Source Prefix Filtering in ROFL

Traditional firewalls have the ability to allow or block traffic based on source address as well as destination address and port number. Our original ROFL scheme implements firewalling by layering it on top of routing; however, the original proposal focused just on destination address and port number. Doing route selection based in part on source addresses is a form of policy routing, which has started to receive increased amounts of attention. In this paper, we extend the original ROFL (ROuting as the Firewall Layer) scheme by including source prefix constraints in route announcement. We present algorithms for route propagation and packet forwarding, and demonstrate the correctness of these algorithms using rigorous proofs. The new scheme not only accomplishes the complete set of filtering functionality provided by traditional firewalls, but also introduces a new direction for policy routing.