Services in Kubernetes
Kubernetes Pods use IP networking to interact with other resources within a cluster. Pods are, however, fungible resources; they assume a new identity when termintated and replaced. Kubernetes provides no guarantees that a Pods IP address will remain static if a controller replaces it.
When a cluster state changes, it quickly becomes important to think about a service discovery layer that will facilitate communication between Pods in a cluster and connections from external resources.