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Integrated Global Navigation Satellite System (GNSS) on Routing Platforms

GNSS is a navigation aid system that uses signals from satellites to calculate the actual position of a GPS-capable receiver. These signals are not only used for determining the position of the receiver on Earth but also as a very accurate time base. Juniper provides routers that have the GNSS receiver integrated within the system. These routers support Telecom Grandmaster (T-GM) functionality.

Global Navigation Satellite System (GNSS) is a navigation aid system that uses signals from satellites to calculate the actual position of a GPS-capable receiver. These signals are not only used for determining the position of the receiver on Earth but also as a very accurate time base.

Juniper provides routers with the GNSS receiver integrated within the platform. This eliminates the need to have an external GPS receiver. Routers integrated with the GNSS receivers support the Telecom Grandmaster (T-GM) functionality. The T-GM acts as a G8275.1 T-GM (ordinary clock) by synchronizing itself to an internal/external GNSS receiver and drives time and frequency to the downstream PTP slaves via timestamps in PTP packets.

The inbuilt GPS receiver can be hooked to a GPS antenna to be able to receive GPS time. It then uses PTP to distribute this time to other network devices.​ The router enables GNSS input through SubMiniature version A (SMA) connector.

The ACX500, ACX7332, and ACX7348 routers support integrated GNSS receivers. Review the platform's hardware guide for more details.

Configuration

To enable T-GM feature you must configure the GNSS port and its associated parameters at the [edit chassis synchronization] hierarchy level. You must also configure the PTP settings under the [edit protocols ptp] hierarchy.

Configuring T-GM for ACX7332 and ACX7348 Routers

  1. Configure the GNSS settings under the [set chassis synchronization] hierarchy. You must specify at least one constellation option. A sample configuration snippet for mandatory GNSS configuration is provided below:

  2. Optionally, you can also configure the following GNSS options:

  3. Configure PTP T-GM configuration under the [set protocols ptp] hierarchy. A sample configuration snippet is provided below:

  4. Verify GNSS configuration:

  5. Verify PTP T-GM configuration:

Configuring T-GM for ACX500 Routers

  1. Configure the GNSS settings under the [set chassis synchronization] hierarchy. If you do not specify a constellation option, then the gps constellation option is considered by default. A sample configuration snippet is provided below:

  2. Configure PTP T-GM configuration under the [set protocols ptp] hierarchy. A sample configuration snippet is provided below:

  3. Verify the GNSS configuration:

  4. Verify the PTP T-GM configuration:

    Note:

    • The range for cable-length-compensation is from 0 to 50000000 nanoseconds.

    • The integrated GNSS receiver in the ACX500 series routers do not support 10-MHz frequency input and output.

    • PTP is not supported on 1G ports across all platforms. Refer PTP Features and Supported Platforms for information on PTP platforms and supported PTP features.