Letting remote Worker Node join local Kubernetes Cluster

What is the best way to add a remote worker node to a cluster set up in a data center?

“Remote”, as in a different network, somewhere else on the planet, relative to the data center’s location.

The current set up:

Data Center Remote
etcd worker

The communication between worker and master needs to work bidirectional, as if the worker node were actually in the data center.

I will gladly add additional information on request.