Periplus: A Resilient In-band SDN Control Plane via Embedded Forwarding Graphs
Many resource-constrained, wide-area telecommunications deployments could benefit from an in-band SDN control plane, but several challenges stand in the way. This paper presents Periplus, an in-band SDN control plane designed to address four challenges that this approach presents in such contexts: automatic bootstrapping, source-based routing, fast failure recovery, and multi-controller coordination. The first three are developed in detail, while multi-controller coordination is addressed in a separate paper. For bootstrap, Periplus avoids network-wide flooding: when a new switch joins, the controller installs flow rules in only two switches. For routing and failure recovery, Periplus encodes a primary path and per-hop alternatives in a graph structure encapsulated between L2 and L3 headers; switches forward along the primary path and, upon detecting a failure, fall over locally to the encoded alternative without controller involvement. We evaluate a Ryu-based implementation of Periplus in Mininet across multiple topologies. Periplus runs on stock Open vSwitch (OVS), relying only on its built-in Nicira extensions for Network Service Header (NSH) encapsulation. The evaluation shows sub-50 ms failure recovery, scalable bootstrap across topologies of varying size and diameter, and a per-switch flow-table footprint that is independent of network size and grows only at switches where the controller encodes multiple alternatives.