A difference resolution approach to compressing Access Control Lists

Access Control Lists (ACLs) are the core of many networking and security devices. As new threats and vulnerabilities emerge, ACLs on routers and firewalls are getting larger. Therefore, compressing ACLs is an important problem. In this paper, we propose a new approach, called Diplomat, to ACL compression. The key idea is to transform higher dimensional target patterns into lower dimensional patterns by dividing the original pattern into a series of hyperplanes and then resolving differences between two adjacent hyperplanes by adding rules that specify the differences. This approach is fundamentally different from prior ACL compression algorithms and is shown to be very effective. We implemented Diplomat and conducted side-by-side comparison with the prior Firewall Compressor algorithm on real life classifiers. The experimental results show that Diplomat outperforms Firewall Compressor most of the time, often by a considerable margin. In particular, on our largest ACLs, Diplomat has an average improvement ratio over Firewall Compressor of 30.6%.