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Versions: 00 01

NETCONF Working Group                                              Q. Wu
Internet-Draft                                                   W. Song
Intended status: Standards Track                                  Huawei
Expires: January 13, 2021                                        L. Geng
                                                                  P. Liu
                                                            China Mobile
                                                           July 12, 2020


               Adaptive Subscription to YANG Notification
              draft-wang-netconf-adaptive-subscription-01

Abstract

   This document defines a YANG data model and associated mechanism
   enabling subscriber's adaptive subscriptions to a publisher's event
   streams at various different period intervals with which to report
   updates.  Applying these elements allows both subscriber and
   publisher to automatically adjust the volume of telemetry traffic
   sent from publisher to the receivers.

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 January 13, 2021.

Copyright Notice

   Copyright (c) 2020 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, as they describe your rights and restrictions with respect



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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Model Overview  . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Subscription Configuration  . . . . . . . . . . . . . . .   5
     2.2.  YANG RPC  . . . . . . . . . . . . . . . . . . . . . . . .   6
       2.2.1.  "establish-subscription" RPC  . . . . . . . . . . . .   6
       2.2.2.  "modify-subscription" RPC . . . . . . . . . . . . . .   6
     2.3.  Notifications for Adaptive Subscribed Content . . . . . .   7
   3.  Adaptive Subscription YANG Module . . . . . . . . . . . . . .   7
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
     4.1.  Updates to the IETF XML Registry  . . . . . . . . . . . .  12
     4.2.  Updates to the YANG Module Names Registry . . . . . . . .  13
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  14
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  15
   Appendix A.  Example YANG Module  . . . . . . . . . . . . . . . .  15
     A.1.  "example-wifi-mac" YANG Module  . . . . . . . . . . . . .  16
   Appendix B.  Adaptive Subscription and Notification Example . . .  19
     B.1.  "edit-config" Example . . . . . . . . . . . . . . . . . .  19
     B.2.  Create Adaptive Subscription Example  . . . . . . . . . .  20
     B.3.  "adaptive-update" notification example  . . . . . . . . .  22
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  23

1.  Introduction

   YANG-Push subscriptions [RFC8641] allow client applications to
   subscribe to continuous datastore updates without needing to poll.
   It defines a mechanism (i.e.,update trigger) to determine when an
   update record needs to be generated.  Two type of subscriptions are
   introduced in [RFC8641], distinguished by how updates are triggered:
   periodic and on-change.

   o  Periodic subscription allows subscribed data to be streamed to the
      destination at a configured fixed periodic interval

   o  On-change subscription allows update to be triggered when whenever
      a change in the subscribed information is detected.  The periodic
      interval is set to zero value in the on-change subscription case.




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   However in some large scale deployments (e.g., wireless network
   performance monitoring) where an increased data collection rate is
   being used, it becomes more likely that a burst of streamed data may
   temporarily overwhelm a receiver and consume expensive network
   resource(e.g., air interface resource).  If the rate at which we can
   collect a stream of data is set too low, these telemetry data are not
   sufficient to detect and diagnose problems and verify correct network
   behavior.  There is a need for a service to configure both collectors
   and publishers with multiple period intervals, counter threshold and
   automatically switch to different period intervals according to
   resource usage, e.g., when the wireless signal strength falls below a
   configured low watermark, the subscribed data can be streamed at a
   higher rate while when the wireless signal strength crosses a
   configured high watermark, the subscribed data can be streamed at
   lower rate.

   This document defines a YANG data model and associated mechanism
   enabling subscriber's adaptive subscriptions to a publisher's event
   streams.  Applying these elements allows both subscriber and
   publisher to automatically adjust the volume of telemetry traffic
   sent from publisher to the receivers.

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.

   This document uses the following terms:

   Event:  An event is something that happens that may be of interest -
      a configuration change, a fault, a change in status, crossing a
      threshold, or an external input to the system, for example.
      Often, this results in an asynchronous message, sometimes referred
      to as a notification or event notification, being sent to
      interested parties to notify them that this event has occurred
      [RFC5277].

   Client:  Defined in [RFC8342].

   Configuration:   Defined in [RFC8342].

   Configured subscription:  Defined in [RFC8639]

   Configuration datastore:    Defined in [RFC8342].




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   Notification message:   Information intended for a receiver
      indicating that one or more events have occurred [RFC8639].

   Publisher:  An entity responsible for streaming notification messages
      per the terms of a subscription [RFC8639].

   Receiver:  A target to which a publisher pushes subscribed event
      records.  For dynamic subscriptions, the receiver and subscriber
      are the same entity [RFC8639].

   Subscriber:   A client able to request and negotiate a contract for
      the generation and push of event records from a publisher.  For
      dynamic subscriptions, the receiver and subscriber are the same
      entity [RFC8639].

   Subscription:  A contract with a publisher, stipulating the
      information that one or more receivers wish to have pushed from
      the publisher without the need for further solicitation [RFC8639].

   On-change subscription:  A datastore subscription with updates that
      are triggered when changes in subscribed datastore nodes are
      detected.

   Periodic subscription:  A datastore subscription with updates that
      are triggered periodically according to some time interval.

2.  Model Overview

   This document defines the YANG module "ietf-adaptive-subscription",
   which augments the "update-trigger" choice defined in the "ietf-yang-
   push" module [RFC8641] with subscription configuration parameters
   that are specific to adaptive subscription.

   In addition to Subscription state notifications defined in [RFC8639]
   and Notifications for Subscribed Content defined in [RFC8641], "ietf-
   adaptive-subscription" YANG module also defines "adaptive-update"
   notification.

   The following tree diagrams [RFC8340] provide an overview of the data
   model for "ietf-adaptive-subscription.yang" module.











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module: ietf-adaptive-subscription
  augment /sn:subscriptions/sn:subscription/yp:update-trigger:
    +--rw (adaptive-subscription)?
       +--:(adaptive-subscriptions)
          +--rw adaptive-subscriptions
             +--rw data-path?         yang:xpath1.0
             +--rw target?            <anydata>
             +--rw adaptive-period* [condition-expression]
                +--rw condition-expression    string
                +--rw watermark?              uint32
                +--rw period                  centiseconds
                +--rw count?                  uint16
                +--rw anchor-time?            yang:date-and-time
  augment /sn:establish-subscription/sn:input/yp:update-trigger:
    +-- (adaptive-subscription)?
       +--:(adaptive-subscriptions)
          +-- adaptive-subscriptions
             +-- data-path?         yang:xpath1.0
             +-- target?            <anydata>
             +-- adaptive-period* [condition-expression]
                +-- condition-expression    string
                +-- watermark?              uint32
                +-- period                  centiseconds
                +-- count?                  uint16
                +-- anchor-time?            yang:date-and-time

  notifications:
    +---n adaptive-period-update
       +--ro id?                                     sn:subscription-id
       +--ro period                                  centiseconds
       +--ro count?                                  uint16
       +--ro anchor-time?                            yang:date-and-time
       +--ro datastore                               identityref
       +--ro (selection-filter)?
          +--:(by-reference)
          |  +--ro selection-filter-ref              selection-filter-ref
          +--:(within-subscription)
             +--ro (filter-spec)?
                +--:(datastore-subtree-filter)
                |  +--ro datastore-subtree-filter?   <anydata> {sn:subtree}?
                +--:(datastore-xpath-filter)
                   +--ro datastore-xpath-filter?     yang:xpath1.0 {sn:xpath}?

2.1.  Subscription Configuration

   For adaptive subscriptions, triggered updates will occur at the
   boundaries of specified time intervals when a trigger condition is




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   satisfied.  These boundaries can be calculated from the adaptive
   periodic parameters:

   o  a "period" that defines the duration between push updates, the
      period can be changed based on trigger condition.

   o  a "count" that specifies the count number of interval that has to
      pass before successive adaptive periodic push update records for
      the same subscription are generated for a receiver.

   o  an "anchor-time"; update intervals fall on the points in time that
      are a multiple of a "period" from an "anchor-time".  If an
      "anchor-time" is not provided, then the "anchor-time" MUST be set
      with the creation time of the initial update record.

   o  a "high-watermark" that defines the upper boundary for the
      targeted data object.

   o  a "low-watermark" that defines the lower boundary for the targeted
      data object.

   o  a "data-path" identifies data path of the targeted data object.

   o  a "data" identifies the targeted data object that has been
      subscribed to.

   o  a "xpath-expression" represents a logical expression, which can
      contain comparisons of datastore values and logical operations in
      the XPath format.

2.2.  YANG RPC

2.2.1.  "establish-subscription" RPC

   The augmentation of YANG module ietf-yang-push made to RPCs specified
   in YANG module ietf-subscribed-notifications [RFC8639] is introduced.
   This augmentation concerns the "establish- subscription" RPC, which
   is augmented with parameters that are needed to specify adaptive
   subscriptions.  These parameters are same as one defined in
   Section 2.1.

2.2.2.  "modify-subscription" RPC

   The subscriber MAY invoke the "modify-subscription" RPC for a
   subscription it previously established.  The subscriber will include
   newly desired values in the "modify-subscription" RPC.  Parameters
   not included MUST remain unmodified.  Section 4.4.2 of [RFC8641]
   provides an example where a subscriber attempts to modify the period



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   and datastore XPath filter of a subscription using NETCONF.  The
   period can be the 'period' parameter defined by ietf-adaptive-
   subscription.

2.3.  Notifications for Adaptive Subscribed Content

   The adaptive update notification is similar to Subscription state
   change notifications defined in [RFC8639].  It is inserted into the
   sequence of notification messages sent to a particular receiver.  The
   adaptive update notification cannot be dropped or filtered out, it
   cannot be stored in replay buffers, and it is delivered only to
   impacted receivers of a subscription.  The identification of adaptive
   update notification is easy to separate from other notification
   messages through the use of the YANG extension "subscription-state-
   notif".  This extension tags a notification as a subscription state
   change notification.

   The objects in the 'adpative-update' notification include:

   o  a "period" that defines the duration between push updates, the
      period can be changed based on trigger condition.

   o  a "count" that specifies the count number of interval that has to
      pass before successive adaptive periodic push update records for
      the same subscription are generated for a receiver.

   o  an "anchor-time"; update intervals fall on the points in time that
      are a multiple of a "period" from an "anchor-time".  If an
      "anchor-time" is not provided, then the "anchor-time" MUST be set
      with the creation time of the initial update record.

   o  The targeted datastore from which the selection is being made.
      The potential datastores include those from [RFC8342].  A platform
      may also choose to support a custom datastore.

   o  A selection filter identifying YANG nodes of interest in a
      datastore.  Filter contents are specified via a reference to an
      existing filter or via an in-line definition for only that
      subscription.  Referenced filters allow an implementation to avoid
      evaluating filter acceptability during a dynamic subscription
      request.  The "case" statement differentiates the options.

3.  Adaptive Subscription YANG Module

<CODE BEGINS> file "ietf-adaptive-subscription@2020-02-14.yang"
module ietf-adaptive-subscription {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-adaptive-subscription";



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  prefix as;

  import ietf-subscribed-notifications {
    prefix sn;
  }
  import ietf-yang-push {
    prefix yp;
  }
  import ietf-yang-types {
    prefix yang;
  }

  organization
    "IETF NETCONF (Network Configuration) Working Group";
  contact
    "";
  description
    "NETCONF Protocol Data Types and Protocol Operations.
     Copyright (c) 2020 IETF Trust and the persons identified as
     the document authors.  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 Simplified BSD License
     set forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (http://trustee.ietf.org/license-info).

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

  revision 2019-12-15 {
    description
      "Initial revision";
    reference
      "RFCxxx Adaptive subscription to YANG notification.";
  }

  typedef centiseconds {
    type uint32;
    description
      "A period of time, measured in units of 0.01 seconds.";
  }

  typedef seconds {
    type uint32;
    description
      "A period of time, measured in units of 1 seconds.";



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  }

  typedef operator {
    type enumeration {
      enum unequal {
        description
          "Indicates that the comparision type is unequal to.";
      }
      enum equal {
        description
          "Indicates that the comparision type is equal to.";
      }
      enum less {
        description
          "Indicates that the comparision type is less than.";
      }
      enum less-or-equal {
        description
          "Indicates that the comparision type is less than
           or equal to.";
      }
      enum greater {
        description
          "Indicates that the comparision type is greater than.";
      }
      enum greater-or-equal {
        description
          "Indicates that the comparision type is greater than
           or equal to.";
      }
    }
    description
      "definition of the operator";
  }

  grouping adaptive-subscription-modifiable {
    description
      "This grouping describes the datastore-specific adaptive subscription
       conditions that can be changed during the lifetime of the
       subscription.";
    choice adaptive-subscription {
      description
        "Defines necessary conditions for sending an event record to
               the subscriber.";
      container adaptive-subscriptions {
        leaf data-path {
          type yang:xpath1.0;
          description



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            "The data path of targeted object";
        }
        anydata target {
          description
            " The targeted data object that has been subscribed to.";
        }
        list adaptive-period {
          key "condition-expression";
          description
            "Defines necessary conditions for sending an event record to
                   the subscriber.";
          leaf condition-expression {
            type string;
            description
              "A XPath string, representing a logical expression,
                       which can contain comparisons of datastore values
                       and logical operations in the XPath format.";
          }
          leaf watermark {
            type uint32;
            description
              "The watermark for targeted data object. The high
               watermark, lowe watermark can be specified for the
               targeted data object.";
          }
          leaf period {
            type centiseconds;
            mandatory true;
            description
              "Duration of time that should occur between periodic
               push updates, in units of 0.01 seconds.";
          }
          leaf count {
            type uint16;
            description
              "specify the count number of interval that has to pass before
               successive adaptive periodic push update records for the same
               subscription are generated for a receiver.";
          }
          leaf anchor-time {
            type yang:date-and-time;
            description
              "Designates a timestamp before or after which a series
               of periodic push updates are determined.  The next
               update will take place at a point in time that is a
               multiple of a period from the 'anchor-time'.
               For example, for an 'anchor-time' that is set for the
               top of a particular minute and a period interval of a



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               minute, updates will be sent at the top of every
               minute that this subscription is active.";
          }
        }
        description
          "Container for adaptive subscription.";
      }
    }
  }

  augment "/sn:subscriptions/sn:subscription/yp:update-trigger" {
    description
      "This augmentation adds additional subscription parameters
       that apply specifically to adaptive subscription.";
    uses adaptive-subscription-modifiable;
  }
  augment "/sn:establish-subscription/sn:input/yp:update-trigger" {
    description
      "This augmentation adds additional subscription parameters
         that apply specifically to datastore updates to RPC input.";
    uses adaptive-subscription-modifiable;
  }

  notification adaptive-period-update {
    sn:subscription-state-notification;
    description
      "This notification contains a push update that in turn contains
       data subscribed to via a subscription.  In the case of a
       periodic subscription, this notification is sent for periodic
       updates.  It can also be used for synchronization updates of
       an on-change subscription.  This notification shall only be
       sent to receivers of a subscription.  It does not constitute
       a general-purpose notification that would be subscribable as
       part of the NETCONF event stream by any receiver.";
    leaf id {
      type sn:subscription-id;
      description
        "This references the subscription that drove the
         notification to be sent.";
    }
    leaf period {
      type centiseconds;
      mandatory true;
      description
        "Duration of time that should occur between periodic
         push updates, in units of 0.01 seconds.";
    }
    leaf count {



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      type uint16;
      description
        "specify the count number of interval that has to pass before
         successive adaptive periodic push update records for the same
         subscription are generated for a receiver.";
    }
    leaf anchor-time {
      type yang:date-and-time;
      description
        "Designates a timestamp before or after which a series
         of periodic push updates are determined.  The next
         update will take place at a point in time that is a
         multiple of a period from the 'anchor-time'.
         For example, for an 'anchor-time' that is set for the
         top of a particular minute and a period interval of a
         minute, updates will be sent at the top of every
         minute that this subscription is active.";
    }
    uses yp:datastore-criteria {
      refine "selection-filter/within-subscription" {
        description
          "Specifies the selection filter and where it originated
           from.  If the 'selection-filter-ref' is populated, the
           filter in the subscription came from the 'filters'
           container.  Otherwise, it is populated in-line as part
           of the subscription itself.";
      }
    }
  }
}
<CODE ENDS>

4.  IANA Considerations

4.1.  Updates to the IETF XML Registry

   This document registers two URIs in the IETF XML registry [RFC3688].
   Following the format in [RFC3688], the following registrations are
   requested to be made:

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






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4.2.  Updates to the YANG Module Names Registry

   This document registers two YANG modules in the YANG Module Names
   registry [RFC7950]. . Following the format in [RFC6020], the
   following registration has been made:

   ---------------------------------------------------------------------
      Name:         ietf-adaptive-subscription
      Namespace:    urn:ietf:params:xml:ns:yang:ietf-adaptive-subscription
      Prefix:       as
      Reference:    RFC xxxx
   ---------------------------------------------------------------------

5.  Security Considerations

   The YANG module 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 NETCONF 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.

   There are a number of data nodes defined in this YANG module that are
   writable/creatable/deletable (i.e., config true, which is the
   default).  These data nodes may be considered sensitive in some
   network environments.  Write operations (e.g., edit-config) to these
   data nodes without proper protection can have a negative effect on
   network operations.  These are the subtrees and data nodes and their
   sensitivity/vulnerability:

   o  /sn:subscriptions/sn:subscription/yp:update-trigger/as:adaptive-
      subscriptions/as:adaptive-period/as:high-watermark

   o  /sn:subscriptions/sn:subscription/yp:update-trigger/as:adaptive-
      subscriptions/as:adaptive-period/as:low-watermark

   o  /sn:subscriptions/sn:subscription/yp:update-trigger/as:adaptive-
      subscriptions/as:adaptive-period/as:period

   o  /sn:subscriptions/sn:subscription/yp:update-trigger/as:adaptive-
      subscriptions/as:adaptive-period/as:period2




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   o  /sn:subscriptions/sn:subscription/yp:update-trigger/as:adaptive-
      subscriptions/as:adaptive-period/as:anchor-time

   o  /sn:subscriptions/sn:subscription/yp:update-trigger/as:adaptive-
      subscriptions/as:adaptive-period/as:anchor-time2

6.  Contributors

   The authors would like to thank Michale Wang for his major
   contributions to the initial modeling and use cases.

7.  References

7.1.  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>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [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>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [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>.






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   [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>.

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

   [RFC8407]  Bierman, A., "Guidelines for Authors and Reviewers of
              Documents Containing YANG Data Models", BCP 216, RFC 8407,
              DOI 10.17487/RFC8407, October 2018,
              <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, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC8641]  Clemm, A. and E. Voit, "Subscription to YANG Notifications
              for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641,
              September 2019, <https://www.rfc-editor.org/info/rfc8641>.

7.2.  Informative References

   [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>.

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

Appendix A.  Example YANG Module

   The example YANG module used in this document represents a simple
   wifi mac interface.

   YANG tree diagram for the "example-wifi-mac" module:







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   module: example-wifi-mac
     +--rw clients
        +--ro client* [mac]
           +--ro mac                yang:mac-address
           +--ro rssi?              int8
           +--ro snr?               uint8
           +--ro ss?                uint8
           +--ro phy-rate?          uint16
           +--ro channel-support*   uint8
           +--ro neighbors
           |  +--ro neighbor-bssid?          yang:mac-address
           |  +--ro neighbor-channel?        uint8
           |  +--ro neighbor-rssi?           int8
           |  +--ro neighbor-antenna?        uint8
           |  +--ro channel-load-report?     uint8
           +--ro ssid
              +--ro name?                    string
              +--ro enabled?                 boolean
              +--ro broadcast-filter?        boolean
              +--ro multicast-filter?        boolean
              +--ro ipv6-ndp-filter?         boolean
              +--ro ipv6-ndp-filter-timer?   uint16
              +--ro station-isolation?       boolean

A.1.  "example-wifi-mac" YANG Module

module example-wifi-mac {
  yang-version 1;
  namespace "http://example.com/yang/wifi-mac";
  prefix wifi;

  import ietf-yang-types {
    prefix yang;
  }

  container clients {
    description
      "Top-level container for clients operational state data.";
    list client {
      key "mac";
      config false;
      description
        "List of clients per BSS.";
      leaf mac {
        type yang:mac-address;
        description
          "MAC address of the client.";
      }



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      leaf rssi {
        type int8;
        description
          "The RSSI of this client in dBm. Expressed as negative
           number";
      }
      leaf snr {
        type uint8;
        description
          "The SNR of AP to Client, in dB.";
      }
      leaf ss {
        type uint8;
        description
          "Number of Spatial Streams supported by the client.";
      }
      leaf phy-rate {
        type uint16;
        description
          "Last used PHY rate of connected client.";
      }
      leaf-list channel-support {
        type uint8;
        description
          "List of supported channels.";
      }
      container neighbors {
        description
          "Container for Client beacon reports. Requires 802.11k
           enabled. See Sec. 5.2.7.1 of 802.11k-2008 Standard.";
        leaf neighbor-bssid {
          type yang:mac-address;
          description
            "The BSSID of this neighbor.";
        }
        leaf neighbor-channel {
          type uint8;
          description
            "The channel of this neighbor.";
        }
        leaf neighbor-rssi {
          type int8;
          description
            "The RSSI of this neighbor in dBm, expressed as a negative
             number.";
        }
        leaf neighbor-antenna {
          type uint8;



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          description
            "Antenna details for this neighbor.";
        }
        leaf channel-load-report {
          type uint8;
          description
            "Channel load, as reported by Client to AP
             normalized to 255. See Sec. 10.11.9.3 of 802.11ac-2013
             Spec.";
        }
      }
      container ssid {
        description
          "Top level container for ssids, including configuration
           and state data.";
        leaf name {
          type string;
          description
            "The name of the SSID.";
        }
        leaf enabled {
          type boolean;
          default "true";
          description
            "The desired operational state (up/down) of this SSID.";
        }
        leaf broadcast-filter {
          type boolean;
          description
            "Convert all downstream broadcast ARP to unicast
             only if Station is associated to the AP. Drop packet
             if Station is not associated to the AP. All other
             broadcast, except DHCP, is dropped by the AP.

             DHCP Offers/ACKs are converted to Unicast, over-the-air.";
        }
        leaf multicast-filter {
          type boolean;
          description
            "Drop all downstream Multicast packets.";
        }
        leaf ipv6-ndp-filter {
          type boolean;
          description
            "Neighbor Advertisements will be cached at the AP (or WLC)
             and unicast in response to Neighbor Solicitations.

             Router Advertisements, in response to a Router Solicitation



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             are converted to Unicast for over-the-air transmission.";
        }
        leaf ipv6-ndp-filter-timer {
          type uint16;
          units "seconds";
          description
            "Time, in seconds, the ndp-filter will cache
             Neighbor Advertisements (NA).";
        }
        leaf station-isolation {
          type boolean;
          description
            "Block Station peer to peer communication.";
        }
      }
    }
  }
}

Appendix B.  Adaptive Subscription and Notification Example

   The examples within this document use the normative YANG module
   "ietf-adaptive-subscription" as defined in Section 3 and the non-
   normative example YANG module "example-wifi-mac" as defined in
   Appendix A.1.

   This section shows some typical adaptive subscription and
   notification message exchanges.

B.1.  "edit-config" Example

   The client configure adaptive subscription parameters on the server.
   The adaptive subscription configuration parameters require the server
   to scan all clients every 5 seconds up to 30 seconds if the ssid
   value of client is greater than -65dB; If the ssid value of client is
   less than -65dB, switch to 60 seconds period value, and then scan all
   client every 60 seconds up to 360 seconds. 30 seconds and 360 seconds
   can be seen as time window.  The time window lenght is 6 period
   values.  Irrespective of period value set for adaptive subscription,
   6 event records during the time window should be generated for the
   same subscription and send to the receivers.










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     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <edit-config>
         <target>
           <running/>
         </target>
         <config xmlns:xc="urn:ietf:params:xml:ns:netconf:base:1.0">
           <top xmlns="http://example.com/schema/1.2/config">
           <yp:datastore
             xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
             ds:running
           </yp:datastore>
          <yp:datastore-xpath-filter
            xmlns:ex="https://example.com/sample-data/1.0">
            /ex:example-wifi-mac
         </yp:datastore-xpath-filter>
       <as:adaptive-subscriptions
      xmlns:as="urn:ietf:params:xml:ns:yang:ietf-adaptive-subscription">
        <as:data-path>as:clients/as:client</as:data-path>
        <as:target>ssid</as:target>
       <as:adaptive-period>
        <as:condition-expression>ssid > -65</as:condition-expressioni>
        <as:watermark>-65</as:watermark>
        <as:period>5</as:period>
         <as:count>12</as:count>
       </as:adaptive-period>
       <as:adaptive-period>
        <as:condition-expression>ssid < -65</as:condition-expressioni>
        <as:watermark>-65</as:watermark>
        <as:period>60</as:period>
         <as:count>12</as:count>
       </as:adaptive-period>
      </as:adaptive-subscriptions>
           </top>
         </config>
       </edit-config>
     </rpc>

B.2.  Create Adaptive Subscription Example

   The subscriber sends an "establish-subscription" RPC with the
   parameters listed in to request the creation of a adaptive
   subscription.  The adaptive subscription configuration parameters
   require the server to scan all clients every 5 seconds up to 60
   seconds if the ssid value of client is greater than -65dB; If the
   ssid value of client is less than -65dB, switch to 60 seconds period
   value, and then scan all client every 60 seconds up to 720 seconds.
   (Section 2)



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<netconf:rpc message-id="101"
     xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
   <establish-subscription
       xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
       xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
     <yp:datastore
          xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
       ds:running
     </yp:datastore>
     <yp:datastore-xpath-filter
         xmlns:ex="https://example.com/sample-data/1.0">
       /ex:example-wifi-mac
     </yp:datastore-xpath-filter>
     <as:adaptive-subscriptions
    xmlns="urn:ietf:params:xml:ns:yang:ietf-adaptive-subscription">
        <as:data-path>as:clients/as:client</as:data-path>
        <as:target>ssid</as:target>
       <as:adaptive-period>
        <as:condition-expression>ssid > -65</as:condition-expressioni>
        <as:watermark>-65</as:watermark>
        <as:period>5</as:period>
         <as:count>12</as:count>
       </as:adaptive-period>
       <as:adaptive-period>
        <as:condition-expression>ssid < -65</as:condition-expressioni>
        <as:watermark>-65</as:watermark>
        <as:period>60</as:period>
         <as:count>12</as:count>
       </as:adaptive-period>
     </as:adaptive-subscriptions>
   </establish-subscription>
 </netconf:rpc>

   In another example, the adaptive subscription configuration
   parameters could also require the server to scan all clients every 5
   seconds up to 60 seconds if the difference between maximum value of
   client ssid and minimum value of client ssid is greater than 0.20dB;
   If the difference between maximum value of client ssid and minimum
   value of client ssid is less than 20dB, switch to 60 seconds period
   value and then scan all client every 60 seconds up to 720 seconds.











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<netconf:rpc message-id="101"
     xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
   <establish-subscription
       xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
       xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
     <yp:datastore
          xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
       ds:running
     </yp:datastore>
     <yp:datastore-xpath-filter
         xmlns:ex="https://example.com/sample-data/1.0">
       /ex:example-wifi-mac
     </yp:datastore-xpath-filter>
     <as:adaptive-subscriptions>
        <as:data-path>as:clients/as:client</as:data-path>
        <as:target>ssid</as:target>
       <as:adaptive-period>
        <as:condition-expression>max(ssid)-min(ssid) >20</as:condition-expressioni>
        <as:watermark>20</as:watermark>
        <as:period>5</as:period>
         <as:count>12</as:count>
       </as:adaptive-period>
       <as:adaptive-period>
        <as:condition-expression>max(ssid)-min(ssid) < 20</as:condition-expressioni>
        <as:watermark>20</as:watermark>
        <as:period>60</as:period>
         <as:count>12</as:count>
       </as:adaptive-period>
     </as:adaptive-subscriptions>
   </establish-subscription>
 </netconf:rpc>

B.3.  "adaptive-update" notification example

   Upon the server switches to from the update interval 5 seconds to the
   new update interval 60 seconds, in addition to sending event records
   to receivers, the "adaptive-update" notification should be generated
   and sent to the receivers to inform the receivers that the update
   interval value is switched to the new value.












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<notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
  <eventTime>2016-11-21T13:51:00Z</eventTime>
  <adaptive-update xmlns="http://example.com/ietf-adaptive-subscription">
    <id>0</id>
    <period>60</period>
     <yp:datastore
          xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
       ds:running
     </yp:datastore>
     <yp:datastore-xpath-filter
         xmlns:ex="https://example.com/sample-data/1.0">
       /ex:example-wifi-mac
     </yp:datastore-xpath-filter>
  </adaptive-update>
</notification>

Authors' Addresses

   Qin Wu
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: bill.wu@huawei.com


   Wei Song
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: songwei80@huawei.com


   Liang Geng
   China Mobile
   32 Xuanwumen West St, Xicheng District
   Beijing  10053

   Email: gengliang@chinamobile.com









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   Peng Liu
   China Mobile
   32 Xuanwumen West St, Xicheng District
   Beijing  10053

   Email: liupengyjy@chinamobile.com













































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