Internet-Draft Groupings for QUIC clients and servers November 2024
Andersson Expires 13 May 2025 [Page]
Workgroup:
NETCONF Working Group
Internet-Draft:
draft-andersson-netconf-quic-client-server-02
Published:
Intended Status:
Standards Track
Expires:
Author:
P. Andersson
Cisco Systems

YANG Groupings for QUIC clients and QUIC servers

Abstract

This document defines three YANG 1.1 modules to support the configuration of QUIC clients and QUIC servers. The modules include basic parameters for configuring QUIC based clients and servers.

Editorial note (To be removed by the RFC Editor)

This draft contains placeholder values that need to be replaced with finalized values at the time of publication. This note summarizes all of the substitutions that are needed. No other RFC Editor instructions are specified elsewhere in this document.

Artwork in this document contains shorthand references to drafts in progress. Please apply the following replacements:

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on 13 May 2025.

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Table of Contents

1. Introduction

This documents defines two YANG 1.1 [RFC7950] modules to support the configuration of QUIC clients and QUIC servers (QUIC is defined in [RFC9000]), either as standalone or in conjunction with configuration of other protocol layers.

1.1. Terminology

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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

The following terms are defined in [RFC7950] and are not redefined here: client, data model, data tree, feature, extension, module, leaf, leaf-list, and server.

2. The "ietf-quic-common" Module

This section defines a YANG 1.1 module called "ietf-quic-common".

2.1. Data model overview

This section presents an overview of of the "ietf-quic-common" module in terms of features and groupings.

2.1.1. Groupings

The "ietf-quic-common" module defines the following "grouping" statement:

  • transport-parameters

This grouping is presented in the following subsection.

2.1.1.1. The "quic-common" Grouping

The following tree diagram [RFC8340] illustrates the "quic-common" grouping:

  grouping transport-parameters:
    +-- version?                        uint32
    +-- initial-rtt?                    uint32
    +-- congestion-control-algorithm?   string
    +-- max-idle-timeout?               uint32

Comments:

  • This grouping contains common transport parameters for QUIC connections.

2.2. YANG Module

<CODE BEGINS> file "[email protected]"

module ietf-quic-common{
  yang-version 1.1;
  namespace
    "urn:ietf:params:xml:ns:yang:ietf-quic-common";
  prefix quiccmn;

  organization
    "IETF NETCONF (Network Configuration) Working Group";

  contact
    "WG List: NETCONF WG list <mailto:[email protected]>
     WG Web:  https://datatracker.ietf.org/wg/netconf
     Author:  Per Andersson <mailto:[email protected]>";

  description
    "This module defines a reusable grouping that is common for
     QUIC clients and QUIC servers. This grouping statement is
     used by both 'ietf-quic-client' and 'ietf-quic-server'
     modules.

     Copyright (c) 2024 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 AAAA
     (https://www.rfc-editor.org/info/rfcAAAA); 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 2024-11-09 {
    description
      "Initial version";
    reference
      "RFC AAAA: YANG Groupings for QUIC Clients and QUIC Servers";
  }

  // Groupings

  grouping transport-parameters {
    description
      "A reusable grouping for QUIC Transport Parameters.";
    reference
      "RFC 9000: QUIC: A UDP-Based Multiplexed and Secure Transport
       RFC 9002: QUIC Loss Detection and Congestion Control
       RFC 9312: Manageability of the QUIC Transport Protocol";

    leaf version { type uint32; }
    leaf initial-rtt { type uint32; }
    leaf congestion-control-algorithm { type string; }
    leaf max-idle-timeout { type uint32; }
    leaf initial-max-streams-bidi { type uint32; }
    leaf initial-max-streams-uni { type uint32; }
    leaf keep-alive-interval { type uint32; }
  }
}

<CODE ENDS>

3. The "ietf-quic-client" Module

This section defines a YANG 1.1 module called "ietf-quic-client".

3.1. Data model overview

This section presents an overview of of the "ietf-quic-client" module in terms of features and groupings.

3.1.1. Features

The module itself does not define any features. However, in order to require TLS 1.3 the following "if-feature" is defined "tlscmn:tls13 not tlscmn:tls12". For QUIC TLS requirements see [RFC9001].

For further details about available features see the "ietf-tls-client" and "ietf-udp-client" modules. defined in [RFC9645] and [I-D.ietf-netconf-udp-client-server] respectively.

3.1.2. Groupings

The "ietf-quic-client" module defines the following "grouping" statement:

  • quic-client

This grouping is presented in the following subsection.

3.1.2.1. The "quic-client" Grouping

The following tree diagram [RFC8340] illustrates the "quic-client" grouping:

  grouping quic-client:
    +---u tlsc:tls-client-grouping
    |       {tlscmn:tls13 and not tlscmn:tls12}?
    +---u udpc:udp-client
    +---u quiccmn:transport-parameters

Comments:

  • This grouping uses the "tls-client-grouping" grouping discussed in [RFC9645]. Note that QUIC requires TLS 1.3 (or later), thus the "if-feature" invariant "tlscmn:tls13 and not tlscmn:tls12" is defined for this grouping.
  • This grouping uses the "udp-client-grouping" grouping discussed in [I-D.ietf-netconf-udp-client-server].

3.1.3. The "quic-client" Augments

The "ietf-quic-client" module augments the "/ncs:netconf-client/ncs:initiate" container [I-D.ietf-netconf-netconf-client-server] with the "if-feature" "quic-initiate".

This augment enables configuration of QUIC-level parameters for NETCONF client connections.

The following tree diagram [RFC8340] illustrates the "quic-client" augmentation of "netconf-client":

  augment /ncc:netconf-client/ncc:initiate:
  augment /ncc:netconf-client/ncc:initiate/ncc:netconf-server
            /ncc:endpoints/ncc:endpoint/ncc:transport:
    +--:(quic) {quic-initiate}?
       +--rw quic
          +---u quicc:quic-client

3.2. YANG Module

This YANG module has normative references to [RFC9645] and [I-D.ietf-netconf-udp-client-server].

<CODE BEGINS> file "[email protected]"

module ietf-quic-client {
  yang-version 1.1;
  namespace
    "urn:ietf:params:xml:ns:yang:ietf-quic-client";
  prefix quicc;

  import ietf-netconf-client {
    prefix ncc;
    reference
      "RFC HHHH: NETCONF Client and Server Models";
  }

  import ietf-quic-common {
    prefix quiccmn;
    reference
      "RFC AAAA: YANG Groupings for QUIC Clients and QUIC Servers";
  }

  import ietf-tls-client {
    prefix tlsc;
    reference
      "RFC 9645: YANG Groupings for TLS Clients and TLS Servers";
  }

  import ietf-tls-common {
    prefix tlscmn;
    reference
      "RFC 9645: YANG Groupings for TLS Clients and TLS Servers";
  }

  import ietf-udp-client {
    prefix udpc;
    reference
      "RFC CCCC: YANG Groupings for UDP Clients and UDP Servers";
  }

  organization
    "IETF NETCONF (Network Configuration) Working Group";

  contact
    "WG List: NETCONF WG list <mailto:[email protected]>
     WG Web:  https://datatracker.ietf.org/wg/netconf
     Author:  Per Andersson <mailto:[email protected]>";

  description
    "This module defines reusable groupings for QUIC clients that
     can be used as a basis for specific QUIC client instances.

     Copyright (c) 2024 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 AAAA
     (https://www.rfc-editor.org/info/rfcAAAA); 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 2024-11-09 {
    description
      "Initial version";
    reference
      "RFC AAAA: YANG Groupings for QUIC Clients and QUIC Servers";
  }

  // Features

  feature quic-initiate {
    description
      "The 'quic-initiate' feature indicates that the NETCONF client
       supports initiating QUIC connections to NETCONF servers.";
    reference
      "RFC AAAA: YANG Groupings for QUIC Clients and QUIC Servers";
  }

  /*
  FIXME
  feature quic-listen {
    description
      "The 'quic-listen' feature indicates that the NETCONF client
       supports opening a port to listen for incoming NETCONF
       server call-home QUIC connections.";
    reference
      "RFC 8071: NETCONF Call Home and RESTCONF Call Home";
    reference
      "RFC AAAA: YANG Groupings for QUIC Clients and QUIC Servers";
  }
  */

  // Groupings

  grouping quic-client {
    description
      "Grouping to configure a QUIC client.";
    reference
      "RFC 9000: QUIC: A UDP-Based Multiplexed and Secure Transport";

    uses tlsc:tls-client-grouping {
      if-feature "tlscmn:tls13 and not tlscmn:tls12";
      description
        "QUIC requires that TLS 1.3 (or later) is used.";
      reference
        "RFC 9001: Using TLS to Secure QUIC";
    }
    uses udpc:udp-client;
    uses quiccmn:transport-parameters;
  }

  // Augments

  /* FIXME seems pyang don't support this augment */
  augment "/ncc:netconf-client/ncc:initiate" {
    if-feature "quic-initiate";
    description
      "Add 'quic-initate' feature to the NETCONF client connection
       configuration.";
  }

  augment "/ncc:netconf-client/ncc:initiate/ncc:netconf-server" +
          "/ncc:endpoints/ncc:endpoint/ncc:transport" {
    description
      "Add QUIC transport to the NETCONF client connection
       configuration";
    case quic {
      if-feature "quic-initiate";
      container quic {
        description
          "QUIC-level client parameters to initiate a NETCONF over
           QUIC connection.";
        uses quicc:quic-client;
      }
    }
  }
}

<CODE ENDS>

4. The "ietf-quic-server" Module

This section defines a YANG 1.1 module called "ietf-quic-server".

4.1. Data model overview

This section presents an overview of of the "ietf-quic-server" module in terms of features and groupings.

4.1.1. Features

The module itself does not define any features. However, in order to require TLS 1.3 the following "if-feature" is defined "tlscmn:tls13 not tlscmn:tls12". For QUIC TLS requirements see [RFC9001].

For further details about available features see the "ietf-tls-server" and "ietf-udp-server" modules, defined in [RFC9645] and [I-D.ietf-netconf-udp-client-server] respectively.

4.1.2. Groupings

The "ietf-quic-server" module defines the following "grouping" statement:

  • quic-server

This grouping is presented in the following subsection.

4.1.2.1. The "quic-server" Grouping

The following tree diagram [RFC8340] illustrates the "quic-server" grouping:

  grouping quic-server:
    +---u tlss:tls-server-grouping
    |       {tlscmn:tls13 and not tlscmn:tls12}?
    +---u udps:udp-server
    +---u quiccmn:transport-parameters

Comments:

  • This grouping uses the "tls-server-grouping" grouping discussed in [RFC9645]. Note that QUIC requires TLS 1.3 (or later), thus the "if-feature" invariant "tlscmn:tls13 and not tlscmn:tls12" is defined for this grouping.
  • This grouping uses the "udp-server-grouping" grouping discussed in [I-D.ietf-netconf-udp-client-server].

4.1.3. The "quic-server" Augments

The "ietf-quic-server" module augments the "/ncs:netconf-server/ncs:listen" container [I-D.ietf-netconf-netconf-client-server] with the "if-feature" "quic-listen".

This augment enables configuration of QUIC-level parameters for NETCONF server connections.

The following tree diagram [RFC8340] illustrates the "quic-server" augmentation of "netconf-server":

  augment /ncs:netconf-server/ncs:listen:
  augment /ncs:netconf-server/ncs:listen/ncs:endpoints/ncs:endpoint
            /ncs:transport:
    +--:(quic) {quic-listen}?
       +--rw quic
          +---u quics:quic-server

4.2. YANG Module

This YANG module has normative references to [RFC9645] and [I-D.ietf-netconf-udp-client-server].

<CODE BEGINS> file "[email protected]"

module ietf-quic-server {
  yang-version 1.1;
  namespace
    "urn:ietf:params:xml:ns:yang:ietf-quic-server";
  prefix quics;

  import ietf-netconf-server {
    prefix ncs;
    reference
      "RFC HHHH: NETCONF Client and Server Models";
  }

  import ietf-quic-common {
    prefix quiccmn;
    reference
      "RFC AAAA: YANG Groupings for QUIC Clients and QUIC Servers";
  }

  import ietf-tls-server {
    prefix tlss;
    reference
      "RFC 9645: YANG Groupings for TLS Clients and TLS Servers";
  }

  import ietf-tls-common {
    prefix tlscmn;
    reference
      "RFC 9645: YANG Groupings for TLS Clients and TLS Servers";
  }

  import ietf-udp-server {
    prefix udps;
    reference
      "RFC CCCC: YANG Groupings for UDP Clients and UDP Servers";
  }

  organization
    "IETF NETCONF (Network Configuration) Working Group";

  contact
    "WG List: NETCONF WG list <mailto:[email protected]>
     WG Web:  https://datatracker.ietf.org/wg/netconf
     Author:  Per Andersson <mailto:[email protected]>";

  description
    "This module defines reusable groupings for QUIC servers that
     can be used as a basis for specific QUIC server instances.

     Copyright (c) 2024 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 AAAA
     (https://www.rfc-editor.org/info/rfcAAAA); 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 2024-11-09 {
    description
      "Initial version";
    reference
      "RFC AAAA: YANG Groupings for QUIC Clients and QUIC Servers";
  }

  // Features

  feature quic-listen {
    description
      "The 'quic-listen' feature indicates that the NETCONF server
       supports the QUIC transport.";
    reference
      "I-D.draft-ietf-netconf-over-quic-00: NETCONF over QUIC";
  }

  // FIXME feature quic-call-home

  // Groupings

  grouping quic-server {
    description
      "Grouping to configure a QUIC server.";
    reference
      "RFC 9000: QUIC: A UDP-Based Multiplexed and Secure Transport";

    uses tlss:tls-server-grouping {
      if-feature "tlscmn:tls13 and not tlscmn:tls12";
      description
        "QUIC requires that TLS 1.3 (or later) is used.";
      reference
        "RFC 9001: Using TLS to Secure QUIC";
    }
    uses udps:udp-server;
    uses quiccmn:transport-parameters;
  }

  // Augments

  /* FIXME seems pyang don't support this augment */
  augment "/ncs:netconf-server/ncs:listen" {
    if-feature "quic-listen";
    description
      "Add 'quic-listen' feature to the NETCONF server listen
       configuration.";
  }

  augment "/ncs:netconf-server/ncs:listen/ncs:endpoints" +
          "/ncs:endpoint/ncs:transport" {
    description
      "Add QUIC transport to the NETCONF server listen
       configuration.";
    case quic {
      if-feature "quic-listen";
      container quic {
        description
          "QUIC-level server parameters to listen for NETCONF over
           QUIC connections.";
        uses quics:quic-server;
      }
    }
  }
}

<CODE ENDS>

5. Security Considerations

This section follows the template defined in Section 3.7.1 of [RFC8407].

The YANG modules specified in this document defines a schema for data that is designed to be accessed via network management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC8446].

The Network Configuration Access Control Model (NACM) [RFC8341] provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content.

The modules presented in this draft does not contain any protocol accessible nodes, and thus the security considerations for such are not provided here.

Furthermore, the modules defines groupings, these considerations are primarily for the designers of other modules that use these groupings.

Security considerations for the groupings used in the modules are discussed in [RFC9645] and [I-D.ietf-netconf-udp-client-server], refer to these documents for further details.

Since the modules does not define any RPCs or actions or notifications, and thus the security considerations for such are not provided here.

6. IANA Considerations

6.1. The "IETF XML" Registry

This document registers three URIs in the "ns" subregistry of the IETF XML Registry [RFC3688] maintained at https://www.iana.org/assignments/xml-registry/xml-registry.xhtml#ns. Following the format in [RFC3688], the following registration is requested:

URI: urn:ietf:params:xml:ns:yang:ietf-quic-common
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.

URI: urn:ietf:params:xml:ns:yang:ietf-quic-client
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.

URI: urn:ietf:params:xml:ns:yang:ietf-quic-server
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.

6.2. The "YANG Module Names" Registry

This document registers three YANG modules in the YANG Module Names registry [RFC6020] maintained at https://www.iana.org/assignments/yang-parameters/yang-parameters.xhtml. Following the format defined in [RFC6020], the below registration is requested:

name: ietf-quic-common
namespace: urn:ietf:params:xml:ns:yang:ietf-quic-common
prefix: quiccmn
RFC: AAAA

name: ietf-quic-client
namespace: urn:ietf:params:xml:ns:yang:ietf-quic-client
prefix: quicc
RFC: AAAA

name: ietf-quic-server
namespace: urn:ietf:params:xml:ns:yang:ietf-quic-server
prefix: quics
RFC: AAAA

7. References

7.1. Normative References

[I-D.ietf-netconf-netconf-client-server]
Watsen, K., "NETCONF Client and Server Models", Work in Progress, Internet-Draft, draft-ietf-netconf-netconf-client-server-37, , <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-netconf-client-server-37>.
[I-D.ietf-netconf-udp-client-server]
Feng, A. H., Francois, P., and K. Watsen, "YANG Groupings for UDP Clients and UDP Servers", Work in Progress, Internet-Draft, draft-ietf-netconf-udp-client-server-05, , <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-udp-client-server-05>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC3688]
Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, , <https://www.rfc-editor.org/info/rfc3688>.
[RFC6241]
Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and A. Bierman, Ed., "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, , <https://www.rfc-editor.org/info/rfc6241>.
[RFC6242]
Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, , <https://www.rfc-editor.org/info/rfc6242>.
[RFC7950]
Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, , <https://www.rfc-editor.org/info/rfc7950>.
[RFC8040]
Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, , <https://www.rfc-editor.org/info/rfc8040>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/info/rfc8174>.
[RFC8341]
Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, , <https://www.rfc-editor.org/info/rfc8341>.
[RFC8407]
Bierman, A., "Guidelines for Authors and Reviewers of Documents Containing YANG Data Models", BCP 216, RFC 8407, DOI 10.17487/RFC8407, , <https://www.rfc-editor.org/info/rfc8407>.
[RFC8446]
Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, , <https://www.rfc-editor.org/info/rfc8446>.
[RFC9000]
Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Multiplexed and Secure Transport", RFC 9000, DOI 10.17487/RFC9000, , <https://www.rfc-editor.org/info/rfc9000>.
[RFC9001]
Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure QUIC", RFC 9001, DOI 10.17487/RFC9001, , <https://www.rfc-editor.org/info/rfc9001>.
[RFC9002]
Iyengar, J., Ed. and I. Swett, Ed., "QUIC Loss Detection and Congestion Control", RFC 9002, DOI 10.17487/RFC9002, , <https://www.rfc-editor.org/info/rfc9002>.
[RFC9312]
Kühlewind, M. and B. Trammell, "Manageability of the QUIC Transport Protocol", RFC 9312, DOI 10.17487/RFC9312, , <https://www.rfc-editor.org/info/rfc9312>.
[RFC9645]
Watsen, K., "YANG Groupings for TLS Clients and TLS Servers", RFC 9645, DOI 10.17487/RFC9645, , <https://www.rfc-editor.org/info/rfc9645>.

7.2. Informative References

[RFC6020]
Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, , <https://www.rfc-editor.org/info/rfc6020>.
[RFC8340]
Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, , <https://www.rfc-editor.org/info/rfc8340>.

Author's Address

Per Andersson
Cisco Systems