Notification Message Headers and Bundles
draft-ietf-netconf-notification-messages-02

NETCONF                                                          E. Voit
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                              A. Bierman
Expires: April 2, 2018                                         YumaWorks
                                                                A. Clemm
                                                                  Huawei
                                                              T. Jenkins
                                                           Cisco Systems
                                                      September 29, 2017


                Notification Message Headers and Bundles
              draft-ietf-netconf-notification-messages-01

Abstract

   This document defines a new notification message format, using yang-
   data.  Included are:

   o  a new notification mechanism and encoding to replace the one way
      operation of RFC-5277

   o  a set of common, transport agnostic message header objects.

   o  how to bundle multiple event records into a single notification
      message.

   o  how to ensure these new capabilities are only used with capable
      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 April 2, 2018.





Voit, et al.              Expires April 2, 2018                 [Page 1]


Internet-Draft                Notifications               September 2017


Copyright Notice

   Copyright (c) 2017 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.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Header Objects  . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Encapsulation of Header Objects in Messages . . . . . . . . .   4
     4.1.  One Notification per Message  . . . . . . . . . . . . . .   5
     4.2.  Many Notifications per Message  . . . . . . . . . . . . .   6
     4.3.  Notification Type in Payload  . . . . . . . . . . . . . .   9
   5.  Configuration of Headers  . . . . . . . . . . . . . . . . . .   9
   6.  Discovering Receiver Support  . . . . . . . . . . . . . . . .  10
   7.  YANG Module . . . . . . . . . . . . . . . . . . . . . . . . .  11
   8.  Backwards Compatibility . . . . . . . . . . . . . . . . . . .  17
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  18
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  18
     11.2.  Informative References . . . . . . . . . . . . . . . . .  18
   Appendix A.  Changes between revisions  . . . . . . . . . . . . .  19
   Appendix B.  Issues being worked  . . . . . . . . . . . . . . . .  19
   Appendix C.  Subscription Specific Headers  . . . . . . . . . . .  20
   Appendix D.  Implications to Existing RFCs  . . . . . . . . . . .  20
     D.1.  Implications to RFC-7950  . . . . . . . . . . . . . . . .  20
     D.2.  Implications to RFC-8040  . . . . . . . . . . . . . . . .  21
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21

1.  Introduction

   Mechanisms to support subscription to event notifications and yang
   datastore push are being defined in [subscribe] and [yang-push].
   Work on those documents has shown that notifications described in
   [RFC7950] section 7.16 could benefit from transport independent
   headers.  Communicating the following information to receiving



Voit, et al.              Expires April 2, 2018                 [Page 2]


Internet-Draft                Notifications               September 2017


   applications can be done without explicit linkage to an underlying
   transport protocol:

   o  the time information was generated

   o  the time the information was sent

   o  a signature to verify authenticity

   o  the process generating the information

   o  an originating request correlation

   o  an ability to bundle information records into one a message

   o  the ability to check for message loss/reordering

   The document describes information elements needed for the functions
   above.  It also provides YANG structures for sending messages
   containing one or more events and/or update records to a receiver.

2.  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.

   The definition of notification is in RFC 7950 [RFC7950].  Publisher,
   receiver, and subscription are defined in [subscribe].

3.  Header Objects

   There are a number of transport independent headers which should have
   common definition.  These include:

   o  subscription-id: provides a reference into the reason the
      publisher believed the receiver wishes to be notified of this
      specific information.

   o  notification-time: the time an event, datastore update, or other
      item is recognized and recorded within the publisher.

   o  notification-id: Identifies the name of the notification, per the
      YANG notification statement.  May also provide the name of a yang-
      data statement (wheterh this is in scope is tbd).




Voit, et al.              Expires April 2, 2018                 [Page 3]


Internet-Draft                Notifications               September 2017


   o  observation-domain-id: identifies the publisher process which
      discovered and recorded the event notification. (note: look to
      reuse the domains set up with IPFIX.)

   o  message-time: the time the message was packaged sent to the
      transport layer for delivery to the receiver.

   o  signature: allows an application to sign a message so that a
      receiver can verify the authenticity of the message.

   o  message-id: for a specific message generator, this identifies a
      message which includes one or more event records.

   o  previous-message-id: the message-id of the message preceding the
      current one intended for the same receiver.  When used in
      conjunction with the current message-id, this allows loss/
      duplication across previous messages to be discovered.  If there
      was no previous message from a message generator, the reserved id
      "0" must be sent.

   o  message-generator-id: identifier for the process which created the
      message.  This allows disambiguation of an information source,
      such as the identification of different line cards sending the
      messages.  Used in conjunction with previous-message-id, this can
      help find drops and duplications when messages are coming from
      multiple sources on a device.  If there is a message-generator-id
      in the header, then the previous-message-id MUST be the message-id
      from the last time that message-generator-id was sent.

4.  Encapsulation of Header Objects in Messages

   A specific set of well-known objects are of potential use to
   networking layers prior being interpreted by some receiving
   application layer process.  By exposing this object information as
   part of a header, and by using standardized object names, it becomes
   possible for this object information to be leveraged in transit.

   The objects defined in the previous section are these well-known
   header objects.  These objects are identified within a dedicated
   header subtree which leads off a particular transportable message.
   This allows header objects to be easily be decoupled, stripped, and
   processed separately.

   There are two types of transportable messages: one format is used
   when there is one notification being encapsulated, and another format
   used when there are many notifications being bundled into one
   message.




Voit, et al.              Expires April 2, 2018                 [Page 4]


Internet-Draft                Notifications               September 2017


   A receiver which supporting this document MUST be able to handle
   receipt of either type of message from an publisher.  It is possible
   that changes between message types can occur without any prior
   indication.

4.1.  One Notification per Message

   Below are contents of a message when there is only one notification
   in an encapsulated and encoded message:

       yang-data message
          +-- message-header
          |  +-- notification-time           yang:date-and-time
          |  +-- subscription-id*            uint32
          |  +-- notification-id?            uint32
          |  +-- observation-domain-id?      string
          |  +-- message-id?                 uint32
          |  +-- message-time?               yang:date-and-time
          |  +-- previous-message-id?        uint32
          |  +-- message-generator-id?       string
          |  +-- signature?                  string
          +-- receiver-record-contents?

   An actual instance of such a message when encoded in XML might look
   like:


























Voit, et al.              Expires April 2, 2018                 [Page 5]


Internet-Draft                Notifications               September 2017


   <yang-data message
     xmlns="urn:ietf:params:xml:ns:yang:ietf-notification-messages:1.0">
     <message-header>
       <notification-time>
             2017-02-14T00:00:02Z
       </notification-time>
       <subscription-id>
             823472
       </subscription-id>
       <message-time>
             2017-02-14T00:00:05Z
       </message-time>
       <message-id>
             456
       </message-id>
       <previous-message-id>
             567
       </previous-message-id>
       <signature>
             lKIo8s03fd23.....
       </signature>
     </message-header>
     <push-change-update xmlns=
         "urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
       <datastore-changes-xml>
         <alpha xmlns="http://example.com/sample-data/1.0" >
           <beta urn:ietf:params:xml:ns:netconf:base:1.0:
                operation="delete"/>
         </alpha>
       </datastore-changes-xml>
     </push-change-update>
   </yang-data>

4.2.  Many Notifications per Message

   In many implementations, it may be inefficient to transport every
   notification independently.  Instead, scale and processing speed can
   be improved by placing multiple notifications into one transportable
   bundle.

   When this is done, one additional header field becomes valuable.
   This is the "notification-count" which would tally the quantity of
   records which make up the contents of the bundle.  It is true that
   the record count can be derived, but early access to this information
   could change receiver processing.

   The format of a bundle would look as below.  When compared to the
   unbundled notification, note that the headers have been split so that



Voit, et al.              Expires April 2, 2018                 [Page 6]


Internet-Draft                Notifications               September 2017


   one set of headers associated with the notification occur once at the
   beginning of the message, and additional record specific headers
   which occur before individual records.

       yang-data bundled-message
          +-- bundled-message-header
          |  +-- message-time                yang:date-and-time
          |  +-- message-id?                 uint32
          |  +-- previous-message-id?        uint32
          |  +-- message-generator-id?       string
          |  +-- signature?                  string
          |  +-- notification-count?         uint16
          +-- notifications*
             +-- notification-header
             |  +-- notification-time        yang:date-and-time
             |  +-- subscription-id*         uint32
             |  +-- notification-id?         uint32
             |  +-- observation-domain-id?   string
             +-- receiver-record-contents?

   An actual instance of a bundled notification might look like:






























Voit, et al.              Expires April 2, 2018                 [Page 7]


Internet-Draft                Notifications               September 2017


   <yang-data bundled-message
     xmlns="urn:ietf:params:xml:ns:yang:ietf-notification-messages:1.0">
     <bundled-message-header>
       <message-time>
             2017-02-14T00:00:05Z
       </message-time>
       <message-id>
             456
       </message-id>
       <previous-message-id>
             567
       </previous-message-id>
       <signature>
             lKIo8s03fd23...
       </signature>
       <notification-count>
             2
       </notification-count>
     </bundled-message-header>
     <notifications>
       <notification>
         <notification-header>
           <notification-time>
               2017-02-14T00:00:02Z
           </notification-time>
           <subscription-id>
               823472
           </subscription-id>
         </notification-header>
         <push-change-update xmlns=
           "urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
           <datastore-changes-xml>
             <alpha xmlns="http://example.com/sample-data/1.0">
                <beta urn:ietf:params:xml:ns:netconf:base:1.0:
                    operation="delete"/>
             </alpha>
           </datastore-changes-xml>
         </push-change-update>
       </notification>
       <notification>
             ...(record #2)...
       </notification>
     </notifications>
   </yang-data>







Voit, et al.              Expires April 2, 2018                 [Page 8]


Internet-Draft                Notifications               September 2017


4.3.  Notification Type in Payload

   The type of notification transported within a record could be a
   header.  However the notification name and namespace is the first
   element in the receiver record contents payload.  As this can be
   determined by the YANG module containing the notification-stmt as
   represented within the first part of the encapsulated notification
   message, this information need not replicated within a header.

5.  Configuration of Headers

   A publisher MUST select the set of headers to use for a particular
   message.  The two mandatory headers which MUST always be applied to
   every message are 'message-time' and 'subscription-id'

   Beyond these two mandatory headers, the following are additional
   sources which can add common headers to a message.

   1.  Publisher wide default headers for all notifications.  These are
       included if a common header is inserted into 'additional-headers'
       shown in the figure below.

   2.  More notification specific headers may also be desired.  If new
       headers are needed for a specific notification in the YANG model,
       this can be populated through 'per-notification-headers'.

   3.  An application process may also identify common headers to use
       when transporting notifications for a specific subscription.  How
       these are identified to a publisher is out-of-scope.

   The set of headers used for any particular message is the superset of
   headers for the items listed above.

   The YANG tree showing elements of configuration is depicted in the
   following figure.

   module: ietf-notification-messages
       +--rw additional-default-headers    {publisher}?
          +--rw additional-headers*            common-header
          +--rw notification-specific-default* [module notification]
             +--rw module                      yang:yang-identifier
             +--rw notification                string
             +--rw per-notification-headers*   common-header

                       Configuration Model structure

   Of note in this tree is the optional feature of 'publisher'.  This
   feature indicates an ability to send notifications.  A publisher



Voit, et al.              Expires April 2, 2018                 [Page 9]


Internet-Draft                Notifications               September 2017


   supporting this specification MUST also be able to parse any messages
   received as defined in this document.

6.  Discovering Receiver Support

   We need capability exchange from the receiver to the publisher at
   transport session initiation to indicate support for this
   specification.

   For all types of transport connections, if the receiver indicates
   support for this specification, then it MAY be used.  In addition,
   [RFC5277] one-way notifications MUST NOT be used if the receiver
   indicates support for this specification to a publisher which also
   supports it.

   Where NETCONF transport is used, advertising this specification's
   namespace during an earlier client capabilities discovery phase MAY
   be used to indicate support for this specification:

      <hello xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
        <capabilities>
          <capability>
            urn:ietf:params:xml:ns:yang:ietf-notification-messages:1.0
          </capability>
        </capabilities>
        <session-id>4</session-id>
      </hello>

   NOTE: It is understood that even though it is allowed in [RFC6241]
   section 8.1, robust NETCONF client driven capabilities exchange is
   not something which is common in implementation.  Therefore reviewers
   are asked to submit alternative proposals to the mailing list.

   For RESTCONF, a mechanism for capability discovery is TBD.  Proposals
   are also welcome here.

   The mechanism described above assumes that a capability discovery
   phase happens before a subscription is started.  This is not always
   the case.  As an example, consider HTTP2 configured subscriptions
   from section 3.1.3 of [http-push], there is no guarantee that a
   capability exchange has taken place before the updates are pushed.  A
   solution for this could be that a receiver would reply "ok" and reply
   with the client capabilities as part of the POST.  (Or just use a
   different HTTP status code like 202 instead of 200 'ok').  As such a
   requirement creates a new dependency for [http-push] upon this
   specification, more discussion is required to decide if this is a
   viable solution.




Voit, et al.              Expires April 2, 2018                [Page 10]


Internet-Draft                Notifications               September 2017


7.  YANG Module

<CODE BEGINS> file "ietf-notification-messages.yang"
module ietf-notification-messages {
  yang-version 1.1;
  namespace
     "urn:ietf:params:xml:ns:yang:ietf-notification-messages";
  prefix nm;

  import ietf-yang-types { prefix yang; }
  import ietf-restconf   { prefix rc;   }


  organization "IETF";
  contact
    "WG Web:   <http://tools.ietf.org/wg/netconf/>
     WG List:  <mailto:netconf@ietf.org>

     Editor:   Eric Voit
               <mailto:evoit@cisco.com>

     Editor:   Alexander Clemm
               <mailto:ludwig@clemm.org>

     Editor:   Andy Bierman
               <mailto:andy@yumaworks.com>

     Editor:   Tim Jenkins
               <mailto:timjenki@cisco.com>";

  description
    "This module contains conceptual YANG specifications for yang-data
    messages carrying notifications with well known header objects.";

  revision 2017-09-28 {
    description
      "Initial version.";

    reference
      "draft-ietf-netconf-notification-messages-01";
  }

 /*
  * FEATURES
  */

  feature publisher {
    description



Voit, et al.              Expires April 2, 2018                [Page 11]


Internet-Draft                Notifications               September 2017


      "This feature indicates that support for both publisher and
      receiver of messages complying to the specification.";
  }

  /*
   * IDENTITIES
   */

   /* Identities for common headers */

  identity common-header {
    description
      "A well known header which can be included somewhere within a
      message.";
  }

  identity notification-time  {
    base common-header;
    description
      "Header information consisting of the time an originating process
      created the notification or yang-data.";
  }

  identity notification-id {
    base common-header;
    description
      "Header information consisting of an identifier for the
      notification or yang-data record. ";
  }

  identity subscription-id {
    base common-header;
    description
      "Header information consisting of the identifier of the
      subscription associated with the notification or yang-data being
      encapsulated.";
  }

  identity observation-domain-id {
    base common-header;
    description
      "Header information identifying the software entity which created
      the notification or yang-data (e.g., process id).";
  }

  identity message-id {
    base common-header;
    description



Voit, et al.              Expires April 2, 2018                [Page 12]


Internet-Draft                Notifications               September 2017


      "Header information that identifies a message to a specific
      receiver";
  }

  identity message-time {
    base common-header;
    description
      "Header information consisting of time the message headers were
      placed generated prior to being sent to transport";
  }

  identity previous-message-id {
    base common-header;
    description
      "Header information consisting of a message id previously sent by
      the publisher to a specific receiver (allows detection of
      loss/duplication).";
  }

  identity message-generator-id {
    base common-header;
    description
      "Header information consisting of an identifier for a software
      entity which created the message (e.g., linecard 1).";
  }

  identity signature {
    base common-header;
    description
      "Header information consisting of a signature on the contents of
      a message.  This can be useful for originating applications to
      verify record contents even when shipping over unsecure
      transport.";
  }

  identity notification-count {
    base common-header;
    description
      "Header information consisting of the quantity of notifications in
      a bundled-message for a specific receiver.";
  }

  /*
   * TYPEDEFs
   */

  typedef common-header {
    type identityref {



Voit, et al.              Expires April 2, 2018                [Page 13]


Internet-Draft                Notifications               September 2017


      base common-header;
    }
    description
      "Type of header object which may be included somewhere within a
      message.";
  }

  /*
   * GROUPINGS
   */

  grouping message-header {
    description
      "Header information included with a message.";
    leaf message-id {
      type uint32;
      description
        "Unique id for a message going to a receiver.";
    }
    leaf message-time {
      type yang:date-and-time;
      description
        "time the message was generated prior to being sent to
        transport.";
    }
    leaf previous-message-id {
      type uint32;
      description
        "message id previously sent by publisher to a specific
        receiver (allows detection of loss/duplication).";
    }
    leaf message-generator-id {
      type string;
      description
        "Software entity which created the message (e.g., linecard 1).";
    }
    leaf signature {
      type string;
      description
        "Any originator signing of the contents of a message.  This can
        be useful for originating applications to verify record contents
        even when shipping over unsecure transport.";
    }
  }

  grouping notification-header {
    description
      "Common informational objects which might help a receiver



Voit, et al.              Expires April 2, 2018                [Page 14]


Internet-Draft                Notifications               September 2017


      interpret the meaning, details, or importance of a notification.";
    leaf notification-time {
      type yang:date-and-time;
      mandatory true;
      description
        "Time the system recognized the occurrence of an event.";
    }
    leaf-list subscription-id {
      type uint32;
      description
        "Id of the subscription which led to the notification being
        generated.";
    }
    leaf notification-id {
      type uint32;
      description
        "Identifier for the notification record.";
    }
    leaf observation-domain-id {
      type string;
      description
        "Software entity which created the notification record (e.g.,
        process id).";
    }
  }

  /*
   * YANG-DATA messages for receivers
   */

 /* Message to a receiver containing one notification.*/
  rc:yang-data message {
    container message-header {
      description
        "delineates header info from content for easy parsing.";
      uses notification-header;
      uses message-header;
    }
    anydata notification-contents {
      description
        "Non-header info of what actually got sent to receiver.  This
        includes after any content based security filtering.  Need to
        determine if/how it is viable not to include tag encapsulation
        for this object.";
    }
  }

  /* Message to a receiver containing many bundled notifications.*/



Voit, et al.              Expires April 2, 2018                [Page 15]


Internet-Draft                Notifications               September 2017


  rc:yang-data bundled-message {
    container bundled-message-header {
        description
            "Header info for messages.";
        uses message-header {
          refine message-time {
            mandatory true;
          }
        }
        leaf notification-count {
            type uint16;
            description
                "Quantity of notification records in a bundled-message
                specific receiver.";
        }
    }
    list notifications {
      description
        "Set of notifications to a receiver.";
      container notification-header {
        description
          "Header info for each bundled notification.";
        uses notification-header;
      }
      anydata notification-contents {
        description
        "Non-header info of what actually got sent to receiver.  This
        includes after any content based security filtering.  Need to
        determine if/how it is viable not to include tag encapsulation
        for this object.";
      }
    }
  }

  /*
   * DATA-NODES
   */

  container additional-default-headers {
    if-feature "publisher";
    description
      "This container maintains a list of which additional notifications
      should use which common headers if the receiver supports this
      specification.  The name starts with additional because there are
      some mandatory common headers not listed in the container.  These
      headers are (1) message-time and (2) subscription-id.";
    leaf-list additional-headers {
      type common-header;



Voit, et al.              Expires April 2, 2018                [Page 16]


Internet-Draft                Notifications               September 2017


      description
        "This list contains the additional default headers which are to
        be applied to each message from this publisher.";
    }
    list notification-specific-default {
      key "module notification";
      description
        "For any included notification, this list provides additional
        common headers.";
      leaf module {
       type yang:yang-identifier;
       description
         "Name of the module containing a notification.";
       }
      leaf notification {
         type string {
           pattern 'notification $|yang-data $';
         }
         description
           "The name of the notification or yang-data being sent.";
      }
      leaf-list per-notification-headers {
         type common-header;
         description
           "The set of additional default headers for a specific
           notification.";
      }
    }
  }
}
<CODE ENDS>

8.  Backwards Compatibility

   With this specification, there is no change to YANG's 'notification'
   statement

   Legacy clients are unaffected, and existing users of [RFC5277],
   [RFC7950], and [RFC8040] are free to use current behaviors until all
   involved device support this specification.

9.  Security Considerations

   Certain headers might be computationally complex for a publisher to
   deliver.  Signatures or encryption are two examples of this.  It MUST
   be possible to suspend or terminate a subscription due to lack of
   resources based on this reason.




Voit, et al.              Expires April 2, 2018                [Page 17]


Internet-Draft                Notifications               September 2017


   Decisions on whether to bundle or not to a receiver are fully under
   the purview of the Publisher.  A receiver could slow delivery to
   existing subscriptions by creating new ones.  (Which would result in
   the publisher going into a bundling mode.)

10.  Acknowledgments

   For their valuable comments, discussions, and feedback, we wish to
   acknowledge Martin Bjorklund and Kent Watsen.

11.  References

11.1.  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>.

   [RFC5277]  Chisholm, S. and H. Trevino, "NETCONF Event
              Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008,
              <https://www.rfc-editor.org/info/rfc5277>.

   [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>.

   [subscribe]
              Voit, E., Clemm, A., Gonzalez Prieto, A., Prasad Tripathy,
              A., and E. Nilsen-Nygaard, "Custom Subscription to Event
              Notifications", September 2017,
              <https://datatracker.ietf.org/doc/
              draft-ietf-netconf-subscribed-notifications/>.

11.2.  Informative References

   [http-push]
              Voit, Eric., Clemm, Alexander., Tripathy, A., Nilsen-
              Nygaard, E., and Alberto. Gonzalez Prieto, "Restconf and
              HTTP transport for event notifications", August 2016,
              <https://datatracker.ietf.org/doc/
              draft-ietf-netconf-restconf-notif/>.

   [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>.




Voit, et al.              Expires April 2, 2018                [Page 18]


Internet-Draft                Notifications               September 2017


   [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>.

   [yang-push]
              Clemm, A., Voit, E., Gonzalez Prieto, A., Prasad Tripathy,
              A., and E. Nilsen-Nygaard, "Subscribing to YANG datastore
              push updates", April 2017,
              <https://datatracker.ietf.org/doc/
              draft-ietf-netconf-yang-push/>.

Appendix A.  Changes between revisions

   (To be removed by RFC editor prior to publication)

   v00 - v01

   o  Alternative to 5277 one-way notification added

   o  Storage of default headers by notification type

   o  Backwards compatibility

   o  Capability discovery

   o  Move to yang-data

   o  Removed dscp and record-type as common headers.  (Record type can
      be determined by the namespace of the record contents.  Dscp is
      useful where applications need internal communications within a
      Publisher, but it is unclear as to whether this use case need be
      exposed to a receiver.

Appendix B.  Issues being worked

   (To be removed by RFC editor prior to publication)

   Is this capability just for notifications, or is it for any yang-data
   element too?

   Improved discovery mechanisms for NETCONF

   Do we want to have additional headers for a specific notification?
   Right now this is included, but it could be excluded.



Voit, et al.              Expires April 2, 2018                [Page 19]


Internet-Draft                Notifications               September 2017


   Should we defer support for HTTP2 configured subscriptions until this
   draft is available?  Without capabilities exchange, it might just be
   easier to wait.

   Encoding of notification-contents so that individual notification
   framing isn't needed.

   We need to link to Andy Bierman's anydata extensibility draft.

Appendix C.  Subscription Specific Headers

   (To be removed by RFC editor prior to publication)

   This section discusses a future functional addition which could
   leverage this draft.  It is included for informational purposes only.

   A dynamic subscriber might want to mandate that certain headers be
   used for push updates from a publisher.  Some examples of this
   include a subscriber requesting to:

   o  establish this subscription, but just if transport messages
      containing the pushed data will be encrypted,

   o  establish this subscription, but only if you can attest to the
      information being delivered in requested notification records, or

   o  provide a sequence-id for all messages to this receiver (in order
      to check for loss).

   Providing this type of functionality would necessitate a new revision
   of the [subscribe]'s RPCs and state change notifications.
   Subscription specific header information would overwrite the default
   headers identified in this document.

Appendix D.  Implications to Existing RFCs

   (To be removed by RFC editor prior to publication)

   YANG one-way exchanges currently use a non-extensible header and
   encoding defined in section 4 of RFC-5277.  These RFCs MUST be
   updated to enable this draft.  These RFCs SHOULD be updated to
   provide examples

D.1.  Implications to RFC-7950

   Sections which expose netconf:capability:notification:1.0 are 4.2.10





Voit, et al.              Expires April 2, 2018                [Page 20]


Internet-Draft                Notifications               September 2017


   Sections which provide examples using netconf:notification:1.0 are
   7.10.4, 7.16.3, and 9.9.6

D.2.  Implications to RFC-8040

   Section 6.4 demands use of RFC-5277's netconf:notification:1.0, and
   later in the section provides an example.

Authors' Addresses

   Eric Voit
   Cisco Systems

   Email: evoit@cisco.com


   Andy Bierman
   YumaWorks

   Email: andy@yumaworks.com


   Alexander Clemm
   Huawei

   Email: ludwig@clemm.org


   Tim Jenkins
   Cisco Systems

   Email: timjenki@cisco.com



















Voit, et al.              Expires April 2, 2018                [Page 21]