Detecting BGP Configuration Faults with Static Analysis

The Internet is composed of many independent autonomous systems (ASes) that exchange reachability information to destinations using the Border Gateway Protocol (BGP). Network operators in each AS configure BGP routers to control the routes that the routers learn, select, and announce to other routers. Faults in BGP configuration can cause forwarding loops, packet loss, and unintended paths between hosts, all of which constitute failures of the Internet routing infrastructure. This paper describes the design and implementation of rcc, the router configuration checker, a tool that finds faults in the BGP configurations of routers in an AS using static analysis. rcc detects two broad classes of faults that affect network reachability: route validity faults, where routers may learn routes that do not correspond to usable paths, and path visibility faults, where routers may fail to learn routes for paths that exist in the network. rcc enables network operators to test and debug configurations before deploying them in an operational network, improving on the status quo where most faults are detected only during operation. rcc has been downloaded by more than sixty network operators to date, some of whom have shared their configurations with us. We analyze network-wide configurations from 17 different ASes to detect both faults that induce failures and faults that are benign.