A telemetry session can be initiated using:
In a dial-in mode, an MDT receiver dials in to the router, and subscribes dynamically to one or more sensor paths or subscriptions. The router acts as the server and the receiver is the client. The router streams telemetry data through the same session. The dial-in mode of subscriptions is dynamic. This dynamic subscription terminates when the receiver cancels the subscription or when the session terminates.
There are two methods to request sensor-paths in a dynamic subscription:
OpenConfig RPC model: The
subscribe RPCdefined in the model is used to specify sensor-paths and frequency. In this method, the subscription is not associated with an existing configured subscription. A subsequent
cancelRPC defined in the model removes an existing dynamic subscription.
Cisco IOS XR supports Google network management interface (gNMI) protocol. gNMI is a unified mangement protocol for streaming telemetry data using gRPC framework. This framework and protocol do not need explicit configuration, but simplifies telemetry configuration on the router by starting only the gRPC server.
The RPC is defined in the gNMI proto file https://github.com/openconfig/gnmi/blob/master/proto/gnmi/gnmi.proto. The gNMI specification is published at https://github.com/openconfig/reference/blob/gnmi-0.3.1/rpc/gnmi/gnmi-specification.md.
IOS XR MDT RPC: IOS XR defines RPCs to subscribe and to cancel one or more configured subscriptions. The sensor-paths and frequency are part of the telemetry configuration on the router. A subscription is identified by its configured subscription name in the RPCs.
In a dial-out mode, the router dials out to the receiver. This is the default mode of operation. The router acts as a client and receiver acts as a server. In this mode, sensor-paths and destinations are configured and bound together into one or more subscriptions. The router continually attempts to establish a session with each destination in the subscription, and streams data to the receiver. The dial-out mode of subscriptions is persistent. When a session terminates, the router continually attempts to re-establish a new session with the receiver every 30 seconds.