Conclusion Our contributions: Correctness constraints for configuration. Design and implementation of rcc. Study of configuration errors in real-world networks. Recommended protocol and language changes. http://nms.lcs.mit.edu/papers/rcc-tr.pdf rcc is available. More than 30 operators have downloaded the tool. Tested configurations of 9 ASes. http://nms.lcs.mit.edu/bgp/rcc/