BKM: RTP Streaming under Kubernetes

RTP streaming (from an IP camera) requires to open multiple UDP ports. This presents challenge under Kubernetes, where a service must explicitly declare any open ports (one at a time as of v1.16.) To make things worse, if the container instance is replicated (say in a Deployment), each container instance must operate at different ranges of UDP ports to avoid port conflict on the same node.

Under Kubernetes, a UDP port can be defined in multiple ways:

HostPort

We can declare a UDP port directly at the POD level:

apiVersion: apps/v1
kind: Deployment
spec:
  replicas: 1
  template:
    spec:
      containers:
        - ports:
          - containerPort:
            protocol: UDP
            hostPort: 32546

NodePort

Instead of exposing port at the POD level, we can also declare the port at Service:

apiVersion: v1
kind: Service
spec:
  ports:
  - port: 32546
    protocol: UDP

There are drawbacks with the above approaches:

• Multiple Ports: As of Kubernetes v1.16, there is no support to declare a range of ports. With RTP, we need to open multiple UDP ports (each serving a video or audio stream.) We can workaround this issue utilizing m4 to generate the configuration:

apiVersion: v1
kind: Service
spec:
  ports:
forloop(`PORT',32546,32550,`dnl
  - port: defn(`PORT')
    protocol: UDP
    name: `udp'defn(`PORT')
')dnl

See Also: forloop

TODO