  Software Defined Networking (SDN) brings numbers of advantages along with
many challenges. One particular concern is on the control-plane resilience,
while the existing protection approaches proposed for SDN networks mainly focus
on data-plane. In order to achieve the carrier-grade recovery from link
failures, we adopt the dedicated protection scheme towards finding optimal
protection routing for control-plane traffic. To this end, we study a weighted
cost minimization problem, in which the traffic load balancing and flow table
rule placement are jointly considered when selecting protection paths for
controller-switch sessions. Because this problem is known as NP-hard, we
propose a Markov approximation based combinatorial optimization approach for
routing protection in SDN control-plane, which produces near-optimal solution
in a distributed fashion. We then extend our solution to an on-line case that
can handle the single-link failure one at a time. The induced performance
fluctuation is also analyzed with theoretical derivation. Extensive
experimental results show that our proposed algorithm has fast convergence and
high efficiency in resource utilization.
