ON_CHANGE sensor support through gRPC Network Management Interface (gNMI) for Junos Telemetry Interface

ON_CHANGE streaming of Address Resolution Protocol (ARP), Network Discovery Protocol (NDP), and IP sensor information associated with interfaces is supported on Junos Telemetry Interface (JTI).

Periodical streaming of OpenConfig operational states and counters has been supported since Junos OS Release 16.1, exporting telemetry data from Juniper equipment to an external collector. While useful in collecting all the needed information and creating a baseline "snapshot," periodical streaming is less useful for time-critical missions. In such instances, you can configure ON_CHANGE streaming for an external collector to receive information only when operational states experience a change in state.

To support ON_CHANGE streaming, Google has developed a new specification called gRPC Network Management Interface (gNMI) for the modification and retrieval of configurations from a network element. Additionally, the gNMI specification can be used to generate and control telemetry streams from a network element to a data collection system. Using the new gNMI specification, one gRPC service definition can provide a single implementation on a network element for both configuration and telemetry as well as a single NMS element to interact with a device by means of telemetry and configuration RPCs.

Information about the RPCs supporting this feature can be found in the gNMI Proto file version 0.4.0 (the supported version) and the specification released by Google at:

• https://github.com/openconfig/reference/blob/primary/rpc/gnmi/gnmi-specification.md
• https://github.com/openconfig/gnmi/blob/primary/proto/gnmi/gnmi.proto

The telemetry RPC subscribe under gNMI service supports ON_CHANGE streaming. RPC subscribe allows a client to request the target to send it values of particular paths within the data tree. Values may be streamed (STREAM), sent one-off on a long-lived channel (POLL), or sent one-off as a retrieval (ONCE).

If a subscription is made for a top level container with a sample frequency of 0, leaves with ON_CHANGE support are streamed based on events. Other leaves will not be streamed.