Modern Web-enabled multimedia conferencing systems relays the source video flows to all call participants through media conferencing servers. This solution works well for small conference groups. However, as the conference size increases, the outbound bandwidth of the conferencing server becomes the bottleneck, which limits the scalability of the system and eventually degrades conference QoS. In this paper, we re-architect the multimedia conferencing service using Software-Defined Networks (SDN) that provides enhanced scalability and service orchestration. The main idea of our approach is to decouple the data plane and the control plane of the conferencing service. We advertise the group-based traffic forwarding capability of commodity OpenFlow switches as OpenFlow Selective Forwarding as a Service (OFSFaaS). The conferencing server now only handles control traffic, and dynamically establish media channels using OpenFlow switches through OFSFaaS. Preliminary prototype evaluations show that OFSFaaS eliminates the outbound bottleneck at conferencing servers and scales efficiently. OFSFaaS can be subscribed to by a wide range of multimedia services.