YANG data models

Introduction

SR Linux supports a machine-readable description of OpenConfig YANG paths and the gNMI and gRPC operations that apply to each path. The description is delivered as a textual protobuf file called nosimage.textproto. You can use this file offline to design automation, validate client requests, and plan telemetry subscriptions without connecting to a router.

This topic describes how to obtain nosimage.textproto, how paths are represented, and how to read gNMI get, set, and subscribe capabilities, subscription modes, stream modes, and supported OpenConfig gRPC services.

About nosimage.textproto

nosimage.textproto is a human-readable instance of data defined by the nosimage.proto schema. The file references ocpaths.proto for OpenConfig path entries and ocrpcs.proto for supported gRPC services. Each release builds the file from the OpenConfig YANG models supported on SR Linux, including openconfig-srl-augments.yang and openconfig-srl-deviations.yang.

The file lists OpenConfig paths only. It does not describe Nokia native (srl_nokia) YANG. YANG action paths and action or RPC input and output containers are not included.

Platforms and delivery

Nokia provides a platform-specific nosimage.textproto file with the SR Linux software delivery for each supported chassis type. Per-platform files are available for the following platform variants.

• 7250 IXR-10e
• 7250 IXR-18e

Download the SR Linux release package for your platform from the Nokia software delivery portal and locate nosimage.textproto with the other release deliverables. Content can differ between platforms because supported OpenConfig paths depend on platform capabilities.

OpenConfig path format

Each path in nosimage.textproto is an absolute path from the OpenConfig data tree root. Paths are written without list key values. For example, a list may appear as /interfaces/interface/state/oper-status and not including a specific interface name.

The path list includes every supported OpenConfig node where gNMI get, set, or subscribe can apply. Container and list paths that support subscription are included when applicable.

gNMI capabilities per path

Path entries can include a gnmi_rpc block that indicates which gNMI RPCs are supported for that path. The following fields are used.

Subscription modes

When subscribe is true, nosimage.textproto lists one or more sub_mode values that describe how the target can deliver updates for that path, as defined in the gNMI specification:

• STREAM — the target streams values for the subscription.
• ONCE — the target sends values once and closes the subscription.
• POLL — the target sends updates when the client sends a poll request.

On SR Linux, Subscribe-capable paths typically list STREAM, ONCE, and POLL together.

Stream modes and sample interval

When sub_mode includes STREAM, stream_mode indicates how streamed updates are produced for that path. Values are derived from the telemetry-capability extension on the YANG node:

When stream_mode includes SAMPLE, sample_interval_nanoseconds gives the interval associated with sample=<n> in YANG. The extension uses seconds; nosimage.textproto stores nanoseconds (seconds × 10^9).

Supported gRPC services

The ocrpcs section of nosimage.textproto lists OpenConfig-related gRPC services, supported method names, and service version strings. Use this section together with per-path gnmi_rpc data when you implement client capability checks.

Example ocrpcs structure is as follows.

ocrpcs: {
  oc_protocols: {
    key: "gnmi"
    value: {
      method_name: "gnmi.gNMI.Get"
      method_name: "gnmi.gNMI.Set"
      method_name: "gnmi.gNMI.Subscribe"
      version: "0.10.0"
    }
  }
}

Method names use fully qualified gRPC identifiers (for example, gnoi.healthz.Healthz.Get).

Example path entry

The following example shows a path entry with gNMI capability and subscription information. Path and field values are illustrative.

ocpaths: {
  path: "/interfaces/interface/state/oper-status"
  gnmi_rpc: {
    get: true
    set: false
    subscribe: true
    sub_mode: STREAM
    sub_mode: ONCE
    sub_mode: POLL
    stream_mode: ON_CHANGE
  }
}

Using nosimage with management on the router

nosimage.textproto complements but does not replace on-device discovery and mapping artifacts.

• Enable OpenConfig with system management openconfig admin-state enable before using OpenConfig paths through gNMI.
• Set the gNMI origin to openconfig in request path prefixes, or configure system grpc-server yang-models openconfig on the gRPC server.
• Use the gNMI Capabilities RPC on a live device to learn gNMI service version, supported YANG models, and encodings. Capabilities does not provide per-path Subscribe or stream mode detail; use nosimage.textproto for that level of detail.
• After installation, OpenConfig-to-native path mappings remain in /opt/srlinux/mappings/openconfig as oc-srl.json files.