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Module yang.ncdiff was initially developed internally in Cisco and is now available to the general public through open-source. It is integrated into the modular architecture of pyATS framework.

Docs: https://yangncdiff.readthedocs.io/en/latest/

GitHub: https://github.com/CiscoTestAutomation/yang.git

Introduction

Configuration is a major goal of NetConf. RFC 6241 claims "NETCONF defined in this document provides mechanisms to install, manipulate, and delete the configuration of network devices."

Each YANG model tries to abstract one aspect of configuration by a hierarchical schema. There might be a model to describe OSPF configuration, and another model to describe BGP configuration, etc.

For one model, there are many different possible configurations. Each configuration might be considered as a state, and it can be obtained by a get-config request. Between two states, there are two directional transitions: from state A to state B, and from state B to state A. Each transition corresponds to an edit-config RPC.

Primarily, there are three classes defined in this module: ModelDevice, Config and ConfigDelta.

  • A modeled device supporting multiple models - ModelDevice
  • A config state of multiple models - Config
  • A config delta between two configs - ConfigDelta

Quick examples can be found in section Tutorial.

Features

  • Connect to a Netconf device by an instance of ModelDevice
  • Download, compile and print model schemas
  • Get config states
  • Calculate diff of two instances of Config, so edit-config can be sent to the device to toggle between config state A and B
  • Given a config state and an edit-config, calculate the new config state
  • Support XPATH on Config and RPCReply
  • Instantiate Config objects by Netconf rpc-reply, Restconf GET reply or gNMI GetResponse
  • Present ConfigDelta objects in the form of Netconf (a config content of edit-config), Restconf (a list of Restconf Requests), or gNMI (a gNMI SetRequest).

Config Operations

Summary of config operations:

operand operator operand equality result note
Config + Config = Config Combine two config
Config + ConfigDelta = Config Apply edit-config to a config
ConfigDelta + ConfigDelta = N/A Not implemented
ConfigDelta + Config = Config Apply edit-config to a config
Config - Config = ConfigDelta Generate an edit-config
Config - ConfigDelta = Config Apply an opposite edit-config
ConfigDelta - ConfigDelta = N/A Not implemented
ConfigDelta - Config = N/A Not implemented

Support Mailers

Users are encouraged to contribute to yang.ncdiff module as expertise of data model testing grows in Cisco. Any questions or requests may be sent to [email protected].

Usage Examples

.. toctree::

   usage_tutorial
   usage_rc_put
   usage_rc_get
   usage_gnmi_set
   usage_gnmi_get
   usage_config
   usage_configdelta
   usage_model
   usage_running
   usage_rpcreply

Installation

yang.ncdiff module requires a few packages. Some of them are required implicitly:

Others are required directly:

Installation of these packages are normally smooth. Based on our support experience, most issues are related to lxml and paramiko.

This package can be installed from pypi server.

First-time installation:

pip install yang.ncdiff

To upgrade to the latest:

pip install --upgrade yang.ncdiff

.. sectionauthor:: Jonathan Yang <[email protected]>