The Evolution of Network Configuration: A Tale of Two Campuses

Studying network configuration evolution can improve our under- standing of the evolving complexity of networks and can be helpful in making network configuration less error-prone. Unfortunately, the nature of changes that operators make to network configuration is poorly understood. Towards improving our understanding, we examine and analyze five years of router, switch, and firewall con- figurations from two large campus networks using the logs from version control systems used to store the configurations. We study how network configuration is distributed across different network operations tasks and how the configuration for each task evolves over time, for different types of devices and for different loca- tions in the network. To understand the trends of how configura- tion evolves over time, we study the extent to which configuration for various tasks are added, modified, or deleted. We also study whether certain devices experience configuration changes more fre- quently than others, as well as whether configuration changes tend to focus on specific portions of the configuration (or on specific tasks). We also investigate when network operators make configu- ration changes of various types. Our results concerning configura- tion changes can help the designers of configuration languages un- derstand which aspects of configuration might be more automated or tested more rigorously and may ultimately help improve config- uration languages.