NETCONF                                                         G. Zheng
Internet-Draft                                                   T. Zhou
Intended status: Standards Track                                  Huawei
Expires: September 28, 2020                                     A. Clemm
                                                               Futurewei
                                                                 T. Graf
                                                                Swisscom
                                                             P. Francois
                                                               INSA-Lyon
                                                              P. Lucente
                                                                     NTT
                                                          March 27, 2020


         UDP based Publication Channel for Streaming Telemetry
                 draft-unyte-netconf-udp-pub-channel-01

Abstract

   This document describes a UDP-based publication channel for streaming
   telemetry use to collect data from devices.  A new shim header is
   proposed to facilitate the distributed data collection mechanism
   which directly pushes data from line cards to the collector.  Because
   of the lightweight UDP encapsulation, higher frequency and better
   transit performance can be achieved.

Requirements Language

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

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 28, 2020.



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Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminologies . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Transport Mechanisms  . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Dynamic Subscription  . . . . . . . . . . . . . . . . . .   4
     3.2.  Configured Subscription . . . . . . . . . . . . . . . . .   5
   4.  UDP Transport for Publication Channel . . . . . . . . . . . .   6
     4.1.  Design Overview . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  Data Format of the UPC Message Header . . . . . . . . . .   7
     4.3.  Options . . . . . . . . . . . . . . . . . . . . . . . . .   8
       4.3.1.  Fragmentation Option  . . . . . . . . . . . . . . . .   9
     4.4.  Data Encoding . . . . . . . . . . . . . . . . . . . . . .  10
   5.  Using DTLS to Secure UPC  . . . . . . . . . . . . . . . . . .  10
     5.1.  Transport . . . . . . . . . . . . . . . . . . . . . . . .  10
     5.2.  Port Assignment . . . . . . . . . . . . . . . . . . . . .  11
     5.3.  DTLS Session Initiation . . . . . . . . . . . . . . . . .  11
     5.4.  Sending Data  . . . . . . . . . . . . . . . . . . . . . .  12
     5.5.  Closure . . . . . . . . . . . . . . . . . . . . . . . . .  12
   6.  Congestion Control  . . . . . . . . . . . . . . . . . . . . .  13
   7.  A YANG Data Model for Management of UPC . . . . . . . . . . .  13
   8.  YANG Module . . . . . . . . . . . . . . . . . . . . . . . . .  13
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  17
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  17
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  17
     12.2.  Informative References . . . . . . . . . . . . . . . . .  19
     12.3.  URIs . . . . . . . . . . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19






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1.  Introduction

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

   Sub-Notif [RFC8639] defines a mechanism that allows a collector to
   subscribe to updates of YANG-defined data that is maintained in a
   YANG [RFC7950] datastore.  The mechanism separates the management and
   control of subscriptions from the transport that is used to actually
   stream and deliver the data.  Three transports, NETCONF transport
   [RFC8640], RESTCONF transport [I-D.ietf-netconf-restconf-notif] and
   HTTPS transport [I-D.ietf-netconf-https-notif], have been defined so
   far for the notification messages.

   While powerful in its features and general in its architecture, in
   its current form the mechanism needs to be extended to stream
   telemetry data at high velocity from devices that feature a
   distributed architecture.  The transports that have been defined so
   far, NETCONF and HTTP, are ultimately based on TCP and lack the
   efficiency needed to stream data continuously at high velocity.  A
   lighter-weight, more efficient transport, e.g. a transport based on
   UDP is needed.

   o  Firstly, data collector will suffer a lot of TCP connections from,
      for example, many line cards equipped on different devices.

   o  Secondly, as no connection state needs to be maintained, UDP
      encapsulation can be easily implemented by hardware which will
      further improve the performance.

   o  Thirdly, because of the lightweight UDP encapsulation, higher
      frequency and better transit performance can be achieved, which is
      important for streaming telemetry.

   This document specifies a higher-performance transport option for
   Sub-Notif that leverages UDP.  Specifically, it facilitates the
   distributed data collection mechanism described in
   [I-D.zhou-netconf-multi-stream-originators].  In the case of data
   originating from multiple line cards, the centralized design requires
   data to be internally forwarded from those line cards to the push
   server, presumably on a main board, which then combines the
   individual data items into a single consolidated stream.  The



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   centralized data collection mechanism can result in a performance
   bottleneck, especially when large amounts of data are involved.  What
   is needed instead is the support for a distributed mechanism that
   allows to directly push multiple individual substreams, e.g. one from
   each line card, without needing to first pass them through an
   additional processing stage for internal consolidation, but still
   allowing those substreams to be managed and controlled via a single
   subscription.  The proposed UDP based Publication Channel (UPC)
   natively supports the distributed data collection mechanism.

   The transport described in this document can be used for transmitting
   notification messages over both IPv4 and IPv6 [RFC8200].

   While this document will focus on the data publication channel, the
   subscription can be used in conjunction with the mechanism proposed
   in [RFC8639] with extensions
   [I-D.zhou-netconf-multi-stream-originators].

2.  Terminologies

   Streaming Telemetry: refers to sending a continuous stream of
   operational data from a device to a remote receiver.  This provides
   an ability to monitor a network from remote and to provide network
   analytics.

3.  Transport Mechanisms

   For a complete pub-sub mechanism, this section will describe how the
   UPC is used to interact with the Subscription Channel relying on
   NETCONF or RESTCONF.

3.1.  Dynamic Subscription

   Dynamic subscriptions for Sub-Notif are configured and managed via
   signaling messages transported over NETCONF [RFC6241] or RESTCONF
   [RFC8040].  The Sub-Notif defined RPCs which are sent and responded
   via the Subscription Channel (a), between the Subscriber and the
   Subscription Server of the Publisher.  In this case, only one
   Receiver is associated with the Subscriber.  In the Publisher, there
   may be multiple data originators.  Notification messages are pushed
   on separate channels (b), from different data originators to the
   Receiver.









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   +--------------+                         +--------------+
   |  Collector   |                         |  Publisher   |
   |              |                         |              |
   |  (a)   (b)   |                         |  (a)    (b)  |
   +--+------+----+                         +--+-------+---+
      |      |                                 |       |
      |      |     RPC:establish-subscription  |       |
      +---------------------------------------->       |
      |      |     RPC Reply: OK               |       |
      <----------------------------------------+       |
      |      |     UPC:notifications           |       |
      |      <-----------------------------------------+
      |      |                                 |       |
      |      |     RPC:modify-subscription     |       |
      +---------------------------------------->       |
      |      |     RPC Reply: OK               |       |
      <----------------------------------------+       |
      |      |     UPC:notifications           |       |
      |      <-----------------------------------------+
      |      |                                 |       |
      |      |     RPC:delete-subscription     |       |
      +---------------------------------------->       |
      |      |     RPC Reply: OK               |       |
      <----------------------------------------+       |
      |      |                                 |       |
      |      |                                 |       |
      +      +                                 +       +

                 Fig. 2 Call Flow For Dynamic Subscription

   In the case of dynamic subscription, the Receiver and the Subscriber
   SHOULD be colocated.  So UPC can use the source IP address of the
   Subscription Channel as it's destination IP address.  The Receiver
   MUST support listening messages at the IANA-assigned PORT-X or PORT-
   Y, but MAY be configured to listen at a different port.

   For dynamic subscription, the Publication Channels MUST share fate
   with the subscription session.  In other words, when the delete-
   subscription is received or the subscription session is broken, all
   the associated Publication Channels MUST be closed.

3.2.  Configured Subscription

   For a Configured Subscription, there is no guarantee that the
   Subscriber is currently in place with the associated Receiver(s).  As
   defined in Sub-Notif, the subscription configuration contains the
   location information of all the receivers, including the IP address




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   and the port number.  So that the data originator can actively send
   generated messages to the corresponding Receivers via the UPC.

   The first message MUST be a separate subscription-started
   notification to indicate the Receiver that the pushing is started.
   Then, the notifications can be sent immediately without any wait.

   All the subscription state notifications, as defined in [RFC8639],
   MUST be encapsulated to be separated notification messages.

   +--------------+                         +--------------+
   |  Collector   |                         |  Publisher   |
   |              |                         |              |
   |  (a)   (b)   |                         |  (a)    (b)  |
   +--+------+----+                         +--+-------+---+
      |      |                                 |       |
      |      |     Capability Exchange         |       |
      <---------------------------------------->       |
      |      |                                 |       |
      |      |     Edit config(create)         |       |
      +---------------------------------------->       |
      |      |     RPC Reply: OK               |       |
      <----------------------------------------+       |
      |      |     UPC:subscription started    |       |
      |      <-----------------------------------------+
      |      |     UPC:notifications           |       |
      |      <-----------------------------------------+
      |      |                                 |       |
      |      |     Edit config(delete)         |       |
      +---------------------------------------->       |
      |      |     RPC Reply: OK               |       |
      <----------------------------------------+       |
      |      |     UPC:subscription terminated |       |
      |      <-----------------------------------------+
      |      |                                 |       |
      |      |                                 |       |
      +      +                                 +       +

               Fig. 3 Call Flow For Configured Subscription

4.  UDP Transport for Publication Channel

4.1.  Design Overview

   As specified in Sub-Notif, the telemetry data is encapsulated in the
   NETCONF/RESTCONF notification message, which is then encapsulated and
   carried in the transport protocols, e.g.  TLS, HTTP2.  The following
   figure shows the overview of the typical UPC message structure.



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   o  The Message Header contains information that can facilitate the
      message transmission before de-serializing the notification
      message.

   o  Notification Message is the encoded content that the publication
      channel transports.  The common encoding method includes GPB [1],
      CBOR [RFC7049], JSON, and XML.
      [I-D.ietf-netconf-notification-messages] describes the structure
      of the Notification Message for both single notification and
      multiple bundled notifications.

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

                  Fig. 4 UDP Publication Message Overview

4.2.  Data Format of the UPC Message Header

   The UPC Message Header contains information that can facilitate the
   message transmission before de-serializing the notification message.
   The data format is shown 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
     +-------+---------------+-------+-------------------------------+
     | Vers. | Header Length |  ET   |       Message Length          |
     +-------+---------------+-------+-------------------------------+
     |                       Message-Generator-ID                    |
     +---------------------------------------------------------------+
     |                       Message ID                              |
     +---------------------------------------------------------------+
     ~                       Options                                 ~
     +---------------------------------------------------------------+


                     Fig. 3 UPC Message Header Format

   The Message Header contains the following field:

   o  Vers.: represents the PDU (Protocol Data Unit) encoding version.
      The initial version value is 0.

   o  Header Length: is the length of the message header, measured in
      octets, including both the fixed header and the options.





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   o  ET: is a 4 bits identifier to indicate the encoding type used for
      the Notification Message. 16 types of encoding can be expressed:

      *  0: GPB;

      *  1: CBOR;

      *  2: JSON;

      *  3: XML;

      *  others are reserved.

   o  Message Length: is the total length of the message within one UDP
      datagram, measured in octets, including the message header.

   o  Message-Generator-ID: is a 32-bit identifier of the process which
      created the notification message.  This allows disambiguation of
      an information source, such as the identification of different
      line cards sending the notification messages.  The source IP
      address of the UDP datagrams SHOULD NOT be interpreted as the
      identifier for the host that originated the UPC message.  The
      entity sending the UPC message could be merely a relay.

   o  The Message ID is generated continuously by the message generator.
      Different subscribers share the same Message ID sequence.

   o  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 follows directly after the fixed
      message header(i.e., Message ID).  The details of the Options are
      described in the respective sections below.

4.3.  Options

   All the options are defined with the following format:

      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    |
     +---------------+---------------+-------------------------------+
     ~                            Value                              ~
     +---------------------------------------------------------------+

                    Fig. 5 Fragmentation Option Format

   o  Type: 1 octet of the value Type;



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   o  Length: 1 octet of the TLV Length, including the Type and Length;

   o  Value: 0 or more octets of TLV Value.

4.3.1.  Fragmentation Option

   UDP palyload has a theoretical length limitation to 65535.  Other
   encapsulation headers will make the actual payload even shorter.
   Binary encodings like GPB and CBOR can make the message compact.  So
   that the message can be encapsulated within one UDP packet, and
   fragmentation will not easily happen.  However, text encodings like
   JSON and XML can easily make the message exceed the UDP length
   limitation.

   On the other hand, IPv4 and IPv6 will fragment when the IP packet
   exceeds the Maximum Transmission Unit(MTU).  Fragmented IP packets
   have risk to be dropped by the intermediate network devices.

   UPC provides a configurable max-fragmentation-size to control the
   size of each message.

      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    |
     +---------------+---------------+-----------------------------+-+
     |            Fragment Number                                  |L|
     +-------------------------------------------------------------+-+

                    Fig. 6 Fragmentation Option Format

   The Fragmentation Option is available when the message content is
   fragmented into multiple pieces.  Different fragments of one message
   share the same Message ID.  This option contains:

   Type: indicates Fragmentation Option.  The Type value is to be
   asigned.

   Length: is a fixed value of 6 octets.

   Fragment Number: indicates the sequence number of the current
   fragment.

   L: is a flag to indicate whether the current fragment is the last
   one.  When 0 is set, current fragment is not the last one, hence more
   fragments are expected.  When 1 is set, current fragment is the last
   one.




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4.4.  Data Encoding

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

   Implementation may support different encoding method per
   subscription.  When bundled notifications is supported between the
   publisher and the receiver, only subscribed notifications with the
   same encoding can be bundled as one message.

5.  Using DTLS to Secure UPC

   The Datagram Transport Layer Security (DTLS) protocol [RFC6347] is
   designed to meet the requirements of applications that need secure
   datagram transport.

   DTLS can be used as a secure transport to counter all the primary
   threats to UDP based Publication Channel:

   o  Confidentiality to counter disclosure of the message contents.

   o  Integrity checking to counter modifications to a message on a hop-
      by-hop basis.

   o  Server or mutual authentication to counter masquerade.

   In addition, DTLS also provides:

   o  A cookie exchange mechanism during handshake to counter Denial of
      Service attacks.

   o  A sequence number in the header to counter replay attacks.

5.1.  Transport

   As shown in Figure 7, the DTLS is layered next to the UDP transport
   is to provide reusable security and authentication functions over
   UDP.  No DTLS extension is required to enable UPC messages over DTLS.










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                      +-----------------------------+
                      |           UPC Message       |
                      +-----------------------------+
                      |            DTLS             |
                      +-----------------------------+
                      |            UDP              |
                      +-----------------------------+
                      |            IP               |
                      +-----------------------------+

                Fig. 7: Protocol Stack for DTLS secured UPC

   The application implementer will map a unique combination of the
   remote address, remote port number, local address, and local port
   number to a session.

   Each UPC message is delivered by the DTLS record protocol, which
   assigns a sequence number to each DTLS record.  Although the DTLS
   implementer may adopt a queue mechanism to resolve reordering, it may
   not assure that all the messages are delivered in order when mapping
   on the UDP transport.

   Since UDP is an unreliable transport, with DTLS, an originator or
   relay may not realize that a collector has gone down or lost its DTLS
   connection state, so messages may be lost.

   The DTLS record has its own sequence number, the encryption and
   decryption will done by DTLS layer, UPC Message layer will not
   concern this.

5.2.  Port Assignment

   The Publisher is always a DTLS client, and the Receiver is always a
   DTLS server.  The Receivers MUST support accepting UPC Messages on
   the UDP port PORT-Y, but MAY be configurable to listen on a different
   port.  The Publisher MUST support sending UPC messages to the UDP
   port PORT-Y, but MAY be configurable to send messages to a different
   port.  The Publisher MAY use any source UDP port for transmitting
   messages.

5.3.  DTLS Session Initiation

   The Publisher initiates a DTLS connection by sending a DTLS Client
   Hello to the Receiver.  Implementations MUST support the denial of
   service countermeasures defined by DTLS.  When these countermeasures
   are used, the Receiver responds with a DTLS Hello Verify Request
   containing a cookie.  The Publisher responds with a DTLS Client Hello
   containing the received cookie, which initiates the DTLS handshake.



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   The Publisher MUST NOT send any UPC messages before the DTLS
   handshake has successfully completed.

   Implementations MUST support DTLS 1.0 [RFC4347] and MUST support the
   mandatory to implement cipher suite, which is
   TLS_RSA_WITH_AES_128_CBC_SHA [RFC5246] as specified in DTLS 1.0.  If
   additional cipher suites are supported, then implementations MUST NOT
   negotiate a cipher suite that employs NULL integrity or
   authentication algorithms.

   Where privacy is REQUIRED, then implementations must either negotiate
   a cipher suite that employs a non-NULL encryption algorithm or else
   achieve privacy by other means, such as a physically secured network.

5.4.  Sending Data

   All UPC messages MUST be sent as DTLS "application_data".  It is
   possible that multiple UPC messages be contained in one DTLS record,
   or that a publication message be transferred in multiple DTLS
   records.  The application data is defined with the following ABNF
   [RFC5234] expression:

   APPLICATION-DATA = 1*UPC-FRAME

   UPC-FRAME = MSG-LEN SP UPC-MSG

   MSG-LEN = NONZERO-DIGIT *DIGIT

   SP = %d32

   NONZERO-DIGIT = %d49-57

   DIGIT = %d48 / NONZERO-DIGIT

   UPC-MSG is defined in section 5.2.

5.5.  Closure

   A Publisher MUST close the associated DTLS connection if the
   connection is not expected to deliver any UPC 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
   (where the application decides what "long" means), Receiver MAY close



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   the connection.  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.

6.  Congestion Control

   Congestion control mechanisms that respond to congestion by reducing
   traffic rates and establish a degree of fairness between flows that
   share the same path are vital to the stable operation of the Internet
   [RFC2914].  While efficient, UDP has no build-in congestion control
   mechanism.  Because streaming telemetry can generate unlimited
   amounts of data, transferring this data over UDP is generally
   problematic.  It is not recommended to use the UDP based publication
   channel over congestion-sensitive network paths.  The only
   environments where the UDP based publication channel may be used are
   managed networks.  The deployments require the network path has been
   explicitly provisioned for the UDP based publication channel through
   traffic engineering mechanisms, such as rate limiting or capacity
   reservations.  The UPC message contains continuous Message ID which
   can be used to deduce the congestion based on the packet loss
   detected by the collector.  Hence the collector can notice the device
   to use a lower exporting rate.  The interaction to control the
   exporting rate on the device is out of the scope of this document.

7.  A YANG Data Model for Management of UPC

   The YANG model defined in Section 9 has two leafs augmented into one
   place of Sub-Notif [RFC8639], plus one identities.

    module: ietf-upc-subscribed-notifications
     augment /sn:subscriptions/sn:subscription/sn:receivers/sn:receiver:
       +--rw address?   inet:ip-address
       +--rw port?      inet:port-number
       +--rw enable-fragmentation?  boolean
       +--rw max-fragmentation-size?  uint32

8.  YANG Module

<CODE BEGINS> file "ietf-upc-subscribed-notifications@2020-03-26.yang"
module ietf-upc-subscribed-notifications {
  yang-version 1.1;
  namespace
    "urn:ietf:params:xml:ns:yang:ietf-upc-subscribed-notifications";



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  prefix upcsn;
  import ietf-subscribed-notifications {
    prefix sn;
    reference
      "RFC 8639: Subscription to YANG Notifications";
  }
  import ietf-inet-types {
    prefix inet;
    reference
      "RFC 6991: Common YANG Data Types";
  }

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

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

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

     Editor:   Alexander Clemm
               <mailto:alexander.clemm@huawei.com>";


  description
    "Defines UDP Publish Channel as a supported transport for subscribed
    event notifications.

    Copyright (c) 2018 IETF Trust and the persons identified as authors
    of the code.  All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, is permitted pursuant to, and subject to the license
    terms contained in, the Simplified BSD License set forth in Section
    4.c of the IETF Trust's Legal Provisions Relating to IETF Documents
    (https://trustee.ietf.org/license-info).

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

    itself for full legal notices.";

  revision 2020-03-26 {
    description
      "Initial version";
    reference



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      "RFC XXXX: UDP based Publication Channel for Streaming Telemetry";
  }

  identity upc {
    base sn:transport;
    description
      "UPC 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 7049.";
    reference
      "RFC 7049: Concise Binary Object Representation";
  }

  identity encode-gpb {
    base sn:encoding;
    description
      "Encode data using GPB.";
  }

  grouping target-receiver {
    description
      "Provides a reusable description of a UPC target receiver.";
    leaf address {
      type inet:ip-address;
      description
        "IP address of target upc receiver, which can be IPv4 address or
         IPV6 address.";
    }
    leaf port {
      type inet:port-number;
      description
        "Port number of target UPC receiver, if not specify, system
         should use default port number.";
    }

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




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    leaf max-fragmentation-size {
      when "../enable-fragmentation = true";
      type uint32;
      description "UPC provides a configurable max-fragmentation-size
      to control the size of each message.";
    }
  }

  augment "/sn:subscriptions/sn:subscription/sn:receivers/sn:receiver" {
    description
      "This augmentation allows UPC specific parameters to be
       exposed for a subscription.";
    uses target-receiver;
  }
}
<CODE ENDS>

9.  IANA Considerations

   This RFC requests that IANA assigns three UDP port numbers in the
   "Registered Port Numbers" range with the service names "upc" and
   "upc-dtls".  These ports will be the default ports for the UDP based
   Publication Channel for NETCONF and RESTCONF.  Below is the
   registration template following the rules in [RFC6335].

   Service Name: upc

   Transport Protocol(s): UDP

   Assignee: IESG <iesg@ietf.org>

   Contact: IETF Chair <chair@ietf.org>

   Description: UDP based Publication Channel

   Reference: RFC XXXX

   Port Number: PORT-X

   Service Name: upc-dtls

   Transport Protocol(s): UDP

   Assignee: IESG <iesg@ietf.org>

   Contact: IETF Chair <chair@ietf.org>

   Description: UDP based Publication Channel (DTLS)



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   Reference: RFC XXXX

   Port Number: PORT-Y

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

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

   This document also requests a new YANG module name in the YANG Module
   Names registry [RFC7950] with the following suggestion:

name: ietf-upc-subscribed-notifications
namespace: urn:ietf:params:xml:ns:yang:ietf-upc-subscribed-notifications
prefix: upcsn
reference: RFC XXXX

10.  Security Considerations

   TBD

11.  Acknowledgements

   The authors of this documents would like to thank Eric Voit, Tim
   Jenkins, and Huiyang Yang for the initial comments.

12.  References

12.1.  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>.

   [RFC2914]  Floyd, S., "Congestion Control Principles", BCP 41,
              RFC 2914, DOI 10.17487/RFC2914, September 2000,
              <https://www.rfc-editor.org/info/rfc2914>.

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

   [RFC4347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security", RFC 4347, DOI 10.17487/RFC4347, April 2006,
              <https://www.rfc-editor.org/info/rfc4347>.



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   [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>.

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

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

   [RFC6335]  Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
              Cheshire, "Internet Assigned Numbers Authority (IANA)
              Procedures for the Management of the Service Name and
              Transport Protocol Port Number Registry", BCP 165,
              RFC 6335, DOI 10.17487/RFC6335, August 2011,
              <https://www.rfc-editor.org/info/rfc6335>.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
              January 2012, <https://www.rfc-editor.org/info/rfc6347>.

   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <https://www.rfc-editor.org/info/rfc7049>.

   [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>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

   [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>.




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   [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>.

12.2.  Informative References

   [I-D.ietf-netconf-https-notif]
              Jethanandani, M. and K. Watsen, "An HTTPS-based Transport
              for Configured Subscriptions", draft-ietf-netconf-https-
              notif-02 (work in progress), March 2020.

   [I-D.ietf-netconf-notification-messages]
              Voit, E., Jenkins, T., Birkholz, H., Bierman, A., and A.
              Clemm, "Notification Message Headers and Bundles", draft-
              ietf-netconf-notification-messages-08 (work in progress),
              November 2019.

   [I-D.ietf-netconf-restconf-notif]
              Voit, E., Rahman, R., Nilsen-Nygaard, E., Clemm, A., and
              A. Bierman, "Dynamic subscription to YANG Events and
              Datastores over RESTCONF", draft-ietf-netconf-restconf-
              notif-15 (work in progress), June 2019.

   [I-D.zhou-netconf-multi-stream-originators]
              Zhou, T., Zheng, G., Voit, E., and A. Clemm, "Subscription
              to Multiple Stream Originators", draft-zhou-netconf-multi-
              stream-originators-10 (work in progress), November 2019.

12.3.  URIs

   [1] https://developers.google.com/protocol-buffers/

Authors' Addresses

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

   Email: zhengguangying@huawei.com








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

   Email: zhoutianran@huawei.com


   Alexander Clemm
   Futurewei
   2330 Central Expressway
   Santa Clara, California
   USA

   Email: alex@futurewei.com


   Thomas Graf
   Swisscom
   Binzring 17
   Zuerich  8045
   Switzerland

   Email: thomas.graf@swisscom.com


   Pierre Francois
   INSA-Lyon
   Lyon
   France

   Email: pierre.francois@insa-lyon.fr


   Paolo Lucente
   NTT
   Siriusdreef 70-72
   Hoofddorp, WT  2132
   NL

   Email: paolo@ntt.net









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