Time Dependent Diffusion Model for Security Driven Software Defined Networks

We present a model of a Software Defined Network (SDN)
where frequent changes in routing and traffic rates at routers are needed
to respond to the security, quality of service (QoS), and energy savings re-
quirements of applications such as the Internet of Things. Such frequent
path and traffic changes introduce time-dependent network behaviours,
and standard queueing models are not well adapted to analyse the tran-
sient regime, we propose a tractable diffusion approximation for both the
transient and steady-state behaviour. Our model can represent any net-
work topology transmitting time-dependent flows with routing changes,
and computes queue length and delay distributions at each network node
and along complete paths between senders and receivers. Using realistic
router parameters, we show that transients occupy a significant fraction
of system time, so that the optimisation conducted with SDN controllers
needs to include the effect of time-dependent behaviours.