NETCONF Working Group Z. Wang
Internet-Draft Q. Wu
Intended status: Standards Track W. Song
Expires: September 4, 2020 Huawei
L. Geng
P. Liu
China Mobile
March 3, 2020

Adaptive Subscription to YANG Notification
draft-wang-netconf-adaptive-subscription-00

Abstract

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 a subscriber 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 September 4, 2020.

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 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

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.

However in some cases (e.g., wireless channel contention and interference causes the WLAN throughput and per-packet delays to vary over time), both collectors and publishers are configured with multiple periodic intervals and the subscribed data set can be streamed out to the destination at adaptive sampling or export rate, e.g., when wireless signal strength drops below a certain threshold, more data should be collected at high frequency.

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 a subscriber 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:
Something that happens which may be of interest or trigger the invocation of the rule. A fault, an alarm, a change in network state, network security threat, hardware malfunction, buffer untilization crossing a threshold, network connection setup, an external input to the system, for example [RFC3877].
Client:
Defined in [RFC8342].
Configuration:
Defined in [RFC8342].
Configured subscription:
Defined in [RFC8639]
Configuration datastore:
Defined in [RFC8342].
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

The YANG data model for the "Adaptive Subscription to YANG Notification" augments the "update-trigger" in the YANG Push model to add a "adaptive-period" case. Under the "adaptive-period" case, a "adaptive-period" list is defined. The "adaptive-period" list uses the key "id" for indexing. Within the "adaptive-period" list, an "interval" leaf and the corresponding trigger conditions are defined. When the trigger condition is satisfied, e.g., "op-field" exceeds the "op-value" and the change of "op-field" is monotonically increasing, the update interval will be changed into the value of "interval" leaf and the objects being filtered will be exported every interval specified by the value of "interval" leaf. The "anchor-time" is used to indciate at which points in time periodic updates need to be assembled and sent.

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

module: ietf-adaptive-subscription
  augment /sn:subscriptions/sn:subscription/yp:update-trigger:
    +--:(adaptive-subscription)
       +--rw adaptive-subsciptions
          +--rw adaptive-period* [id]
          |   +--rw id              string
          |   +--rw op-field?       yang:xpath1.0
          |   +--rw op-value?       string
          |   +--rw operator?       operator
          |   +--rw interval          centiseconds
          |   +--rw anchor-time       yang:date-time

3. Bulk 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";
  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 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";
  }  
  augment "/sn:subscriptions/sn:subscription/yp:update-trigger" {
         description
         "This augmentation adds additional subscription parameters
          that apply specifically to adaptive subscription.";
    case adaptive-period {
      container adaptive-periods {
        list adaptive-period {
          key "id";
          leaf id {
            type string;
            description
              "identifier";
          }
          leaf op-field {
            type yang:xpath1.0;
            description
              "targeted objects";
          }
          leaf op-value {
            type string;
            description
              "Compartion value which is static threshold value.";
          }
          leaf operator {
            type operator;
            description
              "Comparison type."; 
          }
         leaf interval {
            type centiseconds;
            mandatory true;
            description
              "Duration of time that should occur between periodic
               push updates, in units of 0.01 seconds.";
        }
        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'.
               If an anchor-time is not provided, then the anchor-time 
               MUST be set with the creation time of the initial 
               update record. ";
             }
        description
          "List for adaptive periods";
      }
	  description
	     "Container for adaptive periods.";
    }
  }
 }
}
<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.
   ---------------------------------------------------------------------

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:

6. 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.
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J. and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011.
[RFC7950] Bjorklund, M., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016.
[RFC8040] Bierman, A., Bjorklund, M. and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017.
[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.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018.
[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.
[RFC8407] Bierman, A., "Guidelines for Authors and Reviewers of Documents Containing YANG Data Models", BCP 216, RFC 8407, DOI 10.17487/RFC8407, October 2018.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018.
[RFC8641] Clemm, A. and E. Voit, "Subscription to YANG Notifications for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641, September 2019.

6.2. Informative References

[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010.
[RFC8340] Bjorklund, M. and L. Berger, "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018.

Appendix A. Adaptive Subscription Example

The example YANG module used in this document represents performance data telemetry on a simple optical device. The collector can control the rate of telemtry data to be streamed to the destination by switching to different time interval for the update to be sent.

       module example-opticalbox-telemetry {
           namespace "tag:ietf:example:opticalbox";
           prefix "optibox";
           container opticalstat {
               leaf transmit-power {
                   description "Transmit optical power reading";
                   type int;
                   config false;
               }
               leaf receiving-power {
                   description " Receiving optical power reading";
                   type int;
                   config false;
               }
               leaf power-threhold {
                   description "Optical Power Threshold";
                   type int;
               }
               leaf high-voltage {
                   description "High voltage threshold";
                   type int;
               }
               leaf low-voltage {
                   description "Low voltage threshold";
                   type int;
               }
               leaf voltage {
                   description "current voltage reading";
                   type int;
                 config false;
               }
               leaf current-temperature {
                   description "Current temperature reading";
                   type int;
                   config false;
               }
               leaf cup-usage {
                 type uint32;
                 config false;
            }
           }
       }

YANG tree diagram for the "example-opticalbox-telemetry" module:

The adaptive subscription model can be used to keep track of performance data change such as temperature, voltage, power,cup usage. In addition, it can adjust update period based on performance data change, e.g., when the current receiving power is higher than the pre-configured threshold, the notification for the optical performance data from publisher can be sent at a low frequency. When the current receiving power is lower than the pre-configured threshold, the notification for the optical performance data can be sent at a high frequency.

<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:operational
     </yp:datastore>
     <yp:datastore-xpath-filter
         xmlns:ex="https://example.com/sample-data/1.0">
       /ex:foo
     </yp:datastore-xpath-filter>
     <as:adaptive-periods>
       <as:adaptive-period>
        <as:id>01</as:id>
        <as:op-field>/opticalstat/current-voltage</as:op-field>
        <as:op-value>60</as:op-value>
        <as:operator>greater</as:operator>
        <as:period>500</as:period>
       </as:adaptive-period>
       <as:adaptive-period>
        <as:id>02</as:id>
        <as:op-field>/opticalstat/current-voltage</as:op-field>
        <as:op-value>60</as:op-value>
        <as:operator>less-or-equal</as:operator>
        <as:period>100</as:period>
       </as:adaptive-period>
     </yp:adaptive-periods>
   </establish-subscription>
 </netconf:rpc>

In another example, when the time interval for update to be sent is set to 5 seconds and specific performance data,e.g., 5 receiving power values (0.48dB、0.57dB、0.61dB、0.69dB、0.70dB) can be sampled per second and collected during this time interval changes. When power changes exceed the preconfigured threhold (e.g.,0.20dB), all these 5 receiving power values falling within detection time window or update time interval should be published to the destinations for data analysis.

Authors' Addresses

Michael Wang Huawei 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China EMail: wangzitao@huawei.com
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
Peng Liu China Mobile 32 Xuanwumen West St, Xicheng District Beijing, 10053 EMail: liupengyjy@chinamobile.com