  Software-defined networking (SDN) has improved the routing functionality in
networks like data centers or WANs. Recently, several studies proposed to apply
the SDN principles in the Internet's inter-domain routing as well. This could
offer new routing opportunities and improve the performance of BGP, which can
take minutes to converge to routing changes.
  Previous works have demonstrated that centralization can benefit the
functionality of BGP, and improve its slow convergence that causes severe
packet losses and performance degradation. However, due to (a) the fact that
previous works mainly focus on system design aspects, and (b) the lack of real
deployments, it is not clearly understood yet to what extent inter-domain SDN
can improve performance.
  To this end, in this work, we make the first effort towards analytically
studying the effects of routing centralization on the performance of
inter-domain routing, and, in particular, the convergence time of BGP.
Specifically, we propose a Markovian model for inter-domain networks, where a
subset of nodes (domains) coordinate to centralize their inter-domain routing.
We then derive analytic results that quantify the BGP convergence time under
various network settings (like, SDN penetration, topology, BGP configuration,
etc.). Our analysis and results facilitate the performance evaluation of
inter-domain SDN networks, which have been studied (till now) only through
simulations/emulations that are known to suffer from high time/resource
requirements and limited scalability.
