Topology-Preserving Traffic Engineering for Hierarchical Multi-Domain SDN

Decoupling of control and data plane in Software Define Networks (SDN) creates significant flexibility in network management. As networks are evolving into a complex multi-domain multi-layer architecture, traffic engineering across multiple domains and layers entails significant challenges for the control plane, especially when each separate administrative domain is not willing to disclose its network topology and resource information. In this paper, we present the first traffic engineering scheme for a multi-domain SDN by using a hierarchical control plane, in which each domain is managed by a local controller, and they are further controlled by a centralized root controller. To preserve the local topology of each domain, we extend the Network Information Base (NIB) into a hierarchical architecture as well, and the root controller maintains only an abstracted view of the lower-layer networks in its NIB. Then, we devise a communication protocol, which enables controllers at different layers and domains to work collaboratively on bandwidth allocation by reading to the hierarchical NIB. We also present an improved traffic engineering algorithm by considering bandwidth and delay simultaneously, to maximize the network utilization while respecting max-min fairness. Experiments on a 719-switches 5-domain network topology demonstrate that our proposal could drive the link utilization ratio to more than 85%.