draft-ietf-netconf-udp-notif-12.txt

NETCONF                                                         G. Zheng
Internet-Draft                                                   T. Zhou
Intended status: Standards Track                                  Huawei
Expires: 25 July 2024                                            T. Graf
                                                                Swisscom
                                                             P. Francois
                                                           A. Huang Feng
                                                               INSA-Lyon
                                                              P. Lucente
                                                                     NTT
                                                         22 January 2024


            UDP-based Transport for Configured Subscriptions
                    draft-ietf-netconf-udp-notif-12

Abstract

   This document describes a UDP-based protocol for YANG notifications
   to collect data from network nodes.  A shim header is proposed to
   facilitate the data streaming directly from the publishing process on
   network processor of line cards to receivers.  The objective is to
   provide a lightweight approach to enable higher frequency and less
   performance impact on publisher and receiver processes compared to
   already established notification mechanisms.

Requirements Language

   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.

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."



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   This Internet-Draft will expire on 25 July 2024.

Copyright Notice

   Copyright (c) 2024 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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Configured Subscription to UDP-Notif  . . . . . . . . . . . .   4
   3.  UDP-Based Transport . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Design Overview . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Format of the UDP-Notif Message Header  . . . . . . . . .   5
     3.3.  Data Encoding . . . . . . . . . . . . . . . . . . . . . .   8
   4.  Options . . . . . . . . . . . . . . . . . . . . . . . . . . .   8
     4.1.  Segmentation Option . . . . . . . . . . . . . . . . . . .   9
     4.2.  Private Encoding Option . . . . . . . . . . . . . . . . .  10
   5.  Applicability . . . . . . . . . . . . . . . . . . . . . . . .  10
     5.1.  Congestion Control  . . . . . . . . . . . . . . . . . . .  11
     5.2.  Message Size  . . . . . . . . . . . . . . . . . . . . . .  12
     5.3.  Reliability . . . . . . . . . . . . . . . . . . . . . . .  12
   6.  Secured layer for UDP-notif . . . . . . . . . . . . . . . . .  12
     6.1.  Session lifecycle . . . . . . . . . . . . . . . . . . . .  13
       6.1.1.  DTLS Session Initiation . . . . . . . . . . . . . . .  13
       6.1.2.  Publish Data  . . . . . . . . . . . . . . . . . . . .  13
       6.1.3.  Session termination . . . . . . . . . . . . . . . . .  14
   7.  A YANG Data Model for Management of UDP-Notif . . . . . . . .  14
     7.1.  YANG to configure UDP-notif . . . . . . . . . . . . . . .  14
     7.2.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  16
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
     8.1.  IANA registries . . . . . . . . . . . . . . . . . . . . .  19
     8.2.  URI . . . . . . . . . . . . . . . . . . . . . . . . . . .  21
     8.3.  YANG module name  . . . . . . . . . . . . . . . . . . . .  21
   9.  Implementation Status . . . . . . . . . . . . . . . . . . . .  21
     9.1.  Open Source Publisher . . . . . . . . . . . . . . . . . .  21
     9.2.  Open Source Receiver Library  . . . . . . . . . . . . . .  22
     9.3.  Pmacct Data Collection  . . . . . . . . . . . . . . . . .  22
     9.4.  Huawei VRP  . . . . . . . . . . . . . . . . . . . . . . .  22



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   10. Security Considerations . . . . . . . . . . . . . . . . . . .  22
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  22
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  22
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  22
     12.2.  Informative References . . . . . . . . . . . . . . . . .  25
   Appendix A.  UDP-notif Examples . . . . . . . . . . . . . . . . .  26
     A.1.  Configuration for UDP-notif transport with DTLS
           disabled  . . . . . . . . . . . . . . . . . . . . . . . .  26
     A.2.  Configuration for UDP-notif transport with DTLS
           enabled . . . . . . . . . . . . . . . . . . . . . . . . .  27
     A.3.  YANG Push message with UDP-notif transport protocol . . .  30
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  31

1.  Introduction

   The mechanism to support a subscription of a continuous and
   customized stream of updates from a YANG datastore [RFC8342] is
   defined in [RFC8639] and [RFC8641] and is abbreviated as Sub-Notif.
   Requirements for Subscription to YANG Datastores are defined in
   [RFC7923].

   The mechanism separates the management and control of subscriptions
   from the transport used to deliver the data.  Three transport
   mechanisms, namely NETCONF transport [RFC8640], RESTCONF transport
   [RFC8650], and HTTPS transport [I-D.ietf-netconf-https-notif] have
   been defined so far for such notification messages.

   While powerful in their features and general in their architecture,
   the currently available transport mechanisms need to be complemented
   to support data publications at high velocity from network nodes that
   feature a distributed architecture.  The currently available
   transports are based on TCP and lack the efficiency needed to
   continuously send notifications at high velocity.

   This document specifies a transport option for Sub-Notif that
   leverages UDP.  Specifically, it facilitates the distributed data
   collection mechanism described in
   [I-D.ietf-netconf-distributed-notif].  In the case of publishing from
   multiple network processors on multiple line cards, centralized
   designs require data to be internally forwarded from those network
   processors to the push server, presumably on a route processor, which
   then combines the individual data items into a single consolidated
   stream.  The centralized data collection mechanism can result in a
   performance bottleneck, especially when large amounts of data are
   involved.






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   What is needed is a mechanism that allows for directly publishing
   from multiple network processors on line cards, without passing them
   through an additional processing stage for internal consolidation.
   The proposed UDP-based transport allows for such a distributed data
   publishing approach.

   *  Firstly, a UDP approach reduces the burden of maintaining a large
      amount of active TCP connections at the receiver, notably in cases
      where it collects data from network processors on line cards from
      a large amount of network nodes.

   *  Secondly, as no connection state needs to be maintained, UDP
      encapsulation can be easily implemented by the hardware of the
      publication streamer, which further improves performance.

   *  Ultimately, such advantages allow for a larger data analysis
      feature set, as more voluminous, finer grained data sets can be
      streamed to the receiver.

   The transport described in this document can be used for transmitting
   notification messages over both IPv4 and IPv6.

   This document describes the notification mechanism.  It is intended
   to be used in conjunction with [RFC8639], extended by
   [I-D.ietf-netconf-distributed-notif].

   Section 2 describes the control of the proposed transport mechanism.
   Section 3 details the notification mechanism and message format.
   Section 4 describes the use of options in the notification message
   header.  Section 5 covers the applicability of the proposed
   mechanism.  Section 6 describes a mechanism to secure the protocol in
   open networks.

2.  Configured Subscription to UDP-Notif

   This section describes how the proposed mechanism can be controlled
   using subscription channels based on NETCONF or RESTCONF.

   As specified in Sub-Notif, configured subscriptions contain the
   location information of all the receivers, including the IP address
   and the port number, so that the publisher can actively send UDP-
   Notif messages to the corresponding receivers.

   Note that receivers MAY NOT be already up and running when the
   configuration of the subscription takes effect on the monitored
   network node.  The first message MUST be a separate subscription-
   started notification to indicate the Receiver that the stream has
   started flowing.  Then, the notifications can be sent immediately



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   without delay.  All the subscription state notifications, as defined
   in Section 2.7 of [RFC8639], MUST be encapsulated in separate
   notification messages.

3.  UDP-Based Transport

   In this section, we specify the UDP-Notif Transport behavior.
   Section 3.1 describes the general design of the solution.
   Section 3.2 specifies the UDP-Notif message format and Section 3.3
   describes the encoding of the message payload.

3.1.  Design Overview

   As specified in Sub-Notif, the YANG data is encapsulated in a
   NETCONF/RESTCONF notification message, which is then encapsulated and
   carried using a transport protocols such as TLS or HTTP2.  This
   document defines a UDP based transport.  Figure 1 illustrates the
   structure of an UDP-Notif message.

   *  The Message Header contains information that facilitate the
      message transmission before deserializing the notification
      message.

   *  Notification Message is the encoded content that is transported by
      the publication stream.  The common encoding methods are listed in
      Section 3.2.  The structure of the Notification Message is defined
      in Section 2.6 of [RFC8639] and a YANG model has been proposed in
      [I-D.ahuang-netconf-notif-yang].
      [I-D.ietf-netconf-notification-messages] proposes a structure to
      send bundled notifications in a single message.

               +-------+  +--------------+  +--------------+
               |  UDP  |  |   Message    |  | Notification |
               |       |  |   Header     |  | Message      |
               +-------+  +--------------+  +--------------+

                    Figure 1: UDP-Notif Message Overview


3.2.  Format of the UDP-Notif Message Header

   The UDP-Notif Message Header contains information that facilitate the
   message transmission before deserializing the notification message.
   The data format is shown in Figure 2.







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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-----+-+-------+---------------+-------------------------------+
     | Ver |S|  MT   |  Header Len   |      Message Length           |
     +-----+-+-------+---------------+-------------------------------+
     |                     Message Publisher ID                      |
     +---------------------------------------------------------------+
     |                         Message ID                            |
     +---------------------------------------------------------------+
     ~                          Options                              ~
     +---------------------------------------------------------------+

                 Figure 2: UDP-Notif Message Header Format


   The Message Header contains the following field:

   *  Ver indicates the UDP-notif protocol header version.  The values
      are allocated by the IANA registry "UDP-notif header version".
      The current header version number is 1.

   *  S represents the space of media type specified in the MT field.
      When S is unset, MT represents the standard media types as defined
      in this document.  When S is set, MT represents a private space to
      be freely used for non standard encodings.  When S is set, the
      Private Encoding Option defined in Section 4.2 SHOULD be present
      in the UDP-notif message header.

   *  MT is a 4 bit identifier to indicate the media type used for the
      Notification Message. 16 types of encoding can be expressed.  When
      the S bit is unset, the following values apply:

      -  0: Reserved;

      -  1: application/yang-data+json [RFC8040]

      -  2: application/yang-data+xml [RFC8040]

      -  3: application/yang-data+cbor [RFC9254]

   *  Header Len is the length of the message header in octets,
      including both the fixed header and the options.









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   *  Message Length is the total length of the UDP-notif message within
      one UDP datagram, measured in octets, including the message
      header.  When the Notification Message is segmented using the
      Segmentation Options defined in Section 4.1 the Message Length is
      the total length of the current, segmented UDP-notif message, not
      the length of the entire Notification message.

   *  Message Publisher ID is a 32-bit identifier defined in
      [I-D.ietf-netconf-distributed-notif].  This identifier is unique
      to the publisher node and identifies the publishing process of the
      node to allow the disambiguation of an information source.
      Message unicity is obtained from the conjunction of the Message
      Publisher ID and the Message ID field described below.  If Message
      Publisher ID unicity is not preserved through the collection
      domain, the source IP address of the UDP datagram SHOULD be used
      in addition to the Message Publisher ID to identify the
      information source.  If a transport layer relay is used, Message
      Publisher ID unicity must be preserved through the collection
      domain.

   *  The Message ID is generated continuously by the publisher of UDP-
      Notif messages.  A publisher MUST use different Message ID values
      for different messages generated with the same Message Publisher
      ID.  Note that the main purpose of the Message ID is to
      reconstruct messages which are segmented using the segmentation
      option described in section Section 4.1.  The Message ID values
      SHOULD be incremented by one for each successive message
      originated with the same Message Publisher ID, so that message
      loss can be detected.  When the last value (2^32-1) of Message ID
      has been generated, the Message ID wraps around and restarts at 0.
      Different subscribers MAY share the same Message ID sequence.

   *  Options is a variable-length field in the TLV format.  When the
      Header Length is larger than 12 octets, which is the length of the
      fixed header, Options TLVs follow directly after the fixed message
      header (i.e., Message ID).  The details of the options are
      described in Section 4.

   All the binary fields MUST be encoded in network byte order (big
   endian).











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3.3.  Data Encoding

   UDP-Notif message data can be encoded in CBOR, XML or JSON format.
   It is conceivable that additional encodings may be supported in the
   future.  This can be accomplished by augmenting the subscription data
   model with additional identity statements used to refer to requested
   encodings.

   Private encodings can be using the S bit of the header.  When the S
   bit is set, the value of the MT field is left to be defined and
   agreed upon by the users of the private encoding.  An option is
   defined in Section 4.2 for more verbose encoding descriptions than
   what can be described with the MT field.

   Implementation MAY support multiple encoding methods per
   subscription.  When bundled notifications are supported between the
   publisher and the receiver, only subscribed notifications with the
   same encoding can be bundled in a given message.

4.  Options

   All the options are defined with the following format, illustrated in
   Figure 3.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +---------------+---------------+--------------------------------
     |     Type      |    Length     |    Variable-length data
     +---------------+---------------+--------------------------------

                      Figure 3: Generic Option Format

   *  Type: 1 octet describing the option type;

   *  Length: 1 octet representing the total number of octets in the
      TLV, including the Type and Length fields;

   *  Variable-length data: 0 or more octets of TLV Value.

   When more than one option is used in the UDP-notif header, options
   MUST be ordered by the Type value.  Messages with unordered options
   MAY be dropped by the Receiver.









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4.1.  Segmentation Option

   The UDP payload length is limited to 65527 bytes (65535 - 8 bytes).
   Application level headers will make the actual payload shorter.  Even
   though binary encodings such as CBOR may not require more space than
   what is left, more voluminous encodings such as JSON and XML may
   suffer from this size limitation.  Although IPv4 and IPv6 publishers
   can fragment outgoing packets exceeding their Maximum Transmission
   Unit (MTU), fragmented IP packets may not be desired for operational
   and performance reasons.

   Consequently, implementations of the mechanism SHOULD provide a
   configurable max-segment-size option to control the maximum size of a
   payload.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +---------------+---------------+-----------------------------+-+
     |     Type      |     Length    |        Segment Number       |L|
     +---------------+---------------+-----------------------------+-+

                    Figure 4: Segmentation Option Format

   The Segmentation Option is to be included when the message content is
   segmented into multiple segments.  Different segments of one message
   share the same Message ID.  An illustration is provided in Figure 4.
   The fields of this TLV are:

   *  Type: Generic option field which indicates a Segmentation Option.
      The Type value is to be assigned TBD1.

   *  Length: Generic option field which indicates the length of this
      option.  It is a fixed value of 4 octets for the Segmentation
      Option.

   *  Segment Number: 15-bit value indicating the sequence number of the
      current segment.  The first segment of a segmented message has a
      Segment Number value of 0.  The Segment Number cannot wrap around.

   *  L: is a flag to indicate whether the current segment is the last
      one of the message.  When 0 is set, the current segment is not the
      last one.  When 1 is set, the current segment is the last one,
      meaning that the total number of segments used to transport this
      message is the value of the current Segment Number + 1.

   An implementation of this specification SHOULD NOT rely on IP
   fragmentation by default to carry large messages.  An implementation
   of this specification SHOULD either restrict the size of individual



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   messages carried over this protocol, or support the segmentation
   option.  The implementor or user SHOULD take into account the IP
   layer header size when setting the max-segment-size parameter to
   avoid fragmentation at the IP layer.

   When a message has multiple options and is segmented using the
   described mechanism, all the options MUST be present on the first
   segment ordered by the options Type.  The rest of segmented messages
   MAY include all the options ordered by options type.

   The receiver SHOULD support the reception of unordered segments.  The
   implementation of the receiver SHOULD provide an option to discard
   the received segments if, after some time, one of the segments is
   still missing and the reassembly of the message is not possible.

4.2.  Private Encoding Option

   The space to describe private encodings in the MT field of the UDP-
   Notif header being limited, an option is provided to describe custom
   encodings.  The fields of this option are as follows.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +---------------+---------------+--------------------------------
     |     Type      |     Length    |   Variable length enc. descr.
     +---------------+---------------+--------------------------------


                  Figure 5: Private Encoding Option Format

   *  Type: Generic option field which indicates a Private Encoding
      Option.  The Type value is to be assigned TBD2.

   *  Length: Generic option field which indicates the length of this
      option.  It is a variable value.

   *  Enc. Descr: The description of the private encoding used for this
      message.  The values to be used for such private encodings is left
      to be defined by the users of private encodings.

   This option SHOULD only be used when the S bit of the header is set,
   as providing a private encoding description for standard encodings is
   meaningless.

5.  Applicability

   In this section, we provide an applicability statement for the
   proposed mechanism, following the recommendations of [RFC8085].



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   The proposed mechanism falls in the category of UDP applications
   "designed for use within the network of a single network operator or
   on networks of an adjacent set of cooperating network operators, to
   be deployed in controlled environments", as defined in [RFC8085].
   Implementations of the proposed mechanism SHOULD thus follow the
   recommendations in place for such specific applications.  In the
   following, we discuss recommendations on congestion control, message
   size guidelines, reliability considerations and security
   considerations.

   The main use case of the proposed mechanism is the collection of
   statistical metrics for accounting purposes, where potential loss is
   not a concern, but should however be reported (such as IPFIX Flow
   Records exported with UDP [RFC7011]).  Such metrics are typically
   exported in a periodical subscription as described in Section 3.1 of
   [RFC8641].

5.1.  Congestion Control

   The proposed application falls into the category of applications
   performing transfer of large amounts of data.  It is expected that
   the operator using the solution configures QoS on its related flows.
   As per [RFC8085], such applications MAY choose not to implement any
   form of congestion control, but follow the following principles.

   It is NOT RECOMMENDED to use the proposed mechanism over congestion-
   sensitive network paths.  The only environments where UDP-Notif is
   expected to be used are managed networks.  The deployments require
   that the network path has been explicitly provisioned to handle the
   traffic through traffic engineering mechanisms, such as rate limiting
   or capacity reservations.

   Implementation of the proposal SHOULD NOT push unlimited amounts of
   traffic by default, and SHOULD require the users to explicitly
   configure such a mode of operation.

   Burst mitigation through packet pacing is RECOMMENDED.  Disabling
   burst mitigation SHOULD require the users to explicitly configure
   such a mode of operation.

   Applications SHOULD monitor packet losses and provide means to the
   user for retrieving information on such losses.  The UDP-Notif
   Message ID can be used to deduce congestion based on packet loss
   detection.  Hence the receiver can notify the Publisher to use a
   lower streaming rate.  The interaction to control the streaming rate
   on the Publisher is out of the scope of this document.





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5.2.  Message Size

   [RFC8085] recommends not to rely on IP fragmentation for messages
   whose size result in IP packets exceeding the MTU along the path.
   The segmentation option of the current specification permits
   segmentation of the UDP Notif message content without relying on IP
   fragmentation.  Implementation of the current specification SHOULD
   allow for the configuration of the MTU.

   It is RECOMMENDED that the size of a Notification Message is small
   and segmentation does not result in segmenting the message into too
   much segments to avoid dropping the entire message when there is a
   lost segment.  When a Notification Message is large, it is
   RECOMMENDED to use a reliable transport such as HTTPS-notif
   [I-D.ietf-netconf-https-notif].

5.3.  Reliability

   A receiver implementation for this protocol SHOULD deal with
   potential loss of packets carrying a part of segmented payload, by
   discarding packets that were received, but cannot be re-assembled as
   a complete message within a given amount of time.  This time SHOULD
   be configurable.

6.  Secured layer for UDP-notif

   In unsecured networks, UDP-notif messages MUST be secured or
   encrypted.  In this section, a mechanism using DTLS 1.3 to secure
   UDP-notif protocol is presented.  The following sections defines the
   requirements for the implementation of the secured layer of DTLS for
   UDP-notif.  No DTLS 1.3 extensions are defined in this document.

   The DTLS 1.3 protocol [RFC9147] is designed to meet the requirements
   of applications that need to secure datagram transport.
   Implementations using DTLS to secure UDP-notif messages MUST use DTLS
   1.3 protocol as defined in [RFC9147].

   When this security layer is used, the Publisher MUST always be a DTLS
   client, and the Receiver MUST always be a DTLS server.  The Receivers
   MUST support accepting UDP-notif Messages on the specified UDP port,
   but MAY be configurable to listen on a different port.  The Publisher
   MUST support sending UDP-notif messages to the specified UDP port,
   but MAY be configurable to send messages to a different port.  The
   Publisher MAY use any source UDP port for transmitting messages.







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6.1.  Session lifecycle

6.1.1.  DTLS Session Initiation

   The Publisher initiates a DTLS connection by sending a DTLS
   ClientHello to the Receiver.  Implementations MAY support the denial
   of service countermeasures defined by DTLS 1.3 if a given deployment
   can ensure that DoS attacks are not a concern.  When these
   countermeasures are used, the Receiver responds with a DTLS
   HelloRetryRequest containing a stateless cookie.  The Publisher sends
   a second DTLS ClientHello message containing the received cookie.
   Details can be found in Section 5.1 of [RFC9147].

   When DTLS is implemented, the Publisher MUST NOT send any UDP-notif
   messages before the DTLS handshake has successfully completed.  Early
   data mechanism (also known as 0-RTT data) as defined in [RFC9147]
   MUST NOT be used.

   Implementations of this security layer MUST support DTLS 1.3
   [RFC9147] and MUST support the mandatory to implement cipher suite
   TLS_AES_128_GCM_SHA256 and SHOULD implement TLS_AES_256_GCM_SHA384
   and TLS_CHACHA20_POLY1305_SHA256 cipher suites, as specified in TLS
   1.3 [RFC8446].  If additional cipher suites are supported, then
   implementations MUST NOT negotiate a cipher suite that employs NULL
   integrity or authentication algorithms.

   Where confidentiality protection with DTLS is required,
   implementations must negotiate a cipher suite that employs a non-NULL
   encryption algorithm.

6.1.2.  Publish Data

   When DTLS is used, all UDP-notif messages MUST be published as DTLS
   "application_data".  It is possible that multiple UDP-notif messages
   are contained in one DTLS record, or that a publication message is
   transferred in multiple DTLS records.  The application data is
   defined with the following ABNF [RFC5234] expression:

   APPLICATION-DATA = 1*UDP-NOTIF-FRAME

   UDP-NOTIF-FRAME = MSG-LEN SP UDP-NOTIF-MSG

   MSG-LEN = NONZERO-DIGIT *DIGIT

   SP = %d32

   NONZERO-DIGIT = %d49-57




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   DIGIT = %d48 / NONZERO-DIGIT

   UDP-NOTIF-MSG is defined in Section 3.

   The Publisher SHOULD attempt to avoid IP fragmentation by using the
   Segmentation Option in the UDP-notif message.

6.1.3.  Session termination

   A Publisher MUST close the associated DTLS connection if the
   connection is not expected to deliver any UDP-notif Messages later.
   It MUST send a DTLS close_notify alert before closing the connection.
   A Publisher (DTLS client) MAY choose to not wait for the Receiver's
   close_notify alert and simply close the DTLS connection.  Once the
   Receiver gets a close_notify from the Publisher, it MUST reply with a
   close_notify.

   When no data is received from a DTLS connection for a long time, the
   Receiver MAY close the connection.  Implementations SHOULD set the
   timeout value to 10 minutes but application specific profiles MAY
   recommend shorter or longer values.  The Receiver (DTLS server) MUST
   attempt to initiate an exchange of close_notify alerts with the
   Publisher before closing the connection.  Receivers that are
   unprepared to receive any more data MAY close the connection after
   sending the close_notify alert.

   Although closure alerts are a component of TLS and so of DTLS, they,
   like all alerts, are not retransmitted by DTLS and so may be lost
   over an unreliable network.

7.  A YANG Data Model for Management of UDP-Notif

7.1.  YANG to configure UDP-notif

   The YANG model described in Section 7.2 defines a new receiver
   instance for UDP-notif transport.  When this transport is used, four
   new leaves and a dtls container allow configuring UDP-notif receiver
   parameters.













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  module: ietf-udp-notif-transport

    augment /sn:subscriptions/snr:receiver-instances
              /snr:receiver-instance/snr:transport-type:
      +--:(udp-notif)
         +--rw udp-notif-receiver
            +--rw remote-address         inet:ip-address-no-zone
            +--rw remote-port            inet:port-number
            +--rw dtls! {dtls13}?
            |  +--rw client-identity!
            |  |  +--rw (auth-type)
            |  |     +--:(certificate) {client-ident-x509-cert}?
            |  |     |     ...
            |  |     +--:(raw-public-key) {client-ident-raw-public-key}?
            |  |     |     ...
            |  |     +--:(tls13-epsk) {client-ident-tls13-epsk}?
            |  |           ...
            |  +--rw server-authentication
            |  |  +--rw ca-certs! {server-auth-x509-cert}?
            |  |  |  +--rw (local-or-truststore)
            |  |  |        ...
            |  |  +--rw ee-certs! {server-auth-x509-cert}?
            |  |  |  +--rw (local-or-truststore)
            |  |  |        ...
            |  |  +--rw raw-public-keys! {server-auth-raw-public-key}?
            |  |  |  +--rw (local-or-truststore)
            |  |  |        ...
            |  |  +--rw tls13-epsks?       empty
            |  |          {server-auth-tls13-epsk}?
            |  +--rw hello-params {tlscmn:hello-params}?
            |  |  +--rw tls-versions
            |  |  |  +--rw tls-version*   identityref
            |  |  +--rw cipher-suites
            |  |     +--rw cipher-suite*   identityref
            |  +--rw keepalives {tls-client-keepalives}?
            |     +--rw peer-allowed-to-send?   empty
            |     +--rw test-peer-aliveness!
            |        +--rw max-wait?       uint16
            |        +--rw max-attempts?   uint8
            +--rw enable-segmentation?   boolean {segmentation}?
            +--rw max-segment-size?      uint32 {segmentation}?










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7.2.  YANG Module

   This YANG module is used to configure, on a publisher, a receiver
   willing to consume notification messages.  This module augments the
   "ietf-subscribed-notif-receivers" module to define a UDP-notif
   transport receiver.  The grouping "udp-notif-receiver-grouping"
   defines the necessary parameters to configure the transport defined
   in this document using the generic "udp-client-grouping" grouping
   from the "ietf-udp-client" module
   [I-D.ahuang-netconf-udp-client-server] and the "tls-client-grouping"
   defined in the "ietf-tls-client" module
   [I-D.ietf-netconf-tls-client-server].

   <CODE BEGINS> file "ietf-udp-notif-transport@2024-01-22.yang"
   module ietf-udp-notif-transport {
     yang-version 1.1;
     namespace
       "urn:ietf:params:xml:ns:yang:ietf-udp-notif-transport";
     prefix unt;
     import ietf-subscribed-notifications {
       prefix sn;
       reference
         "RFC 8639: Subscription to YANG Notifications";
     }
     import ietf-subscribed-notif-receivers {
       prefix snr;
       reference
         "RFC YYYY: An HTTPS-based Transport for
                    Configured Subscriptions";
     }
     import ietf-udp-client {
       prefix udpc;
       reference
         "RFC ZZZZ: YANG Grouping for UDP Clients and UDP Servers";
     }
     import ietf-tls-client {
       prefix tlsc;
       reference
         "RFC TTTT: YANG Groupings for TLS Clients and TLS Servers";
     }

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

        Authors:  Guangying Zheng
                  <mailto:zhengguangying@huawei.com>



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                  Tianran Zhou
                  <mailto:zhoutianran@huawei.com>
                  Thomas Graf
                  <mailto:thomas.graf@swisscom.com>
                  Pierre Francois
                  <mailto:pierre.francois@insa-lyon.fr>
                  Alex Huang Feng
                  <mailto:alex.huang-feng@insa-lyon.fr>
                  Paolo Lucente
                  <mailto:paolo@ntt.net>";

     description
       "Defines UDP-Notif as a supported transport for subscribed
       event notifications.

       Copyright (c) 2023 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 Revised 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-to-be; see the RFC
       itself for full legal notices.";

     revision 2024-01-22 {
       description
         "Initial revision";
       reference
         "RFC-to-be: UDP-based Transport for Configured Subscriptions";
     }

    /*
     * FEATURES
     */
     feature encode-cbor {
       description
         "This feature indicates that CBOR encoding of notification
          messages is supported.";
     }
     feature dtls13 {
       description
         "This feature indicates that DTLS 1.3 encryption of UDP
          packets is supported.";
     }
     feature segmentation {



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       description
         "This feature indicates segmentation of notification messages
         is supported.";
     }

    /*
     * IDENTITIES
     */
     identity udp-notif {
       base sn:transport;
       description
         "UDP-Notif is used as transport for notification messages
           and state change notifications.";
     }

     identity encode-cbor {
       base sn:encoding;
       description
         "Encode data using CBOR as described in RFC 9254.";
       reference
         "RFC 9254: CBOR Encoding of Data Modeled with YANG";
     }

     grouping udp-notif-receiver-grouping {
       description
         "Provides a reusable description of a UDP-Notif target
         receiver.";

       uses udpc:udp-client-grouping;

       container dtls {
         if-feature dtls13;
         presence dtls;
         uses tlsc:tls-client-grouping {
           // Using tls-client-grouping without TLS1.2 parameters
           // allowing only DTLS 1.3
           refine "client-identity/auth-type/tls12-psk" {
             // create the logical impossibility of enabling TLS1.2
             if-feature "not tlsc:client-ident-tls12-psk";
           }
           refine "server-authentication/tls12-psks" {
             // create the logical impossibility of enabling TLS1.2
             if-feature "not tlsc:server-auth-tls12-psk";
           }
         }
         description
           "Container for configuring DTLS 1.3 parameters.";
       }



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       leaf enable-segmentation {
         if-feature segmentation;
         type boolean;
         default false;
         description
           "The switch for the segmentation feature. When disabled, the
           publisher will not allow fragment for a very large data";
       }

       leaf max-segment-size {
         when "../enable-segmentation = 'true'";
         if-feature segmentation;
         type uint32;
         description
           "UDP-Notif provides a configurable max-segment-size to
           control the size of each segment (UDP-Notif header, with
           options, included).";
       }
     }

     augment "/sn:subscriptions/snr:receiver-instances/" +
             "snr:receiver-instance/snr:transport-type" {
       case udp-notif {
         container udp-notif-receiver {
           description
             "The UDP-notif receiver to send notifications to.";
           uses udp-notif-receiver-grouping;
         }
       }
       description
         "Augment the transport-type choice to include the 'udp-notif'
          transport.";
     }
   }
   <CODE ENDS>

8.  IANA Considerations

   This document describes several new registries, the URIs from IETF
   XML Registry and the registration of a two new YANG module names.

8.1.  IANA registries

   This document is creating 3 registries called "UDP-notif media
   types", "UDP-notif option types", and "UDP-notif header version"
   under the new group "UDP-notif protocol".  The registration procedure
   is made using the Standards Action process defined in [RFC8126].




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   The first requested registry is the following:

     Registry Name: UDP-notif media types
     Registry Category: UDP-notif protocol.
     Registration Procedure: Standard Action as defined in RFC8126
     Maximum value: 15

   These are the initial registrations for "UDP-notif media types":

     Value: 0
     Description: Reserved
     Reference: RFC-to-be

     Value: 1
     Description: media type application/yang-data+json
     Reference: <xref target="RFC8040"/>

     Value: 2
     Description: media type application/yang-data+xml
     Reference: <xref target="RFC8040"/>

     Value: 3
     Description: media type application/yang-data+cbor
     Reference: <xref target="RFC9254"/>

   The second requested registry is the following:

     Registry Name: UDP-notif option types
     Registry Category: UDP-notif protocol.
     Registration Procedure: Standard Action as defined in RFC8126
     Maximum value: 255

   These are the initial registrations for "UDP-notif options types":

     Value: 0
     Description: Reserved
     Reference: RFC-to-be

     Value: TBD1 (suggested value: 1)
     Description: Segmentation Option
     Reference: RFC-to-be

     Value: TBD2 (suggested value: 2)
     Description: Private Encoding Option
     Reference: RFC-to-be

   The third requested registry is the following:




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     Registry Name: UDP-notif header version
     Registry Category: UDP-notif protocol.
     Registration Procedure: Standard Action as defined in RFC8126
     Maximum value: 7

   These are the initial registrations for "UDP-notif header version":

     Value: 0
     Description: UDP based Publication Channel for Streaming Telemetry
     Reference: draft-ietf-netconf-udp-pub-channel-05

     Value: 1
     Description: UDP-based Transport for Configured Subscriptions.
     Reference: RFC-to-be

8.2.  URI

   IANA is also requested to assign a two new URI from the IETF XML
   Registry [RFC3688].  The following two URIs are suggested:

   URI: urn:ietf:params:xml:ns:yang:ietf-udp-notif-transport
   Registrant Contact: The IESG.
   XML: N/A; the requested URI is an XML namespace.

8.3.  YANG module name

   This document also requests a two new YANG module names in the YANG
   Module Names registry [RFC8342] with the following suggestions:

   name: ietf-udp-notif
   namespace: urn:ietf:params:xml:ns:yang:ietf-udp-notif-transport
   prefix: unt
   reference: RFC-to-be

9.  Implementation Status

   Note to the RFC-Editor: Please remove this section before publishing.

9.1.  Open Source Publisher

   INSA Lyon implemented this document for a YANG Push publisher in an
   example implementation.

   The open source code can be obtained here: [INSA-Lyon-Publisher].







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9.2.  Open Source Receiver Library

   INSA Lyon implemented this document for a YANG Push receiver as a
   library.

   The open source code can be obtained here: [INSA-Lyon-Receiver].

9.3.  Pmacct Data Collection

   The open source YANG push receiver library has been integrated into
   the Pmacct open source Network Telemetry data collection.

9.4.  Huawei VRP

   Huawei implemented this document for a YANG Push publisher in their
   VRP platform.

10.  Security Considerations

   [RFC8085] states that "UDP applications that need to protect their
   communications against eavesdropping, tampering, or message forgery
   SHOULD employ end-to-end security services provided by other IETF
   protocols".  As mentioned above, the proposed mechanism is designed
   to be used in controlled environments, as defined in [RFC8085] also
   known as "limited domains", as defined in [RFC8799].  Thus, a
   security layer is not necessary required.  Nevertheless, a DTLS layer
   MUST be implemented in unsecured networks.  A specification of udp-
   notif using DTLS is presented in Section 6.

11.  Acknowledgements

   The authors of this documents would like to thank Alexander Clemm,
   Benoit Claise, Eric Voit, Huiyang Yang, Kent Watsen, Mahesh
   Jethanandani, Marco Tollini, Hannes Tschofenig, Michael Tuxen, Rob
   Wilton, Sean Turner, Stephane Frenot, Timothy Carey, Tim Jenkins, Tom
   Petch and Yunan Gu for their constructive suggestions for improving
   this document.

12.  References

12.1.  Normative References










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   [I-D.ahuang-netconf-udp-client-server]
              Feng, A. H., Francois, P., and K. Watsen, "YANG Grouping
              for UDP Clients and UDP Servers", Work in Progress,
              Internet-Draft, draft-ahuang-netconf-udp-client-server-01,
              22 January 2024,
              <https://datatracker.ietf.org/api/v1/doc/document/draft-
              ahuang-netconf-udp-client-server/>.

   [I-D.ietf-netconf-distributed-notif]
              Zhou, T., Zheng, G., Voit, E., Graf, T., and P. Francois,
              "Subscription to Distributed Notifications", Work in
              Progress, Internet-Draft, draft-ietf-netconf-distributed-
              notif-08, 6 October 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-
              distributed-notif-08>.

   [I-D.ietf-netconf-https-notif]
              Jethanandani, M. and K. Watsen, "An HTTPS-based Transport
              for YANG Notifications", Work in Progress, Internet-Draft,
              draft-ietf-netconf-https-notif-14, 18 January 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-
              https-notif-14>.

   [I-D.ietf-netconf-tls-client-server]
              Watsen, K., "YANG Groupings for TLS Clients and TLS
              Servers", Work in Progress, Internet-Draft, draft-ietf-
              netconf-tls-client-server-34, 28 December 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-
              tls-client-server-34>.

   [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>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <https://www.rfc-editor.org/info/rfc5234>.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,
              <https://www.rfc-editor.org/info/rfc6991>.




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   [RFC8085]  Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
              Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
              March 2017, <https://www.rfc-editor.org/info/rfc8085>.

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

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

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

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [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>.

   [RFC8640]  Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard,
              E., and A. Tripathy, "Dynamic Subscription to YANG Events
              and Datastores over NETCONF", RFC 8640,
              DOI 10.17487/RFC8640, September 2019,
              <https://www.rfc-editor.org/info/rfc8640>.

   [RFC8650]  Voit, E., Rahman, R., Nilsen-Nygaard, E., Clemm, A., and
              A. Bierman, "Dynamic Subscription to YANG Events and
              Datastores over RESTCONF", RFC 8650, DOI 10.17487/RFC8650,
              November 2019, <https://www.rfc-editor.org/info/rfc8650>.

   [RFC9147]  Rescorla, E., Tschofenig, H., and N. Modadugu, "The
              Datagram Transport Layer Security (DTLS) Protocol Version
              1.3", RFC 9147, DOI 10.17487/RFC9147, April 2022,
              <https://www.rfc-editor.org/info/rfc9147>.

   [RFC9254]  Veillette, M., Ed., Petrov, I., Ed., Pelov, A., Bormann,
              C., and M. Richardson, "Encoding of Data Modeled with YANG
              in the Concise Binary Object Representation (CBOR)",
              RFC 9254, DOI 10.17487/RFC9254, July 2022,
              <https://www.rfc-editor.org/info/rfc9254>.



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12.2.  Informative References

   [I-D.ahuang-netconf-notif-yang]
              Feng, A. H., Francois, P., Graf, T., and B. Claise, "YANG
              model for NETCONF Event Notifications", Work in Progress,
              Internet-Draft, draft-ahuang-netconf-notif-yang-03, 20
              October 2023, <https://datatracker.ietf.org/doc/html/
              draft-ahuang-netconf-notif-yang-03>.

   [I-D.ietf-netconf-notification-messages]
              Voit, E., Jenkins, T., Birkholz, H., Bierman, A., and A.
              Clemm, "Notification Message Headers and Bundles", Work in
              Progress, Internet-Draft, draft-ietf-netconf-notification-
              messages-08, 17 November 2019,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-
              notification-messages-08>.

   [INSA-Lyon-Publisher]
              "INSA Lyon, YANG Push publisher example implementation",
              <https://github.com/network-analytics/udp-notif-scapy>.

   [INSA-Lyon-Receiver]
              "INSA Lyon, YANG Push receiver library implementation",
              <https://github.com/network-analytics/udp-notif-
              c-collector>.

   [Paolo-Lucente-Pmacct]
              "Paolo Lucente, Pmacct open source Network Telemetry Data
              Collection", <https://github.com/pmacct/pmacct>.

   [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>.

   [RFC7011]  Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
              "Specification of the IP Flow Information Export (IPFIX)
              Protocol for the Exchange of Flow Information", STD 77,
              RFC 7011, DOI 10.17487/RFC7011, September 2013,
              <https://www.rfc-editor.org/info/rfc7011>.

   [RFC7923]  Voit, E., Clemm, A., and A. Gonzalez Prieto, "Requirements
              for Subscription to YANG Datastores", RFC 7923,
              DOI 10.17487/RFC7923, June 2016,
              <https://www.rfc-editor.org/info/rfc7923>.






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   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              RFC 7951, DOI 10.17487/RFC7951, August 2016,
              <https://www.rfc-editor.org/info/rfc7951>.

   [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>.

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

   [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>.

   [RFC8799]  Carpenter, B. and B. Liu, "Limited Domains and Internet
              Protocols", RFC 8799, DOI 10.17487/RFC8799, July 2020,
              <https://www.rfc-editor.org/info/rfc8799>.

Appendix A.  UDP-notif Examples

   This non-normative section shows two examples of how the the "ietf-
   udp-notif-transport" YANG module can be used to configure a [RFC8639]
   based publisher to send notifications to a receiver and an example of
   a YANG Push notification message using UDP-notif transport protocol.

A.1.  Configuration for UDP-notif transport with DTLS disabled

   This example shows how UDP-notif can be configured without DTLS
   encryption.




















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   =============== NOTE: '\' line wrapping per RFC 8792 ================

   <?xml version='1.0' encoding='UTF-8'?>
   <config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <subscriptions xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-\
   notifications">
       <subscription>
         <id>6666</id>
         <stream-subtree-filter>some-subtree-filter</stream-subtree-fil\
   ter>
         <stream>some-stream</stream>
         <transport xmlns:unt="urn:ietf:params:xml:ns:yang:ietf-udp-not\
   if-transport">unt:udp-notif</transport>
         <encoding>encode-json</encoding>
         <receivers>
           <receiver>
             <name>subscription-specific-receiver-def</name>
             <receiver-instance-ref xmlns="urn:ietf:params:xml:ns:yang:\
   ietf-subscribed-notif-receivers">global-udp-notif-receiver-def</rece\
   iver-instance-ref>
           </receiver>
         </receivers>
         <periodic xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push">
           <period>6000</period>
         </periodic>
       </subscription>
       <receiver-instances xmlns="urn:ietf:params:xml:ns:yang:ietf-subs\
   cribed-notif-receivers">
         <receiver-instance>
           <name>global-udp-notif-receiver-def</name>
           <udp-notif-receiver xmlns="urn:ietf:params:xml:ns:yang:ietf-\
   udp-notif-transport">
             <remote-address>192.0.5.1</remote-address>
             <remote-port>12345</remote-port>
             <enable-segmentation>false</enable-segmentation>
             <max-segment-size/>
           </udp-notif-receiver>
         </receiver-instance>
       </receiver-instances>
     </subscriptions>
   </config>

A.2.  Configuration for UDP-notif transport with DTLS enabled

   This example shows how UDP-notif can be configured with DTLS
   encryption.





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   =============== NOTE: '\' line wrapping per RFC 8792 ================

   <?xml version='1.0' encoding='UTF-8'?>
   <config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <subscriptions xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-\
   notifications">
       <subscription>
         <id>6666</id>
         <stream-subtree-filter>some-subtree-filter</stream-subtree-fil\
   ter>
         <stream>some-stream</stream>
         <transport xmlns:unt="urn:ietf:params:xml:ns:yang:ietf-udp-not\
   if-transport">unt:udp-notif</transport>
         <encoding>encode-json</encoding>
         <receivers>
           <receiver>
             <name>subscription-specific-receiver-def</name>
             <receiver-instance-ref xmlns="urn:ietf:params:xml:ns:yang:\
   ietf-subscribed-notif-receivers">global-udp-notif-receiver-dtls-def<\
   /receiver-instance-ref>
           </receiver>
         </receivers>
         <periodic xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push">
           <period>6000</period>
         </periodic>
       </subscription>
       <receiver-instances xmlns="urn:ietf:params:xml:ns:yang:ietf-subs\
   cribed-notif-receivers">
         <receiver-instance>
           <name>global-udp-notif-receiver-dtls-def</name>
           <udp-notif-receiver xmlns="urn:ietf:params:xml:ns:yang:ietf-\
   udp-notif-transport">
             <remote-address>192.0.5.1</remote-address>
             <remote-port>12345</remote-port>
             <enable-segmentation>false</enable-segmentation>
             <max-segment-size/>
             <dtls>
               <client-identity>
                 <tls13-epsk>
                   <local-definition>
                     <key-format>ct:octet-string-key-format</key-format>
                     <cleartext-key>BASE64VALUE=</cleartext-key>
                   </local-definition>
                   <external-identity>example_external_id</external-ide\
   ntity>
                   <hash>sha-256</hash>
                   <context>example_context_string</context>
                   <target-protocol>8443</target-protocol>



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                   <target-kdf>12345</target-kdf>
                 </tls13-epsk>
               </client-identity>
               <server-authentication>
                 <ca-certs>
                   <local-definition>
                     <certificate>
                       <name>Server Cert Issuer #1</name>
                       <cert-data>BASE64VALUE=</cert-data>
                     </certificate>
                     <certificate>
                       <name>Server Cert Issuer #2</name>
                       <cert-data>BASE64VALUE=</cert-data>
                     </certificate>
                   </local-definition>
                 </ca-certs>
                 <ee-certs>
                   <local-definition>
                     <certificate>
                       <name>My Application #1</name>
                       <cert-data>BASE64VALUE=</cert-data>
                     </certificate>
                     <certificate>
                       <name>My Application #2</name>
                       <cert-data>BASE64VALUE=</cert-data>
                     </certificate>
                   </local-definition>
                 </ee-certs>
                 <raw-public-keys>
                   <local-definition>
                     <public-key>
                       <name>corp-fw1</name>
                       <public-key-format>ct:subject-public-key-info-fo\
   rmat</public-key-format>
                       <public-key>BASE64VALUE=</public-key>
                     </public-key>
                     <public-key>
                       <name>corp-fw2</name>
                       <public-key-format>ct:subject-public-key-info-fo\
   rmat</public-key-format>
                       <public-key>BASE64VALUE=</public-key>
                     </public-key>
                   </local-definition>
                 </raw-public-keys>
                 <tls13-epsks/>
               </server-authentication>
               <keepalives>
                 <test-peer-aliveness>



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                   <max-wait>30</max-wait>
                   <max-attempts>3</max-attempts>
                 </test-peer-aliveness>
               </keepalives>
             </dtls>
           </udp-notif-receiver>
         </receiver-instance>
       </receiver-instances>
     </subscriptions>
   </config>

A.3.  YANG Push message with UDP-notif transport protocol

   This example shows how UDP-notif is used as a transport protocol to
   send a "push-update" notification [RFC8641] encoded in JSON
   [RFC7951].

   Assuming the publisher needs to send the JSON payload showed in
   Figure 6, the UDP-notif transport is encoded following the Figure 7.
   The UDP-notif message is then encapsulated in a UDP frame.

              {
                  "ietf-notification:notification": {
                      "eventTime": "2023-02-10T08:00:11.22Z",
                      "ietf-yang-push:push-update": {
                          "id": 1011,
                          "datastore-contents": {
                              "ietf-interfaces:interfaces": [
                                  {
                                      "interface": {
                                          "name": "eth0",
                                          "oper-status": "up"
                                      }
                                  }
                              ]
                          }
                      }
                  }
              }

                     Figure 6: JSON Payload to be sent










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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-----+-+-------+---------------+-------------------------------+
     |Ver=1|0|  MT=1 | Header_Len=12 |      Message_Length=230       |
     +-----+-+-------+---------------+-------------------------------+
     |                   Message Publisher ID=2                      |
     +---------------------------------------------------------------+
     |                      Message ID=1563                          |
     +---------------------------------------------------------------+
     |              YANG Push JSON payload (Len=218 octets)          |
     |{"ietf-notification:notification":{"eventTime":"2023-02-10T08:0|
     |0:11.22Z","ietf-yang-push:push-update":{"id":1011,"datastore-co|
     |ntents":{"ietf-interfaces:interfaces":[{"interface":{"name":"et|
     |h0","oper-status":"up"}}]}}}}                                  |
     +---------------------------------------------------------------+

                   Figure 7: UDP-notif transport message

Authors' Addresses

   Guangying Zheng
   Huawei
   101 Yu-Hua-Tai Software Road
   Nanjing
   Jiangsu,
   China
   Email: zhengguangying@huawei.com


   Tianran Zhou
   Huawei
   156 Beiqing Rd., Haidian District
   Beijing
   China
   Email: zhoutianran@huawei.com


   Thomas Graf
   Swisscom
   Binzring 17
   CH- Zuerich 8045
   Switzerland
   Email: thomas.graf@swisscom.com








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   Pierre Francois
   INSA-Lyon
   Lyon
   France
   Email: pierre.francois@insa-lyon.fr


   Alex Huang Feng
   INSA-Lyon
   Lyon
   France
   Email: alex.huang-feng@insa-lyon.fr


   Paolo Lucente
   NTT
   Siriusdreef 70-72
   Hoofddorp, WT 2132
   Netherlands
   Email: paolo@ntt.net































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