YangPush Notification Capabilities
draft-lengyel-netconf-notification-capabilities-00

Network Working Group                                         B. Lengyel
Internet-Draft                                                  Ericsson
Intended status: Standards Track                                A. Clemm
Expires: August 26, 2018                                      Huawei USA
                                                       February 22, 2018

                   YangPush Notification Capabilities
           draft-lengyel-netconf-notification-capabilities-00

Abstract

   This document proposes a YANG module that allows a YANG server to
   specify for which data nodes it will send "YANG Datastore
   Subscription" on-change notifications.  It also proposes to use YANG
   Instance Data to document this information in implementation time.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on August 26, 2018.

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   document authors.  All rights reserved.

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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.

   On-change Notification Capability: The capability of the YANG server
   to send on-change notifications on the change of the value for a
   specific data node.

   Implementation-time information: Information about the YANG server's
   behavior that is made available during the implementation of the
   server, available from a source other then a running Yang server .

   Rutime-information: Information about the YANG server's behavior that
   is available from the running YANG server via a protocol like
   NETCONF, RESTCONF or HTTPS.

2.  Introduction

   As defined in [I-D.ietf-netconf-yang-push] a YANG server may allow
   clients to subscribe to updates from a datastore and subsequently
   push such update notifications to the client.  Notifications may be
   sent periodically or on-change (more or less immendiately after each
   change).

   In some cases, a publisher supporting on-change notifications will
   not be able to push updates for some object types on-change.  Reasons
   for this might be that the value of the datastore node changes
   frequently (e.g. in-octets counter), that small object changes are
   frequent and meaningless (e.g., a temperature gauge changing 0.1
   degrees), or that the implementation is not capable of on-change
   notification for a particular object.  In those cases, it will be
   important for client applications to have a way to identify for which
   objects on-change notifications are supported and for which ones they
   are not supported.

   Faced with the reality that support for on-change notification does
   not mean that such notifications will be sent for any specific data
   node, client/management applications can not rely on the on-change
   functionality unless the client has some means to identify for which
   objects on-change notifications are supported and for which ones they
   are not supported.  YANG models are meant to be used as an interface
   contract.  Without identification of data nodes supporting on-change,
   today this contract only states the YANG server may (or may not) send
   on-change notifications for a data node specified in a YANG module.

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   This document proposes a YANG module that allows a client to identify
   which data nodes support on-change notification, removing the
   uncertainty for on-change notifications.

   On-change Notification Capability information will be needed both in
   implementation-time and run-time.

   Run-time information is needed

   o  for any "purely model driven" client

   o  to check that early information about the capability is indeed
      what the server supports

   o  in case the capability might change during run-time e.g. due to
      licensing, HW constraints etc.

   Implementation time information is needed by Network Management
   System (NMS) implementers.  During NMS implementation for any
   functionality that depends on the notifications the information about
   on change notification capability is needed.  If the information is
   not available early in some 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 implementers will have a correctly configured network node
   available to retrieve data from, is very expensive.  (An NMS may
   handle dozens of network node types.)  Often the NMS is a requirement
   for introducing a new network node type into a network, so delaying
   the NMS effectively delays the availability of the network node as
   well.

   Implementation time information is needed by system integrators.
   System integrators will need information about on change notification
   capability early.  When introducing a network node type into their
   network Network operators often need to integrate the node type into
   their own management system.  The NMS may have management functions
   that depend on on-change notifications.  The network operator needs
   to plan his management practices and NMS implementation before he
   even decides to buy the specific network node type.  Moreover the
   decision to buy the node type sometimes depends on these management
   possibilities.

3.  On-change Notification Capability Model

   As described above a number of stakeholders need information about
   the on change notification capability both in implementation and run-
   time.  It is a goal to provide this information in a format that is

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   o  vendor independent (standard)

   o  formal (no freeform English text please)

   o  the same both in implementation-time and run-time

   The YANG module ietf-notification-capabilities is defined to provide
   information about the on-change notification capabilities.  It is
   defined as an extension to the ietf-yang-library module
   [I-D.ietf-netconf-rfc7895bis].  For each YANG Module listed in the
   ietf-yang-library there is a default notification capability
   separately for config false and config true data nodes.  There is
   also an on-change-notification-capability list containing a
   potentially different true/false notification capability for any data
   nodes in the schema tree.  Unless a node is in the list with a
   specific capability value, it inherits its on-change-notification-
   capability from its parent in the data tree, or from the relevant
   default values.

   The instance information can be provided in one of two ways:

   o  It can be dynamically populated by a server during runtime.

   o  It can be provided by an implementer as YANG instance data
      (possibly retrievable through NETCONF or RESTCONF, but preferably
      also through other means including but not limited to download
      from product Websites) according to [I-D.lengyel-netmod-yang-
      instance-data]

   As the same information is also needed in implementation-time YANG
   servers SHOULD document their on-change-notification-capabilities
   using YANG Instance data according to
   [I-D.lengyel-netmod-yang-instance-data]  following the ietf-
   notification-capabilities module.

3.1.  Tree Diagram

   The following tree diagram [I-D.ietf-netmod-yang-tree-diagrams]
   provides an overview of the data model.

   module: ietf-notification-capabilities
     augment /yanglib:yang-library/yanglib:module-set:
       +--ro notification-sent-for-config-default?   boolean
       +--ro notification-sent-for-state-default?    boolean
       +--ro on-change-notification-capability* [data-node-selector]
       |  +--ro data-node-selector    nacm:node-instance-identifier
       +--ro on-change-notification-sent?            boolean

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3.2.  YANG Module

   <CODE BEGINS> file "ietf-notification-capabilities.yang"

   module ietf-notification-capabilities {
     yang-version 1.1;
     namespace
       "urn:ietf:params:xml:ns:yang:ietf-notification-capabilities";
     prefix inc;

     import ietf-yang-library {
       prefix yanglib;
       reference "rfc7895bis";
     }

     import ietf-netconf-acm { prefix nacm; }

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

     contact
       "WG Web:   <https://datatracker.ietf.org/wg/netconf/>
        WG List:  <mailto:netconf@ietf.org>

        WG Chair: Kent Watsen
                  <mailto:kwatsen@juniper.net>

        WG Chair: Mahesh Jethanandani
                  <mailto:mjethanandani@gmail.com>

        Editor:   Balazs Lengyel
                  <mailto:balazs.lengyel@ericsson.com>";

     description "This module augments the ietf-yang-library to
       specify per module for which data nodes will the YANG server
       send on-change notifications.

       On-change notification capability is marked as true or false.
       This marking is inherited from the parent down the data tree
       unless explicitly marked otherwise.

       On-change notifications SHALL be sent for a configuration
       data node if one of the following is true:
       - it is specified in the on-change-notification-capability
       list and has a on-change-notification-sent value true or
       - notifications are sent for its parent data node and it is
       not specified in the on-change-notification-capability list or

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       - if it is a top level data-node and is not specified in the
       on-change-notification-capability list and the
       notification-sent-for-config-default is true.

       For state data nodes the same rules appiy except for top
       level nodes the notification-sent-for-state-default value
       SHALL be considered.
       ";

     revision 2018-02-20 {
       description "Initial version";
       reference
         "RFC XXX: YangPush Notification Capabilities";
     }

     // if we base on the RFC7895 current version
     // augment /yanglib:modules-state/yanglib:modules/yanglib:module {

     // if we base on the RFC7895bis
     augment /yanglib:yang-library/yanglib:module-set {
       description "Extends the ietf-yang-library module with
           on-change-notification-capability information";

       leaf notification-sent-for-config-default {
         type boolean;
         default true;
         description "Specifies the default value for this module's
           top level configuration data nodes for the
           on-change-notification-sent capability.";
       }

       leaf notification-sent-for-state-default {
         type boolean;
         default false;
         description "Specifies the default value for this module's
           top level state data nodes for the
           on-change-notification-sent capability.";
       }

       list on-change-notification-capability {
         key data-node-selector ;
         description "A list of data nodes that have the
            on-change-notification-capability specifically defined.";

         leaf data-node-selector {
           type nacm:node-instance-identifier;
           description data-node-selector;
           }

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         }

         leaf on-change-notification-sent {
           type boolean;
           description "Specifies whether the YANG server will
             send on-change notifications for the selected data nodes.";
       }
     }
   }

   <CODE ENDS>

4.  Security Considerations

   The YANG module defined in this document is designed to be accessed
   via YANG based management protocols, such as NETCONF and RESTCONF.
   Both of these protocols have mandatory-to- implement secure transport
   layers (e.g., SSH, TLS) with mutual authentication.

   The NETCONF access control model (NACM) provides the means to
   restrict access for particular users to a pre-configured subset of
   all available protocol operations and content.

5.  IANA Considerations

5.1.  The IETF XML Registry

   This document registers one URI in the IETF XML registry [RFC3688].
   Following the format in [RFC3688], the following registrations are
   requested:

      URI: urn:ietf:params:xml:ns:yang:ietf-notification-capabilities
      Registrant Contact: The NETCONF WG of the IETF.
      XML: N/A, the requested URI is an XML namespace.

5.2.  The YANG Module Names Registry

   This document registers one YANG module in the YANG Module Names
   registry [RFC7950].  Following the format in [RFC7950], the the
   following registrations are requested:

  name:       ietf-notification-capabilities
  namespace:  urn:ietf:params:xml:ns:yang:ietf-notification-capabilities
  prefix:     inc
  reference:  RFC XXXX

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6.  References

6.1.  Normative References

   [I-D.ietf-netconf-rfc7895bis]
              Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
              and R. Wilton, "YANG Library", draft-ietf-netconf-
              rfc7895bis-04 (work in progress), January 2018.

   [I-D.ietf-netconf-yang-push]
              Clemm, A., Voit, E., Prieto, A., Tripathy, A., Nilsen-
              Nygaard, E., Bierman, A., and B. Lengyel, "YANG Datastore
              Subscription", draft-ietf-netconf-yang-push-14 (work in
              progress), February 2018.

   [I-D.lengyel-netmod-yang-instance-data]
              Lengyel, B. and B. Claise, "YANG Instance Data Files and
              their use for Documenting Server Capabilities", draft-
              lengyel-netmod-yang-instance-data-00 (work in progress),
              February 2018.

   [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>.

6.2.  Informative References

   [I-D.ietf-netmod-yang-tree-diagrams]
              Bjorklund, M. and L. Berger, "YANG Tree Diagrams", draft-
              ietf-netmod-yang-tree-diagrams-06 (work in progress),
              February 2018.

   [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>.

   [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>.

Authors' Addresses

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   Balazs Lengyel
   Ericsson
   Magyar Tudosok korutja 11
   1117 Budapest
   Hungary

   Email: balazs.lengyel@ericsson.com

   Alexander Clemm
   Huawei USA
   2330 Central Expressway
   Santa Clara, CA 95050
   USA

   Email: ludwig@clemm.org

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