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NETCONF                                                          T. Zhou
Internet-Draft                                                  G. Zheng
Intended status: Standards Track                                  Huawei
Expires: May 7, 2020                                             E. Voit
                                                           Cisco Systems
                                                                A. Clemm
                                                               Futurewai
                                                        November 4, 2019


              Subscription to Multiple Stream Originators
             draft-zhou-netconf-multi-stream-originators-10

Abstract

   This document describes the distributed data export mechanism that
   allows multiple data streams to be managed by using a single
   subscription.  Specifically, device can decide to decompse one
   subscription into multiple subscriptions to the line-cards.  So that
   each line-card can directly push data to the collector without
   passing through a broker for internal consolidation.  And the device
   can indicate the subscription decomposition result to the receiver to
   check the data integrity.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

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 May 7, 2020.





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Copyright Notice

   Copyright (c) 2019 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Data Collection from Devices with Main-board and Line-cards .   3
   3.  Terminologies . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Solution Overview . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Subscription Decomposition  . . . . . . . . . . . . . . . . .   7
   6.  Publication Composition . . . . . . . . . . . . . . . . . . .   8
   7.  Subscription State Change Notifications . . . . . . . . . . .   9
   8.  Publisher Configurations  . . . . . . . . . . . . . . . . . .   9
   9.  YANG Tree . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   10. YANG Module . . . . . . . . . . . . . . . . . . . . . . . . .  10
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   12. Transport Considerations  . . . . . . . . . . . . . . . . . .  12
   13. Security Considerations . . . . . . . . . . . . . . . . . . .  12
   14. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   15. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     15.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     15.2.  Informative References . . . . . . . . . . . . . . . . .  14
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  15
     A.1.  Dynamic Subscription  . . . . . . . . . . . . . . . . . .  15
     A.2.  Configured Subscription . . . . . . . . . . . . . . . . .  18
   Appendix B.  Change Log . . . . . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  22

1.  Introduction

   Streaming telemetry refers to sending a continuous stream of
   operational data from a device to a remote receiver.  This provides
   an ability to monitor a network from remote and to provide network
   analytics.  Devices generate telemetry data and push that data to a
   collector for further analysis.  By streaming the data, much better
   performance, finer-grained sampling, monitoring accuracy, and



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   bandwidth utilization can be achieved than with polling-based
   alternatives.

   Mechanisms to support subscription to event notifications have been
   defined in[RFC8639] and [RFC8641].  The current design involves
   subscription to a single push server.  This conceptually centralized
   model encounters efficiency limitations in cases where the data
   sources are themselves distributed, such as line cards in a piece of
   network equipment.  In such cases, it will be a lot more efficient to
   have each data source (e.g., each line card) originate its own stream
   of updates, rather than requiring updates to be tunneled through a
   central server where they are combined.  What is needed is a
   distributed mechanism that allows to directly push multiple
   individual data substreams, without needing to first pass them
   through an additional processing stage for internal consolidation,
   but still allowing those substreams to be managed and controlled via
   a single subscription.

   This document will describe such distributed data export mechanism
   and how it can work by extending existing push mechanism.
   Specifically, device can decide to decompse one subscription into
   multiple subscriptions to the line-cards.  So that each line-card can
   directly push data to the collector without passing through a broker
   for internal consolidation.  And the device can indicate the
   subscription decomposition result to the receiver to check the data
   integrity.  The proposal will focus on the scenario when data
   collection from devices with main-board and line-cards.  It could be
   generalized to other distributed data export scenarios.

2.  Data Collection from Devices with Main-board and Line-cards

   For data collection from devices with main-board and line-cards,
   existing push solutions consider only one push server typically
   reside in the main board.  As shown in the following figure, data are
   collected from line cards and aggregate to the main board as one
   consolidated stream.  So the main board can easily become the
   performance bottle-neck.  The optimization is to apply the
   distributed data export mechanism which can directly push data from
   line cards to a collector.  On one hand, this will reduce the cost of
   scarce compute and memory resources on the main board for data
   processing and assembling.  On the other hand, distributed data push
   can off-load the streaming traffic to multiple interfaces.









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                  +-------------------------------------+
                  |              collector              |
                  +------^-----------^-----------^------+
                         |           |           |
                         |           |           |
                  +-------------------------------------+
                  |      |           |           |      |
                  |      |     +-----+------+    |      |
                  |      |     | main board |    |      |
                  |      |     +--^-----^---+    |      |
                  |      |        |     |        |      |
                  |      |    +---+     +---+    |      |
                  |      |    |             |    |      |
                  | +----+----+---+     +---+----+----+ |
                  | | line card 1 |     | line card 2 | |
                  | +-------------+     +-------------+ |
                  |               device                |
                  +-------------------------------------+

    Fig. 1 Data Collection from Devices with Main-board and Line-cards

3.  Terminologies

   The following terms are defined in [RFC8639] and are not redefined
   here:

   Subscriber

   Publisher

   Receiver

   Subscription

   In addition, this document defines the following terms:

   Global Subscription: the Subscription requested by the subscriber.
   It may be decomposed into multiple Component Subscriptions.

   Component Subscription: is the Subscription that defines the data
   from each individual telemetry source which is managed and controlled
   by a single Publisher.

   Global Capability: is the overall subscription capability that the
   group of Publishers can expose to the Subscriber.

   Component Capability: is the subscription capability that each
   Publisher can expose to the Subscriber.



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   Master: is the Publisher that interacts with the Subscriber to deal
   with the Global Subscription.  It decomposes the Global Subscription
   to multiple Component Subscriptions and interacts with the Agents.

   Agent: is the Publisher that interacts with the Master to deal with
   the Component Subscription.

4.  Solution Overview

   Figure 2 below shows the distributed data export framework.

   A collector usually includes two components,

   o  the Subscriber generates the subscription instructions to express
      what and how the collector want to receive the data;

   o  the Receiver is the target for the data publication.

   For one subscription, there may be one to many Receivers.  And the
   Subscriber does not necessarily share the same address with the
   Receivers.

   In this framework, the Publisher pushes data to the Receiver
   according to the subscription information.  The Publisher has the
   Master role and the Agent role.  The Master knows all the
   capabilities that the attached Agents and itself can provide, and
   exposes the Global Capability to the collector.  The collector cannot
   see the Agents directly, so it will only send the Global Subscription
   information to the Master.  The Master disassembles the Global
   Subscription to multiple Component Subscriptions, each involving data
   from a separate telemetry source.  The Component Subscriptions are
   then distributed to the corresponding Agents.

   When data streaming, the Publisher collects and encapsulates the
   packets per the Component Subscription, and pushes the piece of data
   which can serve directly to the designated data collector.  The
   collector is able to assemble many pieces of data associated with one
   Global Subscription, and can also deduce the missing pieces of data.













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                +-----------------------------------------+
                |        Collector        |-------------+ |
                |                        +------------+ | |
                |      +------------+    || Receiver  | | |
                |      | Subscriber |    |--------------+ |
                |      +-----^-+----+    +-----^------^   |
                |            | |               |      |   |
                +-----------------------------------------+
                   Global    | | Global        |      |
                   Capability| | Subscription  |      |
                +-----------------------------------------+
                |            | |          Push |      |   |
                |   +--------+-v---------------+---+  |   |
                |   |       Publisher(Master)      |  |   |
                |   +--------^-+-------------------+  |   |
                |            | |                      |   |
                |            | |                      |   |
                |  Component | | Component       Push |   |
                |  Capability| | Subscription         |   |
                |   +--------+-v-------------------+  |   |
                |   |       Publisher(Agent)       +--+   |
                |   +------------------------------+      |
                |                                         |
                |                Device                   |
                +-----------------------------------------+


               Fig. 2 The Distributed Data Export Framework

   Master and Agents may interact with each other in several ways:

   o  Agents need to have a registration or announcement handshake with
      the Master, so the Master is aware of them and of life-cycle
      events (such as Agent appearing and disappearing).

   o  Contracts are needed between the Master and each Agent on the
      Component Capability, and the format for streaming data structure.

   o  The Master relays the component subscriptions to the Agents.

   o  The Agents indicate status of Component Subscriptions to the
      Master.  The status of the overall subscription is maintained by
      the Master.  The Master is also responsible for notifying the
      subscriber in case of any problems of Component Subscriptions.

   Any technical mechanisms or protocols used for the coordination of
   operational information between Master and Agent is out-of-scope of




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   this document.  We will need to instrument the results of this
   coordination on the Master.

5.  Subscription Decomposition

   The Collector can only subscribe to the Master.  This requires the
   Master to:

   1.  expose the Global Capability that can be served by multiple
       Publishers;

   2.  disassemble the Global Subscription to multiple Component
       Subscriptions, and distribute them to the corresponding telemetry
       sources;

   3.  notify on changes when portions of a subscription moving between
       different Agents over time.

   The Master can keep track of the mapping between the resource and the
   corresponding location of the Publisher which commits to serve the
   data.  If a Publisher does not have external connectivity or
   permission to export, the master MUST NOT decompose a component
   subscription to that Publisher.  In some implementations, the Global
   Subscription can be disassembled into multiple Component
   Subscriptions according to the Resource-Location Table, and the
   corresponding location can be associated.  The decision whether to
   decompose a Global Subscription into multiple Component Subscriptions
   rests with the Resource-Location Table.  A Master can decide to not
   decompose a Global Subscription at all and push a single stream to
   the receiver, because the location information indicates the Global
   Subscription can be served locally by the Master.  Similarly, it can
   decide to entirely decompose a Global Subscription into multiple
   Component Subscriptions that each push their own streams, but not
   from the Master.  It can also decide to decompose the Global
   Subscription into several Component Subscriptions and retain some
   aspects of the Global Subscription itself, also pushing its own
   stream.

   Component Subscriptions belonging to the same Global Subscription
   MUST NOT overlap.  The combination of all Component Subscriptions
   MUST cover the same range of nodes as the Global Subscription.  Also,
   the same subscription settings apply to each Component Subscription,
   i.e., the same receivers, the same time periods, the same encodings
   are applied to each Component Subscription per the settings of the
   Global Subscription.

   Each Component Subscription in effect constitutes a full-fledged
   subscription, with the following constraints:



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   o  Component subscriptions are system-controlled, i.e. managed by the
      Master, not by the subscriber.

   o  Component subscription settings such as time periods, dampening
      periods, encodings, receivers adopt the settings of their Global
      Subscription.

   o  The life-cycle of the Component Subscription is tied to the life-
      cycle of the Global Subscription.  Specifically, terminating/
      removing the Global Subscription results in termination/removal of
      Component Subscriptions.

   o  The Component Subscriptions share the same Subscription ID as the
      Global Subscription.

6.  Publication Composition

   The Publisher collects data and encapsulates the packets per the
   Component Subscription.  There are several potential encodings,
   including XML, JSON, CBOR and GPB.  The format and structure of the
   data records are defined by the YANG schema, so that the composition
   at the Receiver can benefit from the structured and hierarchical data
   instance.

   The Receiver is able to assemble many pieces of data associated with
   one subscription, and can also deduce the missing pieces of data.
   The Receiver recognizes data records associated with one subscription
   according the Subscription ID [RFC8639].  Data records generated per
   one subscription are assigned with the same Subscription ID.

   For the periodic updates, records are produced periodically from each
   Publisher.  The message arrival time varies because of the
   distributed nature of the publication.  The Receiver assembles data
   generated at the same time period based on the recording time
   consisted in each data record.  In this case, time synchronization is
   required for all the Publishers.

   Message Generator ID [I-D.ietf-netconf-notification-messages] is the
   identifier for the process which created the notification message.
   It's contained in every notification messages, and allows
   disambiguation of different line cards sending the messages.  This
   document, in addition, requires the device to notify collector the
   set of Message Generator IDs standing for the Publishers serving for
   one Global Subscription.  So that the collector can easily check the
   integrity of the data collected from different Publishers at the same
   time period.  And the collector can deduce the Publishers which are
   responsible for the missing pieces of data.




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   For the dynamic subscription, the output of the "establish-
   subscription" RPC defined in [RFC8639] MUST include a list of Message
   Generator IDs to indicate how the Global Subscription is decomposed
   into several Component Subscriptions.

   The "subscription-started" and "subscription-modified" notification
   defined in [RFC8639] MUST also include a list of Message Generator
   IDs to notify the current Publishers for the corresponding Global
   Subscription.

7.  Subscription State Change Notifications

   In addition to sending event records to receivers, the Master MUST
   also send subscription state change notifications [RFC8639] when
   events related to subscription management have occurred.  All the
   subscription state change notifications MUST be delivered by the
   Master.

   When the subscription decomposition result changed, the
   "subscription-modified" notification MUST be sent to indicate the new
   list of Publishers.

8.  Publisher Configurations

   This document assumes all the Publishers are preconfigured to be able
   to push data.  The actual working Publishers are selected dynamically
   based on the subscription decomposition result.  For UDP Publishers,
   the virtual IP address could be assigned for the publication.  So all
   the UDP Publishers on the device can use the same source IP address
   configured, which may even not routeable.  For connection based
   Publishers, e.g., HTTPS-based transport
   [I-D.ietf-netconf-https-notif], each Publisher MUST be able to
   receive packets from the receivers.  This document does not restrict
   the way how the Publishers are accessible.

   The specific configuration on transports is out of the scope of this
   document.

9.  YANG Tree












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   module: ietf-multiple-stream-originators
     augment /sn:subscriptions/sn:subscription:
       +--ro message-generator-id*   string
     augment /sn:subscription-started:
       +--ro message-generator-id*   string
     augment /sn:subscription-modified:
       +--ro message-generator-id*   string
     augment /sn:establish-subscription/sn:output:
       +--ro message-generator-id*   string

10.  YANG Module

 <CODE BEGINS> file "ietf-multiple-stream-originators@2019-10-12.yang"
 module ietf-multiple-stream-originators {
   yang-version 1.1;
   namespace
     "urn:ietf:params:xml:ns:yang:ietf-multiple-stream-originators";
   prefix mso;
   import ietf-subscribed-notifications {
     prefix sn;
   }

   organization "IETF NETCONF (Network Configuration) Working Group";
   contact
     "WG Web:   <http:/tools.ietf.org/wg/netconf/>
      WG List:  <mailto:netconf@ietf.org>

      Editor:   Tianran Zhou
                <mailto:zhoutianran@huawei.com>

      Editor:   Guangying Zheng
                <mailto:zhengguangying@huawei.com>";


   description
     "Defines augmentation for ietf-subscribed-notifications to enable
      the distributed publication with single subscription.

     Copyright (c) 2018 IETF Trust and the persons identified as authors
     of the code.  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
     (https://trustee.ietf.org/license-info).

     This version of this YANG module is part of RFC XXXX; see the RFC



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     itself for full legal notices.";

   revision 2019-10-12 {
     description
       "Initial version";
     reference
       "RFC XXXX: Subscription to Multiple Stream Originators";
   }

   grouping message-generator-ids {
     description
       "Provides a reusable list of message-generator-ids.";

     leaf-list message-generator-id {
       type string;
       config false;
       ordered-by user;
       description
         "Software entity which created the message (e.g.,
          linecard 1). This field is used to notify the
          collector the working originator.";
     }
   }

   augment "/sn:subscriptions/sn:subscription" {
     description
       "This augmentation allows the message generators to be exposed
        for a subscription.";

     uses message-generator-ids;
   }

   augment "/sn:subscription-started" {
     description
       "This augmentation allows MSO specific parameters to be
        exposed for a subscription.";

     uses message-generator-ids;
   }

   augment "/sn:subscription-modified" {
     description
       "This augmentation allows MSO specific parameters to be
        exposed for a subscription.";

     uses message-generator-ids;
   }




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   augment "/sn:establish-subscription/sn:output" {
     description
       "This augmentation allows MSO specific parameters to be
        exposed for a subscription.";

     uses message-generator-ids;
   }
 }
 <CODE ENDS>

11.  IANA Considerations

   This document registers the following namespace URI in the IETF XML
   Registry [RFC3688]:

      URI: urn:ietf:params:xml:ns:yang:ietf-multiple-stream-originators

      Registrant Contact: The IESG.

      XML: N/A; the requested URI is an XML namespace.

   This document registers the following YANG module in the YANG Module
   Names registry [RFC3688]:

      Name: ietf-multiple-stream-originators

      Namespace: urn:ietf:params:xml:ns:yang:ietf-multiple-stream-
      originators

      Prefix: mso

      Reference: RFC XXXX

12.  Transport Considerations

   The distributed data export mechanism enabled by this draft is
   expected to generate more data than YANG-Push [RFC8641].  The large
   amount of data may congest the network and impact other network
   business.  In this case, the collector may also not be able to accept
   all the data.  So the congestion control method is required for any
   transport that is going to implement the solution proposed in this
   document.

13.  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



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   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
   [RFC5246].

   The NETCONF Access Control Model (NACM) [RFC6536] 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.

   The new data nodes introduced in this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control read access (e.g., via get-config or
   notification) to this data nodes.  These are the subtrees and data
   nodes and their sensitivity/vulnerability:

   o  /subscriptions/subscription/message-generator-ids

   The entries in the two lists above will show where subscribed
   resources might be located on the publishers.  Access control MUST be
   set so that only someone with proper access permissions has the
   ability to access this resource.

   Other Security Considerations is the same as those discussed in YANG-
   Push [RFC8641].

14.  Acknowledgements

   We thank Kent Watsen, Mahesh Jethanandani, Martin Bjorklund, Tim
   Carey and Qin Wu for their constructive suggestions for improving
   this document.

15.  References

15.1.  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>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.







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   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

   [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>.

   [RFC6536]  Bierman, A. and M. Bjorklund, "Network Configuration
              Protocol (NETCONF) Access Control Model", RFC 6536,
              DOI 10.17487/RFC6536, March 2012,
              <https://www.rfc-editor.org/info/rfc6536>.

   [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>.

   [RFC8639]  Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard,
              E., and A. Tripathy, "Subscription to YANG Notifications",
              RFC 8639, DOI 10.17487/RFC8639, September 2019,
              <https://www.rfc-editor.org/info/rfc8639>.

   [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>.

15.2.  Informative References

   [I-D.ietf-netconf-https-notif]
              Jethanandani, M. and K. Watsen, "An HTTPS-based Transport
              for Configured Subscriptions", draft-ietf-netconf-https-
              notif-01 (work in progress), October 2019.

   [I-D.ietf-netconf-notification-messages]
              Voit, E., Birkholz, H., Bierman, A., Clemm, A., and T.
              Jenkins, "Notification Message Headers and Bundles",
              draft-ietf-netconf-notification-messages-07 (work in
              progress), August 2019.







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Appendix A.  Examples

   This appendix is non-normative.

A.1.  Dynamic Subscription

   Figure 3 shows a typical dynamic subscription to the device with
   distributed data export capability.

   +-------------+                 +-------------+ +-------------+
   | Subscriber/ |                 |  Publisher  | |  Publisher  |
   | Receiver    |                 |  (Master)   | |  (Agent)    |
   +-------------+                 +------+------+ +------+------+
          |                               |               |
          | establish-subscription        |               |
          +------------------------------>+ component     |
          |                               | subscription  |
          | RPC Reply: OK, id #22         +-------------->+
          | message generator ID [#1, #2] |               |
          +<------------------------------+               |
          |                               |               |
          | notif-mesg, id #22            |               |
          | message generator ID #1       |               |
          +<------------------------------+               |
          |                               |               |
          | notif-mesg, id#22             |               |
          | message generator ID #2       |               |
          +<----------------------------------------------+
          |                               |               |
          | modify-subscription (id#22)   |               |
          +------------------------------>+ component     |
          |                               | subscription  |
          | RPC Reply: OK, id #22         +-------------->+
          +<------------------------------+               |
          |                               |               |
          | subscription-modified, id#22  |               |
          | message generator ID [#1]     |               |
          +<------------------------------+               |
          |                               |               |
          | notif-mesg, id #22            |               |
          | message generator ID #1       |               |
          +<------------------------------+               |
          |                               |               |
          |                               |               |
          +                               +               +

                 Fig. 3 Call Flow for Dynamic Subscription




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   A "establish-subscription" RPC request as per [RFC8641] is sent to
   the Master with a successful response.  An example of using NETCONF
   might look like:

 <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>
     <yp:periodic>
       <yp:period>500</yp:period>
     </yp:periodic>
   </establish-subscription>
 </netconf:rpc>

                  Fig. 4 "establish-subscription" Request

   As the device is able to fully satisfy the request, the request is
   given a subscription ID of 22.  The response as in Figure 5 indicates
   that the subscription is decomposed into two component subscriptions
   which will be published by two message generators: #1 and #2.

<rpc-reply message-id="101"
   xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
   <id
    xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
      22
   </id>
   <message-generator-id
    xmlns="urn:ietf:params:xml:ns:yang:ietf-multiple-stream-originators>
      1
   </message-generator-id>
   <message-generator-id
    xmlns="urn:ietf:params:xml:ns:yang:ietf-multiple-stream-originators>
      2
   </message-generator-id>
</rpc-reply>

           Fig. 5 "establish-subscription" Positive RPC Response




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   Then, both Publishers send notifications with the corresponding piece
   of data to the receiver.

   The subscriber may invoke the "modify-subscription" RPC for a
   subscription it previously established.  The RPC has no difference to
   the single publisher case as in [RFC8641].  Figure 6 provides an
   example where a subscriber attempts to modify the period and
   datastore XPath filter of a subscription using NETCONF.

     <rpc message-id="102"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <modify-subscription
           xmlns=
             "urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
           xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
         <id>22</id>
         <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:bar
         </yp:datastore-xpath-filter>
         <yp:periodic>
           <yp:period>250</yp:period>
         </yp:periodic>
        </modify-subscription>
     </rpc>

                   Fig. 6 "modify-subscription" Request

   If the modification is successfully accepted, the "subscription-
   modified" subscription state notification is sent to the subscriber
   by the Master.  The notification, Figure 7 for example, indicates the
   modified subscription is decomposed into one component subscription
   which will be published by message generator #1.














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<notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
  <eventTime>2007-09-01T10:00:00Z</eventTime>
  <subscription-modified
      xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
      xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
    <id>22</id>
    <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:bar
    </yp:datastore-xpath-filter>
    <yp:periodic>
        <yp:period>250</yp:period>
    </yp:periodic>
    <message-generator-id
    xmlns="urn:ietf:params:xml:ns:yang:ietf-multiple-stream-originators>
       1
    </message-generator-id>
  </subscription-modified>
</notification>

      Fig. 7 "subscription-modified" Subscription State Notification

A.2.  Configured Subscription

   Figure 8 shows a typical configured subscription to the device with
   distributed data export capability.





















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   +-------------+                 +-------------+ +-------------+
   | Receiver    |                 |  Publisher  | |  Publisher  |
   |             |                 |  (Master)   | |  (Agent)    |
   +------+------+                 +------+------+ +------+------+
          |                               |               |
          | subscription-started, id#39   |               |
          | message generator ID [#1, #2] |               |
          +<------------------------------+               |
          |                               |               |
          | notif-mesg, id#39             |               |
          | message generator ID #1       |               |
          +<------------------------------+               |
          |                               |               |
          | notif-mesg, id#39             |               |
          | message generator ID #2       |               |
          +<----------------------------------------------+
          |                               |               |
          |                               |               |
          |                               |               |

               Fig. 8 Call Flow for Configured Subscription

   Before starting to push data, the "subscription-started" subscription
   state notification is sent to the receiver.  The following example
   assumes the NETCONF transport has already established.  The
   notification indicates that the configured subscription is decomposed
   into two component subscriptions which will be published by two
   message generators: #1 and #2.























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<notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
  <eventTime>2007-09-01T10:00:00Z</eventTime>
  <subscription-started
      xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
      xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
    <identifier>39</identifier>
    <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>
    <yp:periodic>
        <yp:period>250</yp:period>
    </yp:periodic>
    <message-generator-id
    xmlns="urn:ietf:params:xml:ns:yang:ietf-multiple-stream-originators>
       1
    </message-generator-id>
    <message-generator-id
    xmlns="urn:ietf:params:xml:ns:yang:ietf-multiple-stream-originators>
       2
    </message-generator-id>
  </subscription-started>
</notification>

       Fig. 9 "subscription-started" Subscription State Notification

   Then, both Publishers send notifications with the corresponding piece
   of data to the receiver.

Appendix B.  Change Log

   (To be removed by RFC editor prior to publication)

   v01

   o  Minor revision on Subscription Decomposition

   o  Revised terminologies

   o  Removed most implementation related text

   o  Place holder of two sections: Subscription Management, and
      Notifications on Subscription State Changes




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   v02

   o  Revised section 4 and 5.  Moved them from apendix to the main
      text.

   v03

   o  Added a section for Terminologies.

   o  Added a section for Subscription State Change Notifications.

   o  Improved the Publication Composition section by adding a method to
      check the integrity of the data generated from different
      Publishers at the same time period.

   o  Revised the solution overview for a more clear description.

   v04

   o  Added the YANG data model for the proposed augment.

   v05

   o  Added the IANA considerations, transport considerations and
      security considerations.

   v06

   o  Added examples.

   v07

   o  Removed the IoT use case.

   o  Revised examples.

   o  Add discussion on Publisher Configurations in section 8.

   v08

   o  Cleared up the document to fix Terms, nits.

   o  Reduced internal implementation descriptions.

   o  Clarified Message Generator ID.






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Authors' Addresses

   Tianran Zhou
   Huawei
   156 Beiqing Rd., Haidian District
   Beijing
   China

   Email: zhoutianran@huawei.com


   Guangying Zheng
   Huawei
   101 Yu-Hua-Tai Software Road
   Nanjing, Jiangsu
   China

   Email: zhengguangying@huawei.com


   Eric Voit
   Cisco Systems
   United States of America

   Email: evoit@cisco.com


   Alexander Clemm
   Futurewai
   2330 Central Expressway
   Santa Clara, California
   United States of America

   Email: ludwig@clemm.org

















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