On Optimal Topology Verification and Failure Localization for Software Defined Networks.

We present a new set of solutions for topology verification and failure localization in Software Defined Networks SDNs. Our solutions are targeted towards offloading the control plane as much as possible and bringing more resilience against congestion or partitioning in the control plane. The core idea is to define control flows for network diagnosis and utilize a fraction of the forwarding table rules on the switches to serve these control flows. For topology verification, we present provably optimal or order-optimal solutions in total number of static forwarding rules and control messages. For single link failure localization, we present a solution that requires at least $3 \\vert {\\cal {\\bf E}}\\vert $ but at most $6 \\vert {\\cal {\\bf E}}\\vert $ forwarding rules using at most $1+\\log _{2}{ \\vert {\\cal {\\bf E}}\\vert }$ control messages, where $ \\vert {\\cal {\\bf E}}\\vert $ denotes the number of bidirectional links in the forwarding plane. We analyze the latency vs. rule and control message optimality trade-offs showing that sub-second failure localization is possible even in data center scale networks without significant additional overhead in the number of static rules and control messages. We further simulate the performance of failure localization in identifying multiple link failures.