East/Westbound Interfaces and Hierarchical Controller Designs

Investigate and define east/westbound interfaces among software-defined networking controllers, including their role in enabling hierarchical controller designs that achieve scalability, modularity, and security across distributed and multi-domain environments.

Background

The paper discusses modularity and flexible composition of controller platforms and notes gaps in how controllers interact horizontally (east/westbound) in distributed settings. Such interfaces are critical for data sharing, consistency models, and coordination across controller instances and domains.

The authors explicitly identify the need to further study east/westbound interfaces, particularly for hierarchical designs intended to scale and segment functionality and trust domains, making this a concrete open area of SDN controller research and standardization.

References

Other open issues to be further investigated in this context are the East/westbound APIs, and their use in enabling suitable hierarchical designs to achieve scalability, modularity, and security.

— Software-Defined Networking: A Comprehensive Survey  (1406.0440 - Kreutz et al., 2014) in Section: Controller Platforms — Modularity and Flexibility

An open problem is the coordination of governor state across multiple enforcement points in larger deployments.

— Autonomy in Check: Governor-Mediated Adaptive Security at the Edge  (2609.18338 - Ahmad et al., 16 Sep 2026) in Section 6, “Scope and Implications”