Both JTI and gNMI have a number of RPCs specified. In the current version of Subscribe is supported for gNMI and telemetrySubscribe is supported for JTI.
The Streaming Telemetry agent accepts requests without the user or password set, since a router may or may not require user or password. If these fields are not present for JTI, the LoginCheck RPC is not called. This means that the router decides, so if, for example, user and password are not set and the router requires simple authentication, subsequent subscriptions will fail. For gNMI, the user and password, if present, are inserted in the meta data of the Subscribe RPC.