System-defined Configuration

3.1. Read-only to Clients

The <system> configuration datastore is a read-only configuration datastore (i.e., edits towards <system> directly MUST be denied), though the client may be allowed to override the value of a system-initialized data node (see Section 4.4). Configuration defined in <system> is merged into <intended>, and present in <operational> if it is actively in use by the device. Thus unless the resource is no longer available (e.g., the interface removed physically), there is no way to actually delete system configuration from a server, even if a client may be allowed to delete the configuration copied from <system> into <running>. Any deletable system-provided configuration must be defined in <factory-default> [RFC8808], which is used to initialize <running> when the device is first-time powered on or reset to its factory default condition.¶

3.2. May Change via Software Upgrades

System configuration MAY change dynamically, e.g., depending on factors like device upgrade or if system-controlled resources(e.g., HW available) change. In some implementations, when QoS function is enabled, QoS-related policies are created by system. If the system configuration gets changed, YANG notification (e.g., "push-change-update" notification) [RFC8641][RFC8639][RFC6470] can be used to notify the client. Any update of the contents in <system> will not cause the automatic update of <running>, even if some of the system configuration has already been copied into <running> explicitly or automatically before the update.¶

3.3. No Impact to <operational>

This work intends to have no impact to <operational>. As always, system configuration will appear in <operational> with "origin=system". This work enables a subset of those system generated nodes to be defined like configuration, i.e., made visible to clients in order for being referenced or configurable prior to present in <operational>. "Config false" nodes are out of scope, hence existing "config false" nodes are not impacted by this work.¶

4.1. Conceptual Model

This document introduces a mandatory datastore named "system" which is used to hold all three types of system configurations defined in Section 2.¶

When the device is powered on, immediately-active system configuration will be generated in <system> and applied immediately but inactive-until-referenced system configuration only becomes active if it is referenced by client-defined configuration. While conditionally-active system configuration will be created and immediately applied if the condition on system resources is met when the device is powered on or running.¶

All above three types of system configurations will appear in <system>. Clients MAY reference nodes defined in <system>, override values of configurations defined in <system>, and configure descendant nodes of system-defined nodes, by copying or writing intended configurations into the target configuration datastore (e.g., <running>).¶

The server will merge <running> and <system> to create <intended>, in which process, the data node appears in <running> takes precedence over the same node in <system> if the server allows the node to be modifiable; additional nodes to a list entry or new list/leaf-list entries appear in <running> extends the list entry or the whole list/leaf-list defined in <system> if the server allows the list/leaf-list to be updated. In addition, the <intended> configuration datastore represents the configuration after all configuration transformation to <system> are performed (e.g., system-defined template expansion, removal of inactive system configuration). If a server implements <intended>, <system> MUST be merged into <intended>.¶

Servers MUST enforce that configuration references in <running> are resolved within the <running> datastore and ensure that <running> contains any referenced system configuration. Clients MUST either explicitly copy system-defined nodes into <running> or use the "resolve-system" parameter. The server MUST enforce that the referenced system nodes configured into <running> by the client is consistent with <system>. Note that <system> aware clients know how to discover what nodes exist in <system>. How clients unaware of the <system> datastore can find appropriate configurations is beyond the scope of this document.¶

No matter how the referenced system configurations are copied into <running>, the nodes copied into <running> would always be returned after a read of <running>, regardless if the client is <system> aware.¶

4.2. Explicit Declaration of System Configuration

It is possible for a client to explicitly declare system configuration nodes in the target datastore (e.g., <running>) with the same values as in <system>, by configuring a node (list/leaf-list entry, leaf, etc) in the target datastore (e.g., <running>) that matches the same node and value in <system>.¶

This explicit configuration of system-defined nodes in <running> can be useful, for example, when the client doesn't want a "system client" to have a role or hasn't implemented the "resolve-system" parameter. The client can explicitly declare (i.e. configure in <running>) the list entries (with at least the keys) for any system configuration list entries that are referenced elsewhere in <running>. The client does not necessarily need to declare all the contents of the list entry (i.e. the descendant nodes) - only the parts that are required to make the <running> appear valid.¶

4.3. Servers Auto-configuring Referenced System Configuration

This document defines a new parameter "resolve-system" to the input for the <edit-config>, <edit-data> and <copy-config> operations. Clients that are aware of the "resolve-system" parameter MAY use this parameter to avoid the requirement to provide a referentially complete configuration in <running>.¶

If the "resolve-system" is present, the server MUST copy relevant referenced system-defined nodes into the target datastore (e.g., <running>) without the client doing the copy/paste explicitly, to resolve any references not resolved by the client. The server acting as a "system client" like any other remote clients copies the referenced system-defined nodes when triggered by the "resolve-system" parameter.¶

If the "resolve-system" parameter is not given by the client, the server should not modify <running> in any way otherwise not specified by the client. Not using capitalized "SHOULD NOT" in the previous sentence is intentional. The intention is bring awareness to the general need to not surprise clients with unexpected changes. It is desirable for clients to always opt into using mechanisms having server-side changes. This document enables a client to opt into this behavior using the "resolve-system" parameter. RFC 7317 enables a client to opt into its behavior using a "$0$" prefix (see ianach:crypt-hash type defined in [RFC7317]).¶

The server may automatically configure the list entries (with at least the keys) in the target datastore (e.g., <running>) for any system configuration list entries that are referenced elsewhere by the clients. Similarly, not all the contents of the list entry (i.e., the descendant nodes) are necessarily copied by the server - only the parts that are required to make the <running> valid. A read back of <running> (i.e., <get>, <get-config> or <get-data> operation) returns those automatically copied nodes.¶

4.5. Examples

This section shows the examples of server-configuring of <running> automatically, declaring a system-defined node in <running> explicitly, modifying a system-instantiated leaf's value and configuring descendant nodes of a system-defined node. For each example, the corresponding XML snippets are provided.¶

         module example-application {
           yang-version 1.1;
           namespace "urn:example:application";
           prefix "app";

           import ietf-inet-types {
             prefix "inet";
           }
           container applications {
             list application {
               key "name";
               leaf name {
                 type string;
               }
               leaf protocol {
                 type enumeration {
                   enum tcp;
                   enum udp;
                 }
               }
               leaf destination-port {
                 type inet:port-number;
               }
             }
           }
         }

        <applications xmlns="urn:example:application">
          <application>
            <name>ftp</name>
            <protocol>tcp</protocol>
            <destination-port>21</destination-port>
          </application>
          <application>
            <name>tftp</name>
            <protocol>udp</protocol>
            <destination-port>69</destination-port>
          </application>
          <application>
            <name>smtp</name>
            <protocol>tcp</protocol>
            <destination-port>25</destination-port>
          </application>
          ...
        </applications>

        <applications xmlns="urn:example:application">
          <application>
            <name>my-app-1</name>
            <protocol>tcp</protocol>
            <destination-port>2345</destination-port>
          </application>
          <application>
            <name>my-app-2</name>
            <protocol>udp</protocol>
            <destination-port>69</destination-port>
          </application>
        </applications>

         module example-acl {
           yang-version 1.1;
           namespace "urn:example:acl";
           prefix "acl";

           import example-application {
             prefix "app";
           }
           import ietf-inet-types {
             prefix "inet";
           }

           container acl {
             list acl_rule {
               key "name";
               leaf name {
                 type string;
               }
               container matches {
                 choice l3 {
                   container ipv4 {
                     leaf source_address {
                       type inet:ipv4-prefix;
                     }
                     leaf dest_address {
                       type inet:ipv4-prefix;
                     }
                   }
                 }
                 choice applications {
                   leaf-list application {
                     type leafref {
                     path "/app:applications/app:application/app:name";
                     }
                   }
                 }
               }
               leaf packet_action {
                 type enumeration {
                   enum forward;
                   enum drop;
                   enum redirect;
                 }
               }
             }
           }
         }

        <rpc message-id="101"
             xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
          <edit-config>
            <target>
              <running/>
            </target>
            <config>
              <acl xmlns="urn:example:acl">
                <acl_rule>
                  <name>allow_access_to_ftp_tftp</name>
                  <matches>
                    <ipv4>
                      <source_address>198.51.100.0/24</source_address>
                      <dest_address>192.0.2.0/24</dest_address>
                    </ipv4>
                    <application>ftp</application>
                    <application>tftp</application>
                    <application>my-app-1</application>
                  </matches>
                  <packet_action>forward</packet_action>
                </acl_rule>
              </acl>
            </config>
            <resolve-system/>
          </edit-config>
        </rpc>

        <applications xmlns="urn:example:application">
          <application>
            <name>my-app-1</name>
            <protocol>tcp</protocol>
            <destination-port>2345</destination-port>
          </application>
          <application>
            <name>my-app-2</name>
            <protocol>udp</protocol>
            <destination-port>69</destination-port>
          </application>
          <application>
            <name>ftp</name>
          </application>
          <application>
            <name>tftp</name>
          </application>
        </applications>

        <applications xmlns="urn:example:application"
                      xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
                      or:origin="or:intended">
          <application>
            <name>my-app-1</name>
            <protocol>tcp</protocol>
            <destination-port>2345</destination-port>
          </application>
          <application>
            <name>my-app-2</name>
            <protocol>udp</protocol>
            <destination-port>69</destination-port>
          </application>
          <application or:origin="or:system">
            <name>ftp</name>
            <protocol>tcp</protocol>
            <destination-port>21</destination-port>
          </application>
          <application or:origin="or:system">
            <name>tftp</name>
            <protocol>udp</protocol>
            <destination-port>69</destination-port>
          </application>
        </applications>

          <rpc message-id="101"
               xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
             <edit-config>
               <target>
                 <running/>
               </target>
               <config>
                 <applications xmlns="urn:example:application">
                   <application>
                     <name>ftp</name>
                   </application>
                   <application>
                     <name>tftp</name>
                   </application>
                 </applications>
               </config>
             </edit-config>
           </rpc>

        <rpc message-id="101"
             xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
          <edit-config>
            <target>
              <running/>
            </target>
            <config>
              <acl xmlns="urn:example:acl">
                <acl_rule>
                  <name>allow_access_to_ftp_tftp</name>
                  <matches>
                    <ipv4>
                      <source_address>198.51.100.0/24</source_address>
                      <dest_address>192.0.2.0/24</dest_address>
                    </ipv4>
                    <application>ftp</application>
                    <application>tftp</application>
                    <application>my-app-1</application>
                  </matches>
                  <packet_action>forward</packet_action>
                </acl_rule>
              </acl>
            </config>
          </edit-config>
        </rpc>

        <applications xmlns="urn:example:application">
          <application>
            <name>my-app-1</name>
            <protocol>tcp</protocol>
            <destination-port>2345</destination-port>
          </application>
          <application>
            <name>my-app-2</name>
            <protocol>udp</protocol>
            <destination-port>69</destination-port>
          </application>
          <application>
            <name>ftp</name>
          </application>
          <application>
            <name>tftp</name>
          </application>
        </applications>

        <applications xmlns="urn:example:application"
                      xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
                      or:origin="or:intended">
          <application>
            <name>my-app-1</name>
            <protocol>tcp</protocol>
            <destination-port>2345</destination-port>
          </application>
          <application>
            <name>my-app-2</name>
            <protocol>udp</protocol>
            <destination-port>69</destination-port>
          </application>
          <application>
            <name>ftp</name>
            <protocol or:origin="or:system">tcp</protocol>
            <destination-port or:origin="or:system">21</destination-port>
          </application>
          <application>
            <name>tftp</name>
            <protocol or:origin="or:system">udp</protocol>
            <destination-port or:origin="or:system">69</destination-port>
          </application>
        </applications>

       module example-qos-policy {
         yang-version 1.1;
         namespace "urn:example:qos";
         prefix "qos";

         container qos-policies {
            list policy {
              key "name";
              leaf name {
              type string;
            }
              list queue {
                key "queue-id";
                  leaf queue-id {
                    type int32 {
                      range "1..32";
                    }
                  }
                  leaf maximum-burst-size {
                    type int32 {
                      range "0..100";
                    }
                  }
                }
              }
            }
          }

        <qos-policies xmlns="urn:example:qos">
          <name>my-policy</name>
          <queue>
            <queue-id>1</queue-id>
            <maximum-burst-size>50</maximum-burst-size>
          </queue>
          <queue>
            <queue-id>2</queue-id>
            <maximum-burst-size>60</maximum-burst-size>
          </queue>
          <queue>
            <queue-id>3</queue-id>
            <maximum-burst-size>70</maximum-burst-size>
          </queue>
          <queue>
            <queue-id>4</queue-id>
            <maximum-burst-size>80</maximum-burst-size>
          </queue>
        </qos-policies>

        <rpc message-id="101"
             xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
          <edit-config>
            <target>
              <running/>
            </target>
            <config>
              <qos-policies xmlns="urn:example:qos">
                <name>my-policy</name>
                <queue>
                  <queue-id>1</queue-id>
                  <maximum-burst-size>55</maximum-burst-size>
                </queue>
              </qos-policies>
            </config>
          </edit-config>
        </rpc>

        <qos-policies  xmlns="urn:example:qos"
                       xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
                       or:origin="or:intended">
          <name>my-policy</name>
          <queue>
            <queue-id>1</queue-id>
            <maximum-burst-size>55</maximum-burst-size>
          </queue>
          <queue or:origin="or:system">
            <queue-id>2</queue-id>
            <maximum-burst-size>60</maximum-burst-size>
          </queue>
           <queue or:origin="or:system">
            <queue-id>3</queue-id>
            <maximum-burst-size>70</maximum-burst-size>
          </queue>
           <queue or:origin="or:system">
            <queue-id>4</queue-id>
            <maximum-burst-size>80</maximum-burst-size>
          </queue>
        </qos-policies>

      <interfaces>
        <interface>
          <name>lo0</name>
          <ip-address>127.0.0.1</ip-address>
          <ip-address>::1</ip-address>
        </interface>
      </interfaces>

     <interfaces xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
                 or:origin="or:system">
       <interface>
         <name>lo0</name>
         <ip-address>127.0.0.1</ip-address>
         <ip-address>::1</ip-address>
       </interface>
     </interfaces>

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <edit-config>
         <target>
           <running/>
         </target>
         <config>
           <interfaces>
             <interface>
               <name>lo0</name>
               <description>loopback</description>
             </interface>
           </interfaces>
         </config>
       </edit-config>
     </rpc>

        <interfaces xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
                    or:origin="or:intended">
          <interface>
            <name>lo0</name>
            <description>loopback</description>
            <ip-address or:origin="or:system">127.0.0.1</ip-address>
            <ip-address or:origin="or:system">::1</ip-address>
          </interface>
        </interfaces>

6.1. Data Model Overview

This YANG module defines a new YANG identity named "system" that uses the "ds:datastore" identity defined in [RFC8342]. A client can discover the <system> datastore support on the server by reading the YANG library information from the operational state datastore. Note that no new origin identity is defined in this document, the "or:system" origin Metadata Annotation [RFC7952] is used to indicate the origin of a data item is system. Support for the "origin" annotation is identified with the feature "origin" defined in [RFC8526].¶

The following diagram illustrates the relationship amongst the "identity" statements defined in the "ietf-system-datastore" and "ietf-datastores" YANG modules:¶

Identities:
    +--- datastore
    |  +--- conventional
    |  |  +--- running
    |  |  +--- candidate
    |  |  +--- startup
    |  |  +--- system
    |  |  +--- intended
    |  +--- dynamic
    |  +--- operational
 The diagram above uses syntax that is similar to but not defined in [RFC8340].

6.2. Example Usage

This section gives an example of data retrieval from <system>. The YANG module used are shown in Appendix C.2 of [RFC8342]. All the messages are presented in a protocol-independent manner. JSON is used only for its conciseness.¶

Suppose the following data is added to <running>:¶

{
    "bgp": {
        "local-as": "64501",
        "peer-as": "64502",
        "peer": {
            "name": "2001:db8::2:3"
        }
    }
}

REQUEST (a <get-data> or GET request sent from the NETCONF or RESTCONF client):¶

Datastore: <system>
Target:/bgp

An example of RESTCONF request:¶

      GET /restconf/ds/system/bgp HTTP/1.1
      Host: example.com
      Accept: application/yang-data+xml

RESPONSE ("local-port" leaf value is supplied by the system):¶

{
    "bgp": {
        "peer": {
            "name": "2001:db8::2:3",
            "local-port": "60794"
        }
    }
}

6.3. YANG Module

<CODE BEGINS> file="ietf-system-datastore@2022-08-09.yang"
 module ietf-system-datastore {
   yang-version 1.1;
   namespace "urn:ietf:params:xml:ns:yang:ietf-system-datastore";
   prefix sysds;

   import ietf-datastores {
     prefix ds;
     reference
       "RFC 8342: Network Management Datastore Architecture(NMDA)";
    }

    organization
      "IETF NETMDOD (Network Modeling) Working Group";

    contact
      "WG Web:   <http://tools.ietf.org/wg/netmod/>
       WG List:  <mailto:netmod@ietf.org>
       Author: Qiufang Ma
               <mailto:maqiufang1@huawei.com>
       Author: Kent Watsen
               <mailto:kent+ietf@watsen.net>
       Author: Qin Wu
               <mailto:bill.wu@huawei.com>
       Author: Chong Feng
               <mailto:frank.fengchong@huawei.com>
       Author: Jan Lindblad
               <mailto:jlindbla@cisco.com>";

    description
     "This module defines a new YANG identity that uses the
      ds:datastore identity defined in [RFC8342].

      Copyright (c) 2022 IETF Trust and the persons identified
      as authors of the code. All rights reserved.

      Redistribution and use in source and binary forms, with
      or without modification, is permitted pursuant to, and
      subject to the license terms contained in, the Revised
      BSD License set forth in Section 4.c of the IETF Trust's
      Legal Provisions Relating to IETF Documents
      (https://trustee.ietf.org/license-info).

      This version of this YANG module is part of RFC HHHH
      (https://www.rfc-editor.org/info/rfcHHHH); see the RFC
      itself for full legal notices.

      The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
      'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
      'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
      are to be interpreted as described in BCP 14 (RFC 2119)
      (RFC 8174) when, and only when, they appear in all
      capitals, as shown here.";

    revision 2022-08-09 {
      description

        "Initial version.";
      reference
       "RFC XXXX: System-defined Configuration";
    }

    identity system {
      base ds:conventional;
      description
        "This read-only datastore contains the complete configuration
         provided by the system itself.";
    }
}

<CODE ENDS>

7.1. Data Model Overview

This YANG module augments NETCONF <edit-config>, <edit-data> and <copy-config> operations with a new parameter "resolve-system" in the input parameters. If the "resolve-system" parameter is present, the server will copy the referenced system configuration into target datastore automatically. A NETCONF client can discover the "resolve-system" parameter support on the server by checking the YANG library information with "ietf-netconf-resolve-system" included from the operational state datastore.¶

The following tree diagram [RFC8340] illustrates the "ietf-netconf-resolve-system" module:¶

module: ietf-netconf-resolve-system
  augment /nc:edit-config/nc:input:
    +---w resolve-system?   empty
  augment /nc:copy-config/nc:input:
    +---w resolve-system?   empty
  augment /ncds:edit-data/ncds:input:
    +---w resolve-system?   empty

The following tree diagram [RFC8340] illustrates "edit-config", "copy-config" and "edit-data" rpcs defined in "ietf-netconf" and "ietf-netconf-nmda" respectively, augmented by "ietf-netconf-resolve-system" YANG module :¶

  rpcs:
    +---x edit-config
    |  +---w input
    |     +---w target
    |     |  +---w (config-target)
    |     |     +--:(candidate)
    |     |     |  +---w candidate?   empty {candidate}?
    |     |     +--:(running)
    |     |        +---w running?     empty {writable-running}?
    |     +---w default-operation?   enumeration
    |     +---w test-option?         enumeration {validate}?
    |     +---w error-option?        enumeration
    |     +---w (edit-content)
    |     |   +--:(config)
    |     |   |  +---w config?        <anyxml>
    |     |   +--:(url)
    |     |     +---w url?           inet:uri {url}?
    |     +---w resolve-system?      empty
    +---x copy-config
    |  +---w input
    |     +---w target
    |     |  +---w (config-target)
    |     |     +--:(candidate)
    |     |     |  +---w candidate?   empty {candidate}?
    |     |     +--:(running)
    |     |     |  +---w running?     empty {writable-running}?
    |     |     +--:(startup)
    |     |     |  +---w startup?     empty {startup}?
    |     |     +--:(url)
    |     |        +---w url?         inet:uri {url}?
    |     +---w source
    |     |  +---w (config-source)
    |     |     +--:(candidate)
    |     |     |  +---w candidate?   empty {candidate}?
    |     |     +--:(running)
    |     |     |  +---w running?     empty
    |     |     +--:(startup)
    |     |     |  +---w startup?     empty {startup}?
    |     |     +--:(url)
    |     |     |  +---w url?         inet:uri {url}?
    |     |     +--:(config)
    |     |        +---w config?      <anyxml>
    |     +---w resolve-system?       empty
    +---x edit-data
       +---w input
          +---w datastore            ds:datastore-ref
          +---w default-operation?   enumeration
          +---w (edit-content)
          |  +--:(config)
          |  |  +---w config?        <anydata>
          |  +--:(url)
          |     +---w url?           inet:uri {nc:url}?
          +---w resolve-system?      empty

7.2. Example Usage

This section gives an example of an <edit-config> request to reference system-defined data nodes which are not present in <running> with a "resolve-system" parameter. A retrieval of <running> to show the auto-copied referenced system configurations after the <edit-config> request is also given. The YANG module used is shown as follows, leafrefs refer to an existing name and address of an interface:¶

    module example-interface-management {
      yang-version 1.1;
      namespace "urn:example:interfacemgmt";
      prefix "inm";

      container interfaces {
        list interface {
          key name;
          leaf name {
            type string;
          }
          leaf description {
            type string;
          }
          leaf mtu {
            type uint16;
          }
          leaf ip-address {
            type inet:ip-address;
          }
        }
      }
      container default-address {
        leaf ifname {
          type leafref {
            path "../../interfaces/interface/name";
          }
        }
        leaf address {
          type leafref {
            path "../../interfaces/interface[name = current()/../ifname]"
               + "/ip-address";
          }
        }
      }
    }

Image that the system provides a loopback interface (named "lo0") with a predefined MTU value of "1500" and a predefined IP address of "127.0.0.1". The <system> datastore shows the following configuration of loopback interface:¶

<interfaces xmlns="urn:example:interfacemgmt">
  <interface>
    <name>lo0</name>
    <mtu>1500</mtu>
    <ip-address>127.0.0.1</ip-address>
  </interface>
</interfaces>

The client sends an <edit-config> operation to add the configuration of default-address with a "resolve-system" parameter:¶

<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="101">
  <edit-config>
    <target>
      <running/>
    </target>
    <config>
      <default-address xmlns="urn:example:interfacemgmt">
        <if-name>lo0</if-name>
        <address>127.0.0.1</address>
      </default-address>
    </config>
   <resolve-system/>
  </edit-config>
</rpc>

Since the "resolve-system" parameter is provided, the server will resolve any leafrefs to system configurations and copy the referenced system-defined nodes into <running> automatically with the same value (i.e., the name and ip-address data nodes of lo0 interface) in <system> at the end of <edit-config> operation constraint enforcement. After the processing, a positive resonse is returned:¶

<rpc-reply message-id="101"
     xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <ok/>
</rpc-reply>

Then the client sends a <get-config> operation towards <running>:¶

<rpc message-id="101"
     xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <get-config>
    <source>
      <running/>
    </source>
    <filter type="subtree">
      <interfaces xmlns="urn:example:interfacemgmt"/>
    </filter>
  </get-config>
</rpc>

Given that the referenced interface "name" and "ip-address" of lo0 are configured by the server, the following response is returned:¶

<rpc-reply message-id="101"
     xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <data>
    <interfaces xmlns="urn:example:interfacemgmt">
      <interface>
        <name>lo0</name>
        <ip-address>127.0.0.1</ip-address>
      </interface>
    </interfaces>
  </data>
</rpc-reply>

7.3. YANG Module

<CODE BEGINS> file="ietf-netconf-resolve-system@2022-08-09.yang"
 module ietf-netconf-resolve-system {
    yang-version 1.1;
    namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-resolve-system";
    prefix ncrs;

    import ietf-netconf {
      prefix nc;
      reference
        "RFC 6241: Network Configuration Protocol (NETCONF)";
    }

    import ietf-netconf-nmda {
      prefix ncds;
      reference
        "RFC 8526: NETCONF Extensions to Support the Network
         Management Datastore Architecture";
    }

    organization
      "IETF NETMOD (Network Modeling) Working Group";

    contact
      "WG Web:   <http://tools.ietf.org/wg/netmod/>
       WG List:  <mailto:netmod@ietf.org>
       Author: Qiufang Ma
               <mailto:maqiufang1@huawei.com>
       Author: Kent Watsen
               <mailto:kent+ietf@watsen.net>
       Author: Qin Wu
               <mailto:bill.wu@huawei.com>
       Author: Chong Feng
               <mailto:frank.fengchong@huawei.com>
       Author: Jan Lindblad
               <mailto:jlindbla@cisco.com>";

    description
      "This module defines an extension to the NETCONF protocol
       that allows the NETCONF client to control whether the server
       is allowed to copy referenced system configuration
       automatically without the client doing so explicitly.

        Copyright (c) 2022 IETF Trust and the persons identified
        as authors of the code. All rights reserved.

        Redistribution and use in source and binary forms, with
        or without modification, is permitted pursuant to, and
        subject to the license terms contained in, the Revised
        BSD License set forth in Section 4.c of the IETF Trust's
        Legal Provisions Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC HHHH
        (https://www.rfc-editor.org/info/rfcHHHH); see the RFC
        itself for full legal notices.

        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
        'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
        'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
        are to be interpreted as described in BCP 14 (RFC 2119)
        (RFC 8174) when, and only when, they appear in all
        capitals, as shown here.";

    revision 2022-08-09 {
      description
        "Initial version.";
      reference
        "RFC XXXX: System-defined Configuration";
    }

  augment /nc:edit-config/nc:input {
    description
      "Allows the server to automatically configure
       referenced system configuration to make configuration
       valid.";
     leaf resolve-system {
       type empty ;
       description
         "When present, the server is allowed to automatically
          configure referenced system configuration into the
          target configuration datastore.";
      }
   }

  augment /nc:copy-config/nc:input {
    description
      "Allows the server to automatically configure
       referenced system configuration to make configuration
       valid.";
     leaf resolve-system {
       type empty ;
       description
         "When present, the server is allowed to automatically
          configure referenced system configuration into the
          target configuration datastore.";
      }
   }

  augment /ncds:edit-data/ncds:input {
    description
      "Allows the server to automatically configure
       referenced system configuration to make configuration
       valid.";
     leaf resolve-system {
       type empty ;
       description
         "When present, the server is allowed to automatically
          configure referenced system configuration into the
          target configuration datastore.";
     }
   }
 }

<CODE ENDS>

Normative References

[RFC2119]

Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.

[RFC6241]

Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and A. Bierman, Ed., "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, <https://www.rfc-editor.org/info/rfc6241>.

[RFC7950]

Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, <https://www.rfc-editor.org/info/rfc7950>.

[RFC8342]

Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., and R. Wilton, "Network Management Datastore Architecture (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018, <https://www.rfc-editor.org/info/rfc8342>.

[RFC8526]

Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., and R. Wilton, "NETCONF Extensions to Support the Network Management Datastore Architecture", RFC 8526, DOI 10.17487/RFC8526, March 2019, <https://www.rfc-editor.org/info/rfc8526>.

Informative References

[I-D.ma-netmod-immutable-flag]

Ma, Q., Wu, Q., Lengyel, B., and H. Li, "YANG Extension and Metadata Annotation for Immutable Flag", Work in Progress, Internet-Draft, draft-ma-netmod-immutable-flag-02, July 2022, <https://www.ietf.org/archive/id/draft-ma-netmod-immutable-flag-02.txt>.

[RFC7317]

Bierman, A. and M. Bjorklund, "A YANG Data Model for System Management", RFC 7317, DOI 10.17487/RFC7317, August 2014, <https://www.rfc-editor.org/info/rfc7317>.

[RFC8174]

Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.

[RFC8407]

Bierman, A., "Guidelines for Authors and Reviewers of Documents Containing YANG Data Models", BCP 216, RFC 8407, DOI 10.17487/RFC8407, October 2018, <https://www.rfc-editor.org/info/rfc8407>.

[RFC8525]

Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K., and R. Wilton, "YANG Library", RFC 8525, DOI 10.17487/RFC8525, March 2019, <https://www.rfc-editor.org/info/rfc8525>.

[RFC8808]

Wu, Q., Lengyel, B., and Y. Niu, "A YANG Data Model for Factory Default Settings", RFC 8808, DOI 10.17487/RFC8808, August 2020, <https://www.rfc-editor.org/info/rfc8808>.

A.1. Device Powers On

<running>:¶

No configuration for "lo0" appears in <running>;

<system>:¶

     <interfaces>
       <interface>
         <name>lo0</name>
         <ip-address>127.0.0.1</ip-address>
         <ip-address>::1</ip-address>
       </interface>
     </interfaces>

<intended>:¶

     <interfaces>
       <interface>
         <name>lo0</name>
         <ip-address>127.0.0.1</ip-address>
         <ip-address>::1</ip-address>
       </interface>
     </interfaces>

<operational>:¶

     <interfaces xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
                 or:origin="or:system">
       <interface>
         <name>lo0</name>
         <ip-address>127.0.0.1</ip-address>
         <ip-address>::1</ip-address>
       </interface>
     </interfaces>

A.2. Client Commits Configuration

If a client creates an interface "et-0/0/0" but the interface does not physically exist at this point:¶

<running>:¶

     <interfaces>
       <interface>
         <name>et-0/0/0</name>
         <description>Test interface</description>
       </interface>
     </interfaces>

<system>:¶

     <interfaces>
       <interface>
         <name>lo0</name>
         <ip-address>127.0.0.1</ip-address>
         <ip-address>::1</ip-address>
       </interface>
     </interfaces>

<intended>:¶

     <interfaces>
         <name>lo0</name>
         <ip-address>127.0.0.1</ip-address>
         <ip-address>::1</ip-address>
       </interface>
       <interface>
         <name>et-0/0/0</name>
         <description>Test interface</description>
       </interface>
       <interface>
     </interfaces>

<operational>:¶

     <interfaces xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
                 or:origin="or:intended">
       <interface or:origin="or:system">
         <name>lo0</name>
         <ip-address>127.0.0.1</ip-address>
         <ip-address>::1</ip-address>
       </interface>
     </interfaces>

A.3. Operator Installs Card into a Chassis

<running>:¶

     <interfaces>
       <interface>
         <name>et-0/0/0</name>
         <description>Test interface</description>
       </interface>
     </interfaces>

<system>:¶

     <interfaces>
       <interface>
         <name>lo0</name>
         <ip-address>127.0.0.1</ip-address>
         <ip-address>::1</ip-address>
       </interface>
       <interface>
         <name>et-0/0/0</name>
         <mtu>1500</mtu>
       </interface>
     </interfaces>

<intended>:¶

     <interfaces>
         <name>lo0</name>
         <ip-address>127.0.0.1</ip-address>
         <ip-address>::1</ip-address>
       </interface>
       <interface>
         <name>et-0/0/0</name>
         <description>Test interface</description>
         <mtu>1500</mtu>
       </interface>
       <interface>
     </interfaces>

<operational>:¶

     <interfaces xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
                 or:origin="or:intended">
       <interface or:origin="or:system">
         <name or:origin>lo0</name>
         <ip-address>127.0.0.1</ip-address>
         <ip-address>::1</ip-address>
       </interface>
      <interface>
         <name>et-0/0/0</name>
         <description>Test interface</description>
         <mtu or:origin="or:system">1500</mtu>
       </interface>
       <interface>
     </interfaces>