Optimising packet forwarding in multi-tenant networks using rule compilation

Packet forwarding in Software-Defined Networks (SDN) relies on a centralised network controller which enforces network policies expressed as forwarding rules. Rules are deployed as sets of entries into network device tables. With heterogeneous devices, deployment is strongly bounded by the respective table constraints (size, lookup time, etc.) and forwarding pipelines. Hence, minimising the overall number of entries is paramount in reducing resource consumption and speeding up the search. Moreover, since multiple control plane applications can deploy own rules, conflicts may occur. To avoid those and ensure overall correctness, a rule validation mechanism is required. Here, we present a compilation mechanism for rules of diverging origins that minimises the number of entries. Since it exploits the semantics of rules and entries, our compiler fits a heterogeneous landscape of network devices. We evaluated compiler implementations on both software and hardware switches using a realistic testbed. Experimental results show a reduction in both produced table entries and forwarding delay.