ProboScope: Data Plane Probe Packet Generation
Maciej Kuźniar, Peter Perešíni, Dejan Kostić · Infoscience (Ecole Polytechnique Fédérale de Lausanne) · 2014
Knowing if and when a particular forwarding rule has been installed in a switch is essential for understanding network behavior.This knowledge is missing in current Software Defined Networks, where the controller needs to ensure correct functioning of the network during forwarding state updates.Studies show that an absolute certainty about a rule's presence can be achieved only by exercising it in the data plane.In this work we describe ProboScope, a transparent layer at the controller that relies on carefully constructed data plane packets to provide reliable acknowledgments of rule installations.Driven by the theoretical underpinnings of the way probing rules and packets are constructed, we devise techniques that can generate probe packets in a variety of scenarios, in parallel with simultaneous rule installations, all while paying attention to the already installed rules.Our evaluation shows ProboScope's effectiveness and low overhead.Moreover, it demonstrates two important findings: (i) ProboScope can turn a buggy switch into a corrected one, and perhaps surprisingly (ii) ProboScope can increase the performance of a switch that delays barrier responses in an effort to ensure correct behavior.