NFReducer: Redundant Logic Elimination for Network Functions with Runtime Configurations

Network functions (NFs) are critical components in the network data plane. Their efficiency is important to the whole network's end-to-end performance. We identify three types of runtime redundant logic in individual NF and NF chains when they are deployed with concrete configured rules. We use program analysis techniques to optimize away the redundancy where we also overcome the NF specific challenges — we combine symbolic execution and dead code elimination to eliminate unused logic, we customize the common sub-expression elimination to eliminate duplicated logic, and we add network semantics to the dead code elimination to eliminate overwritten logic. We implement a prototype named NFReducer using LLVM. Our evaluation on both legacy and platform NFs shows that after eliminating the redundant logic, the packet processing rate of the NFs can be significantly improved and the operational overhead is small.