Regarding the yang model for netconf xml file

Question

Team I have the below xml file:

<?xml version="1.0" encoding="utf-8"?>
<rpc message-id="${TIMESTAMP}" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
    <get-config>
    <source>
    <running></running>
    </source>
    <filter>
    <interface-configurations xmlns="http://cisco.com/ns/yang/Cisco-IOS-XR-ifmgr-cfg"/>

    </filter>
    </get-config>
</rpc>

Q1: Will this netconf xml file have a yang model?

Q2: How can i access the underlying yang model(file) for this xml file?

score 4 · Accepted Answer · edited Oct 07 '21 at 08:57

Q1: Will this netconf xml file have a yang model?

You can easily determine if a device is using YANG to model its content from its <hello> message. Compliant devices advertise the YANG modules they support. The advertised capabilities will differ for YANG 1 and YANG 1.1.

For YANG 1 (RFC6020), this is what the specification says (5.6.4.1):

Servers indicate the names of supported modules via the <hello> message. Module namespaces are encoded as the base URI in the capability string, and the module name is encoded as the "module" parameter to the base URI.

A server MUST advertise all revisions of all modules it implements.

For example, this <hello> message advertises one module "syslog".

<hello xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
 <capability>
   http://example.com/syslog?module=syslog&amp;revision=2008-04-01
 </capability>
</hello>

For YANG 1.1 (RFC7950), in 5.6.4:

A NETCONF server MUST announce the modules it implements (see Section 5.6.5) by implementing the YANG module "ietf-yang-library" defined in [RFC7895] and listing all implemented modules in the "/modules-state/module" list.

The server also MUST advertise the following capability in the <hello> message (line breaks and whitespaces are used for formatting reasons only):

urn:ietf:params:netconf:capability:yang-library:1.0?

   revision=<date>&module-set-id=<id>

The parameter "revision" has the same value as the revision date of the "ietf-yang-library" module implemented by the server. This parameter MUST be present.

The parameter "module-set-id" has the same value as the leaf "/modules-state/module-set-id" from "ietf-yang-library". This parameter MUST be present.

With this mechanism, a client can cache the supported modules for a server and only update the cache if the "module-set-id" value in the <hello> message changes.

_{can't seem to find a way to stop the above blockquote, hence this}

Q2: How can i access the underlying yang model(file) for this xml file?

Device manufacturers usually provide a download page on their website, where you obtain their YANG files. Note that not all devices support YANG. NETCONF does not specify what content is modeled with; could be a bunch of XSD schemas, YANG, RelaxNG, etc., though YANG was designed with this purpose in mind (initially).

There is also an optional standard operation defined, called <get-schema>, which is part of ietf-netconf-monitoring YANG module. You first discover available schema, then obtain them. Since it is optional, not all devices support it.

<?xml version="1.0" encoding="utf-8"?>
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="2">
  <get>
    <filter type="subtree">
      <ncm:netconf-state xmlns:ncm="urn:ietf:params:xml:ns:yang:ietf-netconf-monitoring">
        <ncm:schemas/>
      </ncm:netconf-state>
    </filter>
  </get>
</rpc>

<?xml version="1.0" encoding="utf-8"?>
<rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="2">
  <data>
    <netconf-state xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-monitoring">
      <schemas>
        <schema>
          <identifier>ietf-inet-types</identifier>
          <version>2013-07-15</version>
          <format>yang</format>
          <namespace>urn:ietf:params:xml:ns:yang:ietf-inet-types</namespace>
          <location>NETCONF</location>
        </schema>
        <!-- ... -->
      </schemas>
    </netconf-state>
  </data>
</rpc-reply>

<?xml version="1.0" encoding="utf-8"?>
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="8">
  <get-schema xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-monitoring">
    <identifier>ietf-interfaces</identifier>
    <version>2014-05-08</version>
    <format>yang</format>
  </get-schema>
</rpc>

<?xml version="1.0" encoding="utf-8"?>
<rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="8">
  <data xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-monitoring">module ietf-interfaces {

  namespace "urn:ietf:params:xml:ns:yang:ietf-interfaces";
  prefix if;
  
  // ...
  }
  </data>
</rpc-reply>

Regarding the yang model for netconf xml file

1 Answers1