Composing middlebox and traffic engineering policies in SDNs

Middleboxes present new requirements that need to be integrated with traffic engineering applications that are already complex and consider myriad factors (e.g., routing, QoS, load-balancing). While it is possible to revisit traffic engineering algorithms to explicitly integrate middleboxes, such an approach is not compositional. Existing efforts at compositional SDN application development do not apply since they support application composition after static packet-forwarding policies are generated by application modules. Consequently, routes computed by a traffic engineering module cannot be influenced by the constraints imposed by a module that specifies middlebox traversal requirements. In this paper, we explore an alternate approach where application composition is done prior to the generation of packet-forwarding policies. Each application is written as a logic program, and provides a set of requirements that must be respected by a synthesized solution. A constraint solving engine iterates over these requirements to search the solution space and find a solution respecting all the requirements. We illustrate our approach with a concrete case study, and implement it using the Z3 SMT solver [1]. Our initial results point to the promise of the approach.