  Software-Defined Networking (SDN) has raised the boundaries of cloud
computing by offering unparalleled levels of control and flexibility to system
administrators over their virtualized environments. To properly embrace this
new era of SDN-driven network architectures, the research community must not
only consider the impact of SDN over the protocol stack, but also on its
overlying networked applications. In this big ideas paper, we study the impact
of SDN on the design of future message-oriented middleware, specifically
pub/sub systems. We argue that key concepts put forth by SDN can be applied in
a meaningful fashion to the next generation of pub/sub systems. First, pub/sub
can adopt a logically centralized controller model for maintenance, monitoring,
and control of the overlay network. We establish a parallel with existing work
on centralized pub/sub routing and discuss how the logically centralized
controller model can be implemented in a distributed manner. Second, we
investigate the separation of the control and data plane, which is integral to
SDN, which can be adopted to raise the level of decoupling in pub/sub. We
introduce a new model of pub/sub which separates the traditional publisher and
subscriber roles into flow regulators and producer/consumers of data. We then
present use cases that benefit from this approach and study the impact of
decoupling for performance.
