I've finally finished my writeup describing the experiments that we performed using Openstack to drive a wide area 100 gigabit network. I've included all of the details for configuration and tuning, as well as speculation why we're seeing such good numbers. tl;dr: you can push a whole lot of network bandwidth out of an openstack deployment with kvm/virtio; we hit 98 gigabits peak with 10 instances across 50 ms of latency. The post is here: http://buriedlede.blogspot.com/2012/11/driving-100-gigabit-network-with.html I'm happy to discuss this in more detail, if there are additional questions. -nld