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Understanding Dial-Out Telemetry

Dial-out telemetry is a method used in network monitoring where the device (like a router) initiates the connection to send data to a collector. In dial-out telemetry, the device "dials out" to the collector, meaning it sends the initial SYN packet to establish the connection. This approach simplifies network management because it avoids the need to open ports for inbound management traffic.

Starting with Junos OS Release 22.4R1, JTI supports remote gRPC dial-out support on ACX Series routers, MX Series routers, PTX Series routers, and QFX Series switches. With gRPC dialout, the target device (server) initiates a gRPC session with the collector (client). When the session is established, the target streams the telemetry data that is specified by the sensor-group subscription to the collector. This is in contrast to the gRPC network management interface (gNMI) dial-in method, in which the collector initiates a connection to the target device.

gRPC dial-out simplifies streaming telemetry statistics. Configuring the target device to stream statistics and export them to a collector IP address removes the burden of access being placed on the collector (client).

Junos telemetry interface provides for the highly scalable streaming of telemetry information. Unlike previous monitoring systems, such as SNMP, which use the so-called pull model, the Junos telemetry interface uses the push model to collect data. The push model overcomes earlier scaling limits and reduces the processing required by the management station. You can enable monitoring and streaming of data for various system resources, such as physical and logical interfaces and firewall filters.

Figure 1: gRPC Dial-Out Diagram of a network telemetry process showing a Target Device connecting to a Collector via Customer Network. Step 1: DialOut to Configured Collectors. Step 2: Start Streaming Telemetry Data to all Connected Collectors. Arrows indicate data flow.

Benefits of Using Dial-Out Telemetry

  • Reduces target device exposure to threats outside of their topology.

  • Simplifies access to a target device. The gRPC Dial-In method requires a collector to overcome a series of complex firewall configurations to gain access to the target device. gRPC Dial-Out does not.

  • Collectors can be stateless; without the need to initiate a session, they simply listen, subscribe, and store collected data.

  • Support mutual encryption for heightened security.