YANG

YANG is a Data Modeling Language

Data Modeled

Config
State
RPCs (to make changes)
Notifications (to get events)

YANG was intended for NETCONF.

Functional Overview

YANG is a language used to model data for the NETCONF protocol. A YANG module defines a hierarchy of data that can be used for NETCONF- based operations, including configuration, state data, Remote Procedure Calls (RPCs), and notifications. This allows a complete description of all data sent between a NETCONF client and server.

Source RFC 6020 Section 4.1.

Terms

YANG — Yet Another Next Generation

Structured

Data that is formated for automation to use
Data that follows a schema

Schema

Rules around how data is allowed to be structured

Why

Device CLI output provides unstructured data

%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/9, changed state to down

YANG provides structured data which follows a schema

<config xmlns="http://tail-f.com/ns/config/1.0">
  <router xmlns="http://com/example/routermodel">
    <name>switch</name>
    <address>192.168.0.10</address>
    <operational-status>down</operational-status>
    <interface>
      <type>GigabitEthernet</type>
      <enabled>true</enabled>
      <interface-id>0/9</interface-id>
    </interface>
  </router>
</config>