System-defined Configuration

2.1. Immediately-Active

Immediately-active system configurations are those applied and active immediately (e.g., a loop-back interface) , irrespective of physical resource present or not, a special functionality enabled or not.¶

2.2. Conditionally-Active

System configurations which are provided and activated based on specific conditions being met in a system, e.g.,if a physical resource is present (e.g., insert interface card), the system will automatically detect it and load pre-provisioned configuration; when the physical resource is not present( remove interface card), the system configuration will be automatically cleared. Another example is when a special functionality is enabled, e.g., when QoS function is enabled, QoS policies are automatically created by the system.¶

2.3. Inactive-Until-Referenced

There are some predefined objects(e.g., application ids, anti-x signatures, trust anchor certs, etc) as a convenience for the clients. The clients can also define their own data objects for their unique requirements. Inactive-until-referenced system configurations are not applied and active immediately but only after they are referenced by client defined configuration.¶

3.1. Read-only to Clients

From the clients' perspective, the contents of the <system> datastore are read-only. There is no way to delete system configuration from a server. Any deletable system-provided configuration must be defined in <factory-default> [RFC 8808], 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 during device upgrade or system-controlled resources(e.g., HW available) . In some implementations, when QoS function is enabled, QoS-related predefined 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.¶

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 completely out of scope, hence existing "config false" nodes are not impacted by this work.¶

4.1. Conceptual Model

This document introduces an optional 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-activated system configuration will be provided and activated immediately but inactivated-until-referenced system configuration only becomes active if it is referenced by client defined configuration. While conditionally-activated system configuration will be created and immediately activated if the condition on system resources is met when the device is powered on or running.¶

All these system configuration will be implicitly hidden in the <running>, hence the client can retrieve them through standard operations defined in YANG-driven management protocols such as NETCONF and RESTCONF with a "with-system" query parameter. So that the client can get a merged view from the server.¶

If the <system> datastore exists, all above three types of system configurations will also go into <system>. Then the server will merge <running> and <system> to create <intended>, in which process, <running> MAY overwrite and/or extend <system>. If a server implements <intended>, <system> MUST be merged into <intended>.¶

When the client needs to configure the descendant nodes of system configuration(e.g., a physical interfaces), the ancestor system configuration needs to be configured in <running> explicitly.¶

4.2. Modifying (overriding) system configuration

In some cases, a server may allow some parts of system configuration to be modified. List keys in system configuration can't be changed by a client, but other descendant nodes in a list entry may be modifiable or non-modifiable. Leafs and leaf-lists outside of lists may also be modifiable or non-modifiable. Modification of system configuration is achieved by the client writing configuration to <running> that overrides the system configuration. Client configuration statements in <running> take precedence over system configuration nodes in <system> if the server allows the nodes to be modified. If a system configuration node is non-modifiable, then writing a value for that node in <running> returns an error.¶

A server may also allow a client to add data nodes to a list entry in <system> by writing those additional nodes in <running>. Those additional data nodes may not exist in <system> (i.e. an *addition* rather than an override).¶

While modifying (overriding) system configuration nodes may be supported by a server, there is no mechanism for deleting a system configuration node. A "mandatory true" leaf, for example, may have a value in <system> which can be modified (overridden) by a client setting that leaf to a value in <running>. But the leaf could not be deleted.¶

Comment 1: What if <System> contains a set of values for a leaf-list, and a client configures another set of values for that leaf-list in <running>, will the set of values in <running> completely replace the set of values in <system>? Or the two sets of values are merged together?¶

Comment 2: how "ordered-by user" lists and leaf-lists are merged? Do the <running> values go before or after, or is this a case where a full-replace is needed.¶

4.3. Explicit declaration of system configuration

In addition to modifying system configuration, and adding nodes to lists in system configuration as described above, a client can also explicitly declare system configuration nodes in <running> with the same values as in <system>. When a client configures a node (list entry, leaf, etc) in <running> that matches the same node & value in <system>, then that node becomes part of <running>. A read of <running> returns those explicitly configured nodes.¶

This explicit configuration of system configuration in <running> can be useful, for example, when an operator's workflow requires a client or offline tool to see the <running> configuration as valid. 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 offline.¶

4.4. Examples

The examples within this document use the fictional interface YANG module defined in Appendix C.3 of [RFC8342]. In addition, a fictional QoS data model example is provided.¶

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

        <qos-policies>
          <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>
                <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: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>

       <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>
                </interface>
              </interfaces>
            </config>
          </edit-config>
        </rpc>

        <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>
                </interface>
              </interfaces>
            </config>
          </edit-config>
        </rpc>

5.1. The "with-system" Query Parameter

As defined in Section 1.3 and Section 1.4, All the system configuration will be implicitly hidden in <running>, hence the client can retrieve them through standard operations defined in YANG-driven management protocols such as NETCONF and RESTCONF with a "with-system" parameter to get a merged view.¶

All servers MUST implement a "with-system" parameter.¶

5.2. The <system> Configuration Datastore

This section is not applicable to non-NMDA servers. NMDA servers SHOULD implement a <system> configuration datastore, and they SHOULD also implement the <intended> datastore, which can be used as an alternative to "with-system" parameter.¶

Following guidelines for defining datastores in the appendix A of [RFC8342], this document introduces a new optional datastore resource named 'system' that represents the system configuration. A device MAY implement the mechanism defined in this document without implementing the "system" datastore, which would only eliminate the ability to programmatically determine the system configuration.¶

• Name: "system"¶
• YANG modules: all¶
• YANG nodes: all "config true" data nodes¶
• Management operations: The content of the datastore is set by the server in an implementation dependent manner. The content can not be changed by management operations via NETCONF, RESTCONF,the CLI, etc, but may change itself by upgrades and/or when resource-conditions are met. The datastore can be read using the standard NETCONF/RESTCONF protocol operations.¶

• Origin: This document does not define any new origin identity when it interacts with <intended> datastore and finally flows into <operational>. The "system" origin Metadata Annotation [RFC7952] is used to indicate the origin of a data item.¶

  Comment: Should we define any new origin identity to indicate new source of system configuration datastore?¶

• Protocols: YANG-driven management protocols, such as NETCONF and RESTCONF.¶
• Defining YANG module: "ietf-system".¶

The datastore's content is populated by the server and read-only to clients. Upon the content is created or changed, it will be merged into <intended> datastore. Unlike <factory-default>[RFC8808], it MAY change dynamically, e.g., depending on factors like during device upgrade or system-controlled resources(e.g., HW available) and the <system> datastore does not have to persist across reboots. <factory-reset> RPC operation defined in [RFC8088] can reset it to its factory default configuration without including configuration generated due to the system update or client-enabled functionality.¶

6.1. Data Model Overview

This YANG module augments NETCONF <get> and <get-config> operation, which is designed to make implicitly hidden system configuration visible via a "with-system" parameter.¶

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

module: ietf-netconf-with-system
  augment /nc:get-config/nc:input:
    +---w with-system?   empty
  augment /nc:get/nc:input:
    +---w with-system?   empty

The following tree diagram [RFC8340] illustrates "get" and "get-config" rpcs defined in "ietf-netconf" augmented by "ietf-netconf-with-system" module :¶

  rpcs:
    +---x get-config
    |  +---w input
    |  |  +---w source
    |  |  |  +---w (config-source)
    |  |  |     +--:(candidate)
    |  |  |     |  +---w candidate?   empty {candidate}?
    |  |  |     +--:(running)
    |  |  |     |  +---w running?     empty
    |  |  |     +--:(startup)
    |  |  |        +---w startup?     empty {startup}?
    |  |  +---w filter?        <anyxml>
    |  |  +---w with-system?   empty
    |  +--ro output
    |     +--ro data?   <anyxml>
    +---x get
    |  +---w input
    |  |  +---w filter?        <anyxml>
    |  |  +---w with-system?   empty
    |  +--ro output
    |     +--ro data?   <anyxml>

6.2. Example Usage

This section gives an example of request/response pairs with and without the "with-system" query parameter. The YANG module used are shown in Appendix C.2 of [RFC8342].¶

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

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

All the messages are presented in a protocol-independent manner. JSON is used only for its conciseness.¶

REQUEST(without a "with-system" query parameter):¶

Target:/bgp
Query Parameter:
with-defaults: report-all

RESPONSE(both bgp/peer/local-as and bgp/peer/peer-as have default values for a peer. "local-port" leaf is not present in <running>):¶

{
    "bgp": {
        "local-as": "64501",
        "peer-as": "64502",
        "peer": {
            "name": "2001:db8::2:3",
            "local-as": "64501",
            "peer-as": "64502",
            "remote-port": "179",
            "state": "established"
        }
    }
}

REQUEST(with a "with-system" query parameter):¶

Target:/bgp
Query Parameter:
with-system
with-defaults: report-all

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

{
    "bgp": {
        "local-as": "64501",
        "peer-as": "64502",
        "peer": {
            "name": "2001:db8::2:3",
            "local-as": "64501",
            "peer-as": "64502",
            "local-port": "60794",
            "remote-port": "179",
            "state": "established"
        }
    }
}

6.3. YANG Module

<CODE BEGINS> file="ietf-netconf-with-system@2021-05-14.yang"
 module ietf-netconf-with-system {
    yang-version 1.1;
    namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-with-system";
    prefix ncws;

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

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

    contact
     "WG Web:   <http://tools.ietf.org/wg/netmod/>
      WG List:  <mailto:netmod@ietf.org>";
    description
     "This module defines an extension to the NETCONF protocol
      that allows the NETCONF client to control how system configuration
      data are handled by the server in particular NETCONF operations.

      Copyright (c) 2010 IETF Trust and the persons identified as
      the document authors.  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 Simplified BSD License
      set forth in Section 4.c of the IETF Trust's Legal Provisions
      Relating to IETF Documents
      (http://trustee.ietf.org/license-info).

      This version of this YANG module is part of RFC XXXX; see
      the RFC itself for full legal notices.";
    // RFC Ed.: replace XXXX with actual RFC number and remove this note

    revision 2021-05-14 {
      description
        "Initial version.";
      reference
       "RFC XXXX: System configuration Data handling Behavior";
    }

  augment /nc:get-config/nc:input {
     description " Allows the get-config operation to use
       with-system to retrieve the complete system configuration.";
     leaf with-system {
         type empty ;
         description
           "Support system configuration retrieval on
            conventional configuration datastore. ";
        }
   }

  augment /nc:get/nc:input {
     description " Allows the get operation to use
       with-system to retrieve the complete system configuration.";
     leaf with-system {
         type empty ;
         description
           "Support system configuration retrieval on
            running datastore.";
         }
   }
 }

<CODE ENDS>

7.1. Data Model Overview

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

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].

7.2. Example Usage

This section gives an example of data retrieval from <system>.¶

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

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

All the messages are presented in a protocol-independent manner. JSON is used only for its conciseness.¶

REQUEST:¶

Datastore: <system>
Target:/bgp

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

{
    "bgp": {
        "peer": {
            "local-port": "60794"
        }
    }
}

7.3. YANG Module

<CODE BEGINS> file="ietf-system-datastore@2021-05-14.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>";
    description
     "This module defines a new YANG identity that uses the
      ds:datastore identity defined in [RFC8342].

      Copyright (c) 2010 IETF Trust and the persons identified as
      the document authors.  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 Simplified BSD License
      set forth in Section 4.c of the IETF Trust's Legal Provisions
      Relating to IETF Documents
      (http://trustee.ietf.org/license-info).

      This version of this YANG module is part of RFC XXXX; see
      the RFC itself for full legal notices.";
    // RFC Ed.: replace XXXX with actual RFC number and remove this note

    revision 2021-05-14 {
      description

        "Initial version.";
      reference
       "RFC XXXX: System configuration Data handling Behavior";
    }

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

<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>.

Informative References

[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>.

[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>.

[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>.

[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>