YANG Instance Data Files and their use for Documenting Server Capabilities

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Last updated 2018-02-07
Replaced by draft-ietf-netmod-yang-instance-file-format
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Network Working Group                                         B. Lengyel
Internet-Draft                                                  Ericsson
Intended status: Standards Track                               B. Claise
Expires: August 10, 2018                             Cisco Systems, Inc.
                                                        February 6, 2018

     YANG Instance Data Files and their use for Documenting Server


   This document specifies a standard file format for YANG instance
   data, that is data that could be stored in a datastore and whose
   syntax and semantics is defined by YANG models.  Instance data files
   can be used to provide information that is defined in design time.
   There is a need to document Server capabilities (which are often
   specified in design time), which should be done using instance data

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1.  Terminology

   Instance Data Set: A named set of data items that can be used as
   instance data in a YANG data tree.

   Instance Data File: A file containing an instance data set formatted
   according to the rules described in this document.

2.  Introduction

   A YANG server has a number of server-capabilities that can be
   retrieved from the server using protocols like NETCONF or RESTCONF.
   YANG server capabilities include among other things

   o  data defined in ietf-yang-library (YANG modules, submodules,
      features, deviations, schema-mounts)

   o  datastores supported

   o  alarms supported (draft-vallin-ccamp-alarm-module)

   o  data nodes, subtrees that support or do not support on-change
      notifications (draft-ietf-netconf-yang-push)-

   o  netconf-capabilities

   o  etc.

   While it is good practice to allow a client to query these
   capabilites from the live YANG server, that is often not enough.
   Many of these server-capabilities are relatively stable.  They may

   1.  only at upgrade, or

   2.  rarely (e.g. due to licensing), or

   3.  more frequently

   Most capabilities belong to type 1), some to type 2) and a relatively
   small set to type 3).  Many network nodes only have type 1) or type
   1+2) capabilities.  Stable capabilities are usually defined by a
   vendor in design time, before the product is released.  While these

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   capabilities can be retrieved from the live server in run-time, there
   is a strong need to provide the same data already during design time.
   (Often only a part of all the server capabilities can be made

   Often when a network node is released an associated NMS (network
   management system) is also released with it.  The NMS depends on the
   capabilities of the YANG server.  During NMS implementation the
   information about server capabilities is needed.  If the information
   is not available early in some off-line document, but only as
   instance data from the network node, the NMS implementation will be
   delayed, because it has to wait for the network node to be ready.
   Also assuming that all NMS implementors will have a correctly
   configured network node available to retrieve data from, is a very
   expensive proposition.  (An NMS may handle dozens of node types.)
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