Today's networks typically carry or deploy dozens of protocols and mechanisms simultaneously such as MPLS, NAT, ACLs and route redistribution. Even when individual protocols function correctly, failures can arise from the complex interactions of their aggregate, requiring network administrators to be masters of detail. The authors' goal is to automatically find an important class of failures, regardless of the protocols running, for both operational and experimental networks. To this end they developed a general and protocol-agnostic framework, called Header Space Analysis (HSA). Their formalism allows one to statically check network specifications and configurations to identify an important class of failures such as reachability failures, forwarding loops and traffic isolation and leakage problems.