  The Internet is composed of Autonomous Systems (ASes) or domains, i.e.,
networks belonging to different administrative entities. Routing between
domains/ASes is realised in a distributed way, over the Border Gateway Protocol
(BGP). Despite its global adoption, BGP has several shortcomings, like slow
convergence after routing changes, which can cause packet losses and interrupt
communication even for several minutes. To accelerate convergence, inter-domain
routing centralization approaches, based on Software Defined Networking (SDN),
have been recently proposed. Initial studies show that these approaches can
significantly improve performance and routing control over BGP. In this paper,
we complement existing system-oriented works, by analytically studying the
gains of inter-domain SDN. We propose a probabilistic framework to analyse the
effects of centralization on the inter-domain routing performance. We derive
bounds for the time needed to establish data plane connectivity between ASes
after a routing change, as well as predictions for the control-plane
convergence time. Our results provide useful insights (e.g., related to the
penetration of SDN in the Internet) that can facilitate future research. We
discuss applications of our results, and demonstrate the gains through
simulations on the Internet AS-topology.
