becoming a key consumer of future networks, generating high-throughput and highly dynamic traffic from large numbers of heterogeneous user devices. This places significant pressure on the underlying networks and can lead to a deterioration in performance, efficiency and fairness. To address this issue, future networks must incorporate contextual network designs that recognise application and user-level requirements. However, designs of new network traffic management components such as resource provisioning models are often tested within simulation environments which lack subtleties in how network equipment behaves in practice. This paper contributes the design and operational guidelines for a Software-Defined Networking (SDN) experimentation framework (REF), which enables rapid evaluation of contextual networking designs using real network infrastructures. Two use case studies of a Quality of Experience (QoE)-aware resource allocation model, and a network-aware dynamic ACL demonstrate the effectiveness of REF in facilitating the design and validation of SDN-assisted networking.