Software network functions (NFs), or middleboxes, promise flexibility and easy deployment of network services but face the serious challenge of unexpected performance behaviour. This behaviour makes it harder for network operators to provision their networks and exposes a new attack surface for adversaries seeking to degrade network performance. The goal of our work is to provide network operators and NF developers with comprehensive understanding of the NF’s entire performance profile, before it is deployed. Such understanding would, for instance, allow operators to conduct precise capacity planning and developers to make informed development decisions.

We propose the notion of performance contracts for NFs. A performance contract enables users to predict and scrutinize NF performance at fine granularities without having to run them. It provider users with an abstraction that enables them to easily parameterize arbitrary input workloads, whether typical, exceptional or adversarial. Given only this abstract description of the workload and not a concrete instance, the contract predicts the performance of the NF without actually running it. The performance predictions are in terms of human-readable formulae, expressed as a function of workload and environment variables, that we together call Performance Critical Variables (PCVs). informed development decisions.