Controller-agnostic SDN Debugging.

Complexity in software-defined network (SDN) applications calls for methods and tools that can facilitate comprehensive debugging and analysis. A key challenge in this regard is that SDN configurations interact with network devices that can behave in unexpected ways, depending on factors such as traffic and application mix. In this paper, we describe OFf, a debugging and test environment for SDN developers. OFf is built on top of the fs-sdn simulator, which was developed to offer simple-to-use, accurate and scalable evaluation of OpenFlow-based SDN configurations. OFf offers standard debugging features for controller applications such as stepping, breakpoints, and watch variables. It also offers features that provide visibility into network behavior including packet tracing, packet replay and visualization features, and alerts that are triggered when, e.g., configurations change. OFf is accessed through a text interface and is designed to interoperate with any standard SDN controller platform. We demonstrate the capabilities of OFf through three test scenarios that illustrate its utility and modest performance impact on running applications. Specifically, we show how OFf can be used to analyze and fix bugs in a traffic engineering application, and to detect and repair a security vulnerability due to multiple application interaction and unexpected rule expiration.