  Modern Internet applications, from HD video-conferencing to health monitoring
and remote control of power-plants, pose stringent demands on network latency,
bandwidth and availability. An approach to support such applications and
provide inter-domain guarantees, enabling new avenues for innovation, is using
centralized inter-domain routing brokers. These entities centralize routing
control for mission-critical traffic across domains, working in parallel to
BGP. In this work, we propose using IXPs as natural points for stitching
inter-domain paths under the control of inter-domain routing brokers. To
evaluate the potential of this approach, we first map the global substrate of
inter-IXP pathlets that IXP members could offer, based on measurements for 229
IXPs worldwide. We show that using IXPs as stitching points has two useful
properties. Up to 91 % of the total IPv4 address space can be served by such
inter-domain routing brokers when working in concert with just a handful of
large IXPs and their associated ISP members. Second, path diversity on the
inter-IXP graph increases by up to 29 times, as compared to current BGP
valley-free routing. To exploit the rich path diversity, we introduce
algorithms that inter-domain routing brokers can use to embed paths, subject to
bandwidth and latency constraints. We show that our algorithms scale to the
sizes of the measured graphs and can serve diverse simulated path request
mixes. Our work highlights a novel direction for SDN innovation across domains,
based on logically centralized control and programmable IXP fabrics.
