RFC 9984

YANG Groupings for UDP Clients and UDP Servers

📅 published June 2026, from ietf

RFC 9984: YANG Groupings for UDP Clients and UDP Servers 🦋

Okay bestie, this one is from the IETF (Internet Engineering Task Force) and it's giving standards-track energy 💅 Here's the title-block tea:

  • Authors: A. Huang-Feng and P. Francois (both INSA-Lyon), plus K. Watsen (Watsen Networks) 🫶
  • Category: Standards Track 👑
  • Date: June 2026 📅
  • ISSN: 2070-1721 🌸
  • Obsoletes / Updates: nothing is listed in its header 🙈

Abstract ✨

Okay so this doc gives you two YANG 1.1 modules, and they come with reusable groupings for managing UDP clients and UDP servers 🎀

Status of This Memo 📜

This is an Internet Standards Track document, no cap 💖

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841 🦋

Info about the current status of this document, any errata, and how to give feedback on it lives at https://www.rfc-editor.org/info/rfc9984 ✨

Copyright (c) 2026 IETF Trust and the persons identified as the document authors. All rights reserved. 🌈

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, since they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License 📚

Table of Contents 🗂️

1.  Introduction
  1.1.  Requirements Language
  1.2.  Adherence to the NMDA
  1.3.  Conventions
2.  The "ietf-udp-client" Module
  2.1.  Data Model Overview
  2.2.  Example Usage
  2.3.  YANG Module
3.  The "ietf-udp-server" Module
  3.1.  Data Model Overview
  3.2.  Example Usage
  3.3.  YANG Module
4.  Security Considerations
5.  IANA Considerations
  5.1.  The "IETF XML Registry"
  5.2.  The "YANG Module Names" Registry
6.  References
  6.1.  Normative References
  6.2.  Informative References
Acknowledgements
Authors' Addresses

1. Introduction 🎀

This document presents two YANG 1.1 [RFC7950] modules with reusable groupings for managing UDP clients and UDP servers [RFC768]. These modules may be used directly (for example, to define a specific UDP client or UDP server) or alongside the configuration defined for higher-level protocols that depend on UDP 🌸

1.1. Requirements Language 💅

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. 🔥

1.2. Adherence to the NMDA 🧚

This document is compliant with the Network Management Datastore Architecture (NMDA) [RFC8342]. It does not define any protocol-accessible nodes that are "config false" 💜

1.3. Conventions 🍓

Various examples in this document use the XML [W3C.REC-xml-20081126] encoding. Other encodings, such as JSON [RFC8259], could alternatively be used ✨

2. The "ietf-udp-client" Module 🦋

This section defines a YANG 1.1 module called "ietf-udp-client". This YANG module defines the "udp-client" grouping for giving UDP clients information about their remote server 🫶

Section 2.1 gives the overview of the YANG module. An example of usage is in Section 2.2. Section 2.3 defines the YANG module itself 🌈

2.1. Data Model Overview 🌸

This section gives an overview of the features and the grouping defined in the "ietf-udp-client" YANG module 💖

2.1.1. Features 👑

The "ietf-udp-client" module defines the following "feature" statement:

Features:
  +-- local-binding

The diagram above uses syntax that is similar to the syntax used in [RFC8340]; but the syntax from the diagram is not defined in [RFC8340]. 🙈

This feature indicates that the client supports configuring local bindings (that is, the local address and local port number) for UDP clients ✨

2.1.2. The "udp-client" Grouping 🎀

The following tree diagram [RFC8340] shows the tree structure of the "udp-client" grouping:

module: ietf-udp-client

  grouping udp-client:
    +-- remote-address    inet:host
    +-- remote-port?      inet:port-number
    +-- local-address?    inet:ip-address {local-binding}?
    +-- local-port?       inet:port-number {local-binding}?

Here's the rundown on each parameter 💅

  • The "remote-address", which is mandatory, can be configured as an IPv4 address, an IPv6 address, or a hostname. The resolved address should be compatible with the local address family, if one is also provided. 🌍
  • The "remote-port" has neither a "default" nor a "mandatory" statement. YANG modules using this grouping SHOULD refine the grouping with a "default" statement when the port number is well-known (for example, a port number allocated by IANA), or with a "mandatory" statement if a port number always needs to be configured. This MAY be ignored when the port number is neither well-known nor mandatory to configure, which might be the case when this grouping is used by another grouping. 🧠
  • The "local-address", which is enabled by the "local-binding" feature, can be configured as an IPv4 address, an IPv6 address, or a wildcard value. In normal operation, the local and configured remote addresses SHOULD be from the same address family. Differences between address families may occur in abnormal or error conditions, so they are allowed to be reported. 🔥
  • The "local-port", which depends on the "local-binding" feature, is not mandatory. Its default value is "0", which tells the operating system it can pick an arbitrary port number 🦋

2.2. Example Usage 💖

This section shows an example of the "udp-client" grouping in action 🌸

<!-- The outermost element below doesn't exist in the data model. -->
<!--  It simulates if the "grouping" were a "container" instead.  -->

<udp-client xmlns="urn:ietf:params:xml:ns:yang:ietf-udp-client">
  <remote-address>www.example.com</remote-address>
  <remote-port>10000</remote-port>
  <local-address>192.0.2.2</local-address>
  <local-port>12345</local-port>
</udp-client>

2.3. YANG Module 👑

This module imports types defined in [RFC9911]. 🫶

<CODE BEGINS> file "ietf-udp-client@2026-06-15.yang"
module ietf-udp-client {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-udp-client";
  prefix udpc;

  import ietf-inet-types {
    prefix inet;
    reference
      "RFC 9911: Common YANG Data Types";
  }

  organization
    "IETF NETCONF (Network Configuration) Working Group";
  contact
    "WG Web:   <https://datatracker.ietf.org/group/netconf/>
     WG List:  <mailto:netconf@ietf.org>

     Authors:  Alex Huang Feng
               <mailto:alex.huang-feng@insa-lyon.fr>
               Pierre Francois
               <mailto:pierre.francois@insa-lyon.fr>";
  description
     "Defines a generic grouping for UDP-based client applications.

     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.

     Copyright (c) 2026 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).

     All revisions of IETF and IANA published modules can be found
     at the YANG Parameters registry group
     (https://www.iana.org/assignments/yang-parameters).

     This version of this YANG module is part of RFC 9984; see
     the RFC itself for full legal notices.";

  revision 2026-06-15 {
    description
      "Initial revision";
    reference
      "RFC 9984: YANG Groupings for UDP Clients and UDP Servers";
  }

  feature local-binding {
    description
      "Indicates that the UDP client supports configuring local
       bindings (i.e., the local address and local port number)
       for UDP clients.";
  }

  grouping udp-client {
    description
      "A reusable grouping for UDP clients.

       Note that this grouping uses fairly typical descendant
       node names such that a stack of 'uses' statements will
       have name conflicts.  It is intended that the consuming
       data model will resolve the issue (e.g., by wrapping
       the 'uses' statement in a container called
       'udp-client-parameters').  This module purposely does
       not do this itself so as to provide maximum flexibility
       to consuming models.";
    leaf remote-address {
      type inet:host;
      mandatory true;
      description
        "The IP address or hostname of the remote UDP server.";
    }
    leaf remote-port {
      type inet:port-number;
      description
        "The port number of the remote UDP server.";
    }
    leaf local-address {
      if-feature "local-binding";
      type inet:ip-address;
      description
        "The local IP address to bind to when sending UDP
         datagrams to the remote server. INADDR_ANY ('0.0.0.0') or
         INADDR6_ANY ('0:0:0:0:0:0:0:0' a.k.a. '::') may be used
         so that the client can bind to any IPv4 or IPv6 address.
         In normal operation, the local and configured
         remote addresses SHOULD be from the same address family.
         Differences between address families may occur in
         abnormal or error conditions; therefore, they are allowed to
         be reported.";
    }

    leaf local-port {
      if-feature "local-binding";
      type inet:port-number;
      default "0";
      description
        "The local port number to bind to when sending UDP
         datagrams to the remote server. The port number '0',
         which is the default value, indicates that any available
         local port number may be used.";
    }
  }
}
<CODE ENDS>

3. The "ietf-udp-server" Module 🧚

This section defines a YANG 1.1 module called "ietf-udp-server". This YANG module defines the "udp-server" grouping for managing UDP servers 💜

Section 3.1 gives an overview of the "ietf-udp-server" YANG module. An example of usage is in Section 3.2. Section 3.3 defines the YANG module itself 🍓

3.1. Data Model Overview ✨

This section gives an overview of the grouping defined in the "ietf-udp-server" module 🌈

3.1.1. The "udp-server" Grouping

okay so bestie, this is where the server grouping gets its whole personality 💅 the tree diagram [RFC8340] shows exactly how the "udp-server" grouping is laid out 🦋

   module: ietf-udp-server

     grouping udp-server:
       +-- local-bind* [local-address]
          +-- local-address    inet:ip-address
          +-- local-port?      inet:port-number

so here's the breakdown ✨

  • The "local-address" is mandatory 🫶 it can be an IPv4 address, an IPv6 address, or a wildcard value. no cap, it has to be one of those.
  • The "local-port" has neither a "default" nor a "mandatory" statement 🌸 that's the vibe. but yo, YANG modules that use this grouping SHOULD refine it with a "default" statement when the port number is well-known (like a port number IANA allocated) 🔥, or with a "mandatory" statement if a port number always needs to be configured 💜.
  • and this MAY be ignored when the port number is neither well-known nor mandatory to configure, like when this grouping gets used by another grouping 🙈 iykyk.

3.2. Example Usage

okay the examples are the cutest part 🎀 there are two of them, showing a server listening to an IPv4 address and then to IPv4 and IPv6 together 🧚

The following shows an example of a server configured for listening to an IPv4 address:

   <!-- The outermost element below doesn't exist in the data model. -->
   <!--  It simulates if the "grouping" were a "container" instead.  -->

   <udp-server xmlns="urn:ietf:params:xml:ns:yang:ietf-udp-server">
     <local-bind>
       <local-address>192.0.2.2</local-address>
       <local-port>49152</local-port>
     </local-bind>
   </udp-server>

The following shows an example of a server configured for listening to an IPv4 and IPv6 together:

   <!-- The outermost element below doesn't exist in the data model. -->
   <!--  It simulates if the "grouping" were a "container" instead.  -->

   <udp-server xmlns="urn:ietf:params:xml:ns:yang:ietf-udp-server">
     <local-bind>
       <local-address>192.0.2.2</local-address>
       <local-port>49152</local-port>
     </local-bind>
     <local-bind>
       <local-address>2001:db8::0</local-address>
       <local-port>49153</local-port>
     </local-bind>
   </udp-server>

3.3. YANG Module

this module imports types defined in [RFC9911] 🌈 here's the whole thing, copied exactly ✨

   <CODE BEGINS> file "ietf-udp-server@2026-06-15.yang"
   module ietf-udp-server {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-udp-server";
     prefix udps;

     import ietf-inet-types {
       prefix inet;
       reference
         "RFC 9911: Common YANG Data Types";
     }

     organization
       "IETF NETCONF (Network Configuration) Working Group";
     contact
       "WG Web:   <https://datatracker.ietf.org/group/netconf/>
        WG List:  <mailto:netconf@ietf.org>

        Authors:  Alex Huang Feng
                  <mailto:alex.huang-feng@insa-lyon.fr>
                  Pierre Francois
                  <mailto:pierre.francois@insa-lyon.fr>";
     description
       "Defines a generic grouping for UDP-based server applications.

        Copyright (c) 2026 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).

        All revisions of IETF and IANA published modules can be found
        at the YANG Parameters registry group
        (https://www.iana.org/assignments/yang-parameters).

        This version of this YANG module is part of RFC 9984; see
        the RFC itself for full legal notices.";

     revision 2026-06-15 {
       description
         "Initial revision";
       reference
         "RFC 9984: YANG Groupings for UDP Clients and UDP Servers";
     }

     grouping udp-server {
       description
         "A reusable grouping for managing UDP servers.

          Note that this grouping uses fairly typical descendant
          node names such that a stack of 'uses' statements will
          have name conflicts.  It is intended that the consuming
          data model will resolve the issue (e.g., by wrapping
          the 'uses' statement in a container called
          'udp-server-parameters').  This module purposely does
          not do this itself so as to provide maximum flexibility
          to consuming models.";
       list local-bind {
         key "local-address";
         min-elements 1;
         description
           "A list of bind (listen) points for this server
            instance.  A server instance may have multiple
            bind points to support, e.g., the same port number in
            different address families or different port numbers
            in the same address family.";
         leaf local-address {
           type inet:ip-address;
           mandatory true;
           description
             "The local IP address to listen on for incoming
              UDP datagrams.  INADDR_ANY ('0.0.0.0') or
              INADDR6_ANY ('0:0:0:0:0:0:0:0' a.k.a. '::') may be used
              so that the server can listen to any IPv4 or IPv6
              address.";
         }
         leaf local-port {
           type inet:port-number;
           description
             "The local port number to listen on for incoming UDP
              datagrams.";
         }
       }
     }
   }
   <CODE ENDS>
  1. Security Considerations ✨

this section uses the template described in Section 3.7.1 of [RFC9907] 💜

The "ietf-udp-client" and "ietf-udp-server" YANG modules define a data model that is designed to be accessed via YANG-based management protocols, such as the Network Configuration Protocol (NETCONF) [RFC6241] and RESTCONF [RFC8040]. These YANG-based management protocols (1) have to use a secure transport layer (e.g., Secure Shell (SSH) [RFC4252], TLS [RFC8446], and QUIC [RFC9000]) and (2) have to use mutual authentication. 😭🔥 mutual auth is NOT optional, bestie.

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. 🔐 basically NACM is the bouncer at the club 💅

These YANG modules define a set of identities, types, and groupings. These nodes are intended to be reused by other YANG modules. The modules by themselves do not expose any data nodes that are writable, data nodes that contain read-only state, or RPCs. As such, there are no additional security issues related to the YANG modules that need to be considered. 🦋

Modules that use the groupings that are defined in this document should identify the corresponding security considerations. For example, reusing some of these groupings will expose privacy-related information (e.g., 'remote-address', 'remote-port', 'local-address', or 'local-port'). 🙈 so if you reuse these groupings, go check your own security notes, bestie, because addresses and ports are private stuff.

  1. IANA Considerations 🌸

this document describes the URIs from the "IETF XML Registry" and the registration of two new YANG module names 🎀

5.1. The "IETF XML Registry"

IANA has assigned two new URIs from the "IETF XML Registry" [RFC3688]:

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

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

5.2. The "YANG Module Names" Registry

IANA has registered the following YANG modules in the "YANG Module Names" registry [RFC6020] within the "YANG Parameters" registry group:

   Name:  ietf-udp-client
   Maintained by IANA?  N
   Namespace:  urn:ietf:params:xml:ns:yang:ietf-udp-client
   Prefix:  udpc
   Reference:  RFC 9984

   Name:  ietf-udp-server
   Maintained by IANA?  N
   Namespace:  urn:ietf:params:xml:ns:yang:ietf-udp-server
   Prefix:  udps
   Reference:  RFC 9984
  1. References 📚

6.1. 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>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC768]   Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              DOI 10.17487/RFC0768, August 1980,
              <https://www.rfc-editor.org/info/rfc768>.

   [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>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [RFC9911]  Schönwälder, J., Ed., "Common YANG Data Types", RFC 9911,
              DOI 10.17487/RFC9911, December 2025,
              <https://www.rfc-editor.org/info/rfc9911>.

6.2. Informative References ✨

okay so these are the extra-reading picks 📚 the ones the doc points to for background, bestie 💅

Acknowledgements 🫶

the authors are literally so grateful to these people for their reviews and valuable comments 🥹 big thank yous to Mohamed Boucadair, Ran Chen, Benoit Claise, Mahesh Jethanandani, Qiufang Ma, Jürgen Schönwälder, Ketan Talaulikar, Éric Vyncke, Paul Wouters, and Qin Wu 💖 the reviewers really made this doc better, no cap ✨

Authors' Addresses 🦋

the squad behind this one, bestie 👑

Alex Huang Feng
INSA-Lyon
Lyon
France
Email: alex.huang-feng@insa-lyon.fr
Pierre Francois
INSA-Lyon
Lyon
France
Email: pierre.francois@insa-lyon.fr
Kent Watsen
Watsen Networks
Email: kent+ietf@watsen.net
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