GCNav: Generic Configuration Navigation System

Configuration navigation and change-auditing is one of the most complex yet common tasks performed by network operators on a regular basis. Change-auditing router configuration files accurately is a challenging task due to presence of structure and hierarchy in the config content. Generic diff tools do not have the notion of context or syntactic structure while comparing files and produce diff reports (using minimum edit distance) that often do not match operator expectations. Moreover, these tools perform redundant (and expensive) comparison operations across contextually unrelated sections of the config file which makes them scale poorly even for config files of moderate size. On the other hand, vendor specific and customized diff solutions are not generic enough to be applied uniformly across a heterogeneous network. Also, modeling the configuration semantics for different vendors is a non-trivial and expensive process. In this paper, we introduce GCNav, a system that helps network operators perform general or customized change-auditing at varying levels of granularity on the network. Unlike existing solutions, GCNav makes use of the inherent syntactic structure common to all config files and thereby remains generic without compromising on the accuracy of results. Our experience with the deployment of GCNav on a large operational customer-facing IP network shows that it is able to provide a generic, accurate and scalable solution for change-auditing router config files. Our results show that GCNav’s diff results matches operator expectation while generic diff tools reported at least some misleading diff in 95% of the files analyzed. We also find that GCNav performs 7 times faster than customized auditing tools making it a feasible solution for online and interactive config auditing.