The YANG 1.1 Data Modeling Language
RFC 7950

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Internet Engineering Task Force (IETF)                 M. Bjorklund, Ed.
Request for Comments: 7950                                Tail-f Systems
Category: Standards Track                                    August 2016
ISSN: 2070-1721

                  The YANG 1.1 Data Modeling Language

Abstract

   YANG is a data modeling language used to model configuration data,
   state data, Remote Procedure Calls, and notifications for network
   management protocols.  This document describes the syntax and
   semantics of version 1.1 of the YANG language.  YANG version 1.1 is a
   maintenance release of the YANG language, addressing ambiguities and
   defects in the original specification.  There are a small number of
   backward incompatibilities from YANG version 1.  This document also
   specifies the YANG mappings to the Network Configuration Protocol
   (NETCONF).

Status of This Memo

   This is an Internet Standards Track document.

   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.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7950.

Bjorklund                    Standards Track                    [Page 1]
RFC 7950                        YANG 1.1                     August 2016

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
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   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
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   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Bjorklund                    Standards Track                    [Page 2]
RFC 7950                        YANG 1.1                     August 2016

Table of Contents

   1. Introduction ....................................................9
      1.1. Summary of Changes from RFC 6020 ..........................10
   2. Key Words ......................................................12
   3. Terminology ....................................................12
      3.1. A Note on Examples ........................................16
   4. YANG Overview ..................................................16
      4.1. Functional Overview .......................................16
      4.2. Language Overview .........................................18
           4.2.1. Modules and Submodules .............................18
           4.2.2. Data Modeling Basics ...............................19
           4.2.3. Configuration and State Data .......................23
           4.2.4. Built-In Types .....................................24
           4.2.5. Derived Types (typedef) ............................25
           4.2.6. Reusable Node Groups (grouping) ....................25
           4.2.7. Choices ............................................27
           4.2.8. Extending Data Models (augment) ....................28
           4.2.9. Operation Definitions ..............................29
           4.2.10. Notification Definitions ..........................31
   5. Language Concepts ..............................................32
      5.1. Modules and Submodules ....................................32
           5.1.1. Import and Include by Revision .....................33
           5.1.2. Module Hierarchies .................................34
      5.2. File Layout ...............................................36
      5.3. XML Namespaces ............................................36
           5.3.1. YANG XML Namespace .................................36