NetConf/YANG

What is NETCONF?

A network managing protocol to configure network elements.

It transports xml (json) via SSH.

<rpc-reply message-id="1" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <data>
    <interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces">
      <interface>
       <name>eth0</name>
       <type xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type">ianaift:ethernetCsmacd</type>
       <enabled>true</enabled>
       <ipv6 xmlns="urn:ietf:params:xml:ns:yang:ietf-ip">
         <address>
            <ip>2001:db8:c18:1::3</ip>
            <prefix-length>128</prefix-length>
          </address>
        </ipv6>
      </interface>
    </interfaces>
  </data>
</rpc-reply>

What is YANG?

A data modeling language for the definition of data sent over the NETCONF network configuration protocol. 
It is a schema to validate xml.

 container interfaces {
  description
    "Interface configuration parameters.";
  list interface {
    key "name";
    leaf name {
      type string;
    }
    leaf type {
      type identityref {
        base interface-type;
      }
      mandatory true;
    }
    leaf enabled {
      type boolean;
      default "true";
    }
  }  // list interface
}  // container interfaces

NETCONF Datastore concept

configuration datastore:

The datastore holding the complete set of configuration data that is required to get a device from its initial default state into a desired operational state.

running configuration datastore:

A configuration datastore holding the complete configuration currently active on the device. The running configuration datastore always exists.

candidate configuration datastore:

A configuration datastore that can be manipulated without impacting the device's current configuration and that can be committed to the running configuration datastore. Not all devices support a candidate configuration datastore.

startup configuration datastore:

The configuration datastore holding the configuration loaded by the device when it boots. Only present on devices that separate the startup configuration datastore from the running configuration datastore.

YANG

• YANG is a data modeling language for NETCONF (and RESTCONF) configuration and state data.
• It defines the syntax of the exchanged xml (and json) data between a NETCONF client (e.g. OpenDaylight) and a NETCONF server (a device)