optional string protocol = 3;

  // The application protocol for this port.
  // This is used as a hint for implementations to offer richer behavior for protocols that they understand.
  // This field follows standard Kubernetes label syntax.
  // Valid values are either:
  //
  // * Un-prefixed protocol names - reserved for IANA standard service names (as per
  // RFC-6335 and https://www.iana.org/assignments/service-names).