Minimizing Update Makespan in SDNs Without TCAM Overhead

Efficient and consistent update of the network routing rules is a challenging task that significantly affects the performance, correctness, and security of Software-Defined Networks (SDN). In this work, we consider the problem of minimizing the makespan of updating the routing rules in SDNs, while guaranteeing three crucial consistency requirements: (1) WayPoint Enforcement, (2) Loop Freedom, and (3) Conflict Freedom. This problem is known to be NP-hard, and thus we focus on designing approximate algorithms that run in polynomial time without incurring TCAM storage overhead. To compute consistent rule-update schedules, we propose two algorithms, called
TimeX
and
RMS
.
TimeX
employs the solution of a linear program (LP) to address the makespan minimization goal systematically.
RMS
is an LP-independent heuristic that provides higher scalability. We demonstrate and utilize a property of rule-updates, called reversibility, to reduce the makespan in RMS. Extensive simulations show that our algorithms reduce the makespan by 2% to 18% and attain a 4.9
$\times$
speedup compared to previous studies. Moreover, Mininet experiments reveal that the proposed algorithms can mitigate the transient congestion caused by conflicting flows.