Dragon: Scalable, Flexible, and Efficient Traffic Engineering in Software Defined ISP Networks.

To optimize network cost, performance, and reliability, SDN advocates for centralized traffic engineering (TE) that enables more efficient path and egress point selection as well as bandwidth allocation. In this paper, we argue SDN-based TE for ISP networks can be very challenging. First, ISP networks often are very large in size, imposing significant scalability challenges to the centralized TE. Second, ISP networks usually have diverse types of links, switches, and cost models, leading to a complex combination of optimizations. Third, ISP networks not only have many choices of internal paths but also include rich selections of egress points and interdomain routes, unlike cloud/enterprise networks. To overcome these challenges, we present a novel TE application framework, called Dragon, for existing SDN control planes. To address the scalability challenge, Dragon consists of hierarchical and recursive TE algorithms and mechanisms that divide flow optimization problems into subtasks and execute them in parallel. Further, Dragon allows ISPs to express diverse objectives for different parts of their network. Finally, we extend Dragon to jointly optimize the selection of intradomain and interdomain paths. Using extensive evaluation on real topologies and prototyping with SDN controller and switches, we demonstrate that Dragon outperforms existing TE methods both in speed and optimality. [ABSTRACT FROM AUTHOR]