Today, Romana, OpenShift, OpenContrail and Calico support network policies applied to namespaces and pods. Cisco and VMware are working on implementations as well. Both Romana and Calico demonstrated these capabilities with Kubernetes 1.2 recently at KubeCon. You can watch their presentations here: [Romana](https://www.youtube.com/watch?v=f-dLKtK6qCs) ([slides](http://www.slideshare.net/RomanaProject/kubecon-london-2016-ronana-cloud-native-sdn)), [Calico](https://www.youtube.com/watch?v=p1zfh4N4SX0) ([slides](http://www.slideshare.net/kubecon/kubecon-eu-2016-secure-cloudnative-networking-with-project-calico)).
**How does it work?**
Each solution has their their own specific implementation details. Today, they rely on some kind of on-host enforcement mechanism, but future implementations could also be built that apply policy on a hypervisor, or even directly by the network itself.
External policy control software (specifics vary across implementations) will watch the new API endpoint for pods being created and/or new policies being applied. When an event occurs that requires policy configuration, the listener will recognize the change and a controller will respond by configuring the interface and applying the policy. The diagram below shows an API listener and policy controller responding to updates by applying a network policy locally via a host agent. The network interface on the pods is configured by a CNI plugin on the host (not shown).
