WNetKAT: A Weighted SDN Programming and Verification Language

Programmability and verifiability lie at the heart of the software-defined networking paradigm. While OpenFlow and its match-action concept provide primitive operations to manipulate hardware configurations, over the last years, several more expressive network programming languages have been developed. This paper presents WNetKAT, the first network programming language accounting for the fact that networks are inherently weighted, and communications subject to capacity constraints (e.g., in terms of bandwidth) and costs (e.g., latency or monetary costs). WNetKAT is based on a syntactic and semantic extension of the NetKAT algebra. We demonstrate several relevant applications for WNetKAT, including cost- and capacity-aware reachability, as well as quality-of-service and fairness aspects. These applications do not only apply to classic, splittable and unsplittable (s; t)-flows, but also generalize to more complex network functions and service chains. For example, WNetKAT allows to model flows which need to traverse certain waypoint functions, which may change the traffic rate. This paper also shows the relation between the equivalence problem of WNetKAT and the equivalence problem of the weighted finite automata, which implies undecidability of the former. However, this paper also succeeds to prove the decidability of another useful problem, which is sufficient in many practical scnearios: whether an expression equals to 0. Moreover, we initiate the discussion of decidable subsets of the whole language.