A comment rather than a question. Have you (Rancher) guys seen this recent analysis of network performance testing using native docker, Rancher overlay and Swarm (Impact of Docker and Rancher on Network Performance) ?
http://techtraits.com/dockerperf.html
Looks like the Rancher network agent fairs pretty well for TCP but dramatically less well for UDP ?
What would be your advice to those who want/need to use UDP ?