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Versions: (draft-zheng-netconf-udp-pub-channel) 00 01

NETCONF                                                         G. Zheng
Internet-Draft                                                   T. Zhou
Intended status: Standards Track                                A. Clemm
Expires: May 15, 2018                                             Huawei
                                                       November 11, 2017


         UDP based Publication Channel for Streaming Telemetry
                 draft-ietf-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 May 15, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Solution Overview . . . . . . . . . . . . . . . . . . . . . .   4
   4.  UDP Transport for Publication Channel . . . . . . . . . . . .   5
     4.1.  Design Overview . . . . . . . . . . . . . . . . . . . . .   5
     4.2.  Data Format of the Message Header . . . . . . . . . . . .   6
     4.3.  Options . . . . . . . . . . . . . . . . . . . . . . . . .   8
       4.3.1.  Reliability Option  . . . . . . . . . . . . . . . . .   8
     4.4.  Data Encoding . . . . . . . . . . . . . . . . . . . . . .   9
   5.  Congestion Control  . . . . . . . . . . . . . . . . . . . . .   9
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  10
     9.3.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .  11
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

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 [I-D.ietf-netconf-subscribed-notifications] and YANG-Push
   [I-D.ietf-netconf-yang-push] 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



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   is used to actually stream and deliver the data.  Two transports have
   been defined so far, NETCONF [RFC6241] and RESTCONF [RFC8040].

   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 RESTCONF, are ultimately based on TCP (Transmission
   Control Protocol) 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 (User Datagram Protocol) 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
   YANG-Push 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 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 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 publication channel natively supports the
   distributed data collection mechanism.

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





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2.  Terminology

   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.  Solution Overview

   The typical distributed data collection solution is shown in Fig. 1.
   The Subscriber cannot see the Agents directly, so it will send the
   Global Subscription information to the Master (e.g., main board).
   When receiving a Global Subscription, the Subscription Server
   decomposes the subscription request into multiple Component
   Subscriptions, each involving data from a separate internal telemetry
   source, for example a line card.  The Component Subscriptions are
   distributed to the Component Subscription Server located in Agents.
   Subsequently, each Agent generates its own stream of telemetry data,
   collecting and encapsulating the packets per the Component
   Subscription and streaming them to the designated Collector.This
   distributed data collection mechanism may form multiple Publication
   Channels between the data originators and the Collector.  The
   Collector is able to assemble many pieces of data associated with one
   Global Subscription.

   The Publication Channel supports the reliable data streaming, for
   example for some alarm events.  The Collector has the option of
   deducing the packet loss and the disorder based on the information
   carried by the notification data.  And the Collector will decide the
   behavior to request retransmission.  The Collector can send the
   retransmission request to the subscriber server for further
   processing.

   The rest of the draft describes the UDP based publication channel.

















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                retransmission +    + Global
                request        |    | Subscription
                        +------------------------+
                        |      |    |  Master    |
                        |   +--v----v--------+   |
                        |   |  Subscription  |   |
                        |   |  Server        |   |
                        |   +--+----+-----+--+   |
                        |      |    |     |      |   internal
       Component        +------------------------+   subscription
       Subscription            |    |     |          distribution
               +---------------+    |     +--------------+
               |                    |                    |
     +------------------+  +------------------+  +------------------+
     |         |        |  |        |         |  |       |          |
     | +-------v------+ |  | +------v-------+ |  | +-----v--------+ |
     | | Component    | |  | | Component    | |  | | Component    | |
     | | Subscription | |  | | Subscription | |  | | Subscription | |
     | | Server       | |  | | Server       | |  | | Server       | |
     | +--------------+ |  | +--------------+ |  | +--------------+ |
     |       Agent 1    |  |      Agent 2     |  |        Agent n   |
     +---------+--------+  +--------+---------+  +----------+-------+
               |                    |                       |
               |                    | Publication Channel   |
               +--------------+     |     +-----------------+
                              |     |     |
                            +-v-----v-----v-+
                            |               |
                            |   Collector   |
                            |               |
                            +---------------+

                    Fig. 1 Distributed Data Collection

4.  UDP Transport for Publication Channel

4.1.  Design Overview

   As specified in YANG-Push, 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 UDP publication message structure.

   o  Next to the UDP encapsulation, the DTLS layer is to provide
      reusable security and authentication functions over UDP.






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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.

                                 +--------------+
                                 | Notification |
                                 | Message      |
                                 +--------------+

                                 +--------------+
                                 |   Message    |
                                 |   Header     |
                                 +--------------+

                                 +--------------+
                                 |     DTLS     |
                                 +--------------+

                                 +--------------+
                                 |      UDP     |
                                 +--------------+

                  Fig. 2 UDP Publication Message Overview

4.2.  Data Format of the Message Header

   The Message Header contains information that can facilitate the
   message transmission before de-serializing the notification message.
   The data format is shown as follows.















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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
     +-------+---------------+-------+-------------------------------+
     | Vers. |    Flag       |  ET   |      Length                   |
     +-------+---------------+-------+-------------------------------+
     |                      Notification-Time                        |
     +---------------------------------------------------------------+
     |                      Message-Generator-ID                     |
     +---------------------------------------------------------------+
     ~                      Options                                  ~
     +---------------------------------------------------------------+


                       Fig. 3 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  Flag: is a bitmap indicating what features this packet has and the
      corresponding options attached.  Each bit associates to one
      feature and one option data.  When the bit is set to 1, the
      associated feature is enabled and the option data is attached.
      The sequence of the presence of the options follows the bit order
      of the bitmap.  In this document, the flag is specified as
      follows:

      *  bit 0, the reliability flag;

      *  other bits are reserved.

   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  Length: is the total length of the message, measured in octets,
      including message header.




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   o  Message-Generator-ID: is a 32-bit identifier of the process which
      created the message notification.  This allows disambiguation of
      an information source, such as the identification of different
      line cards sending the notification messages.

   o  Notification-Time: is the time at which the message leaves the
      exporter, expressed in seconds since the UNIX epoch of 1 January
      1970 at 00:00 UTC, encoded as an unsigned 32-bit integer.

   o  Options: is a variable-length field.  The details of the Options
      will be described in the respective sections below.

4.3.  Options

   The order of packing the data fields in the Options field follows the
   bit order of the Flag field.

4.3.1.  Reliability Option

   The UDP based publication transport described in this document
   provides two streaming modes, the reliable mode an the unreliable
   mode, for different SLA (Service Level Agreement) and telemetry
   requirements.

   In the unreliable streaming mode, the line card pushes the
   encapsulated data to the data collector without any sequence
   information.  So the subscriber does not know whether the data is
   correctly received or not.  Hence no retransmission happens.

   The reliable streaming mode provides sequence information in the UDP
   packet, based on which the subscriber can deduce the packet loss and
   disorder.  Then the subscriber can decide whether to request the
   retransmission of the lost packets.

   In most case, the unreliable streaming mode is preferred.  Because
   the reliable streaming mode will cost more network bandwidth and
   precious device resource.  Different from the unreliable streaming
   mode, the line card cannot remove the sent reliable notifications
   immediately, but to keep them in the memory for a while.  Reliable
   notifications may be pushed multiple times, which will increase the
   traffic.  When choosing the reliable streaming mode or the unreliable
   streaming mode, the operate need to consider the reliable requirement
   together with the resource usage.

   When the reliability flag bit is set to 1 in the Flag field, the
   following option data will be attached





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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
     +---------------------------------------------------------------+
     |            Notification ID                                    |
     +---------------------------------------------------------------+
     |            Previous Notification ID                           |
     +---------------------------------------------------------------+

                     Fig. 4 Reliability Option Format

   The notification ID is generated continuously by the message
   generator.  Different subscribers share the same notification ID
   sequence.  Current ID and previous ID will be added in the packets.

   For example, there are two subscriber A and B,

   o  Notification IDs for the generator are : [1, 2, 3, 4, 5, 6, 7, 8,
      9], in which Subscriber A subscribes [1,2,3,6,7] and Subscriber B
      subscribes [1,2,4,5,7,8,9].

   o  Subscriber A will receive : [0,1][1,2][2,3][3,6][6,7].

   o  Subscriber B will receive : [0,1][1,2][2,4][4,5][5,7][7,8].

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.  Congestion Control

   While efficient, UDP has no build-in congestion control mechanism.
   It is not recommended to use the UDP based publication channel over
   congestion-sensitive network paths.  The deployments require the
   communications from exporters to collectors are always congestion
   controllable, i.e., the transport is over dedicated links or the
   streaming rate can be limited.






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6.  IANA Considerations

   TBD

7.  Security Considerations

   TBD

8.  Acknowledgements

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

9.  References

9.1.  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>.

   [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>.

   [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>.

9.2.  Informative References

   [I-D.ietf-netconf-notification-messages]
              Voit, E., Bierman, A., Clemm, A., and T. Jenkins,
              "Notification Message Headers and Bundles", draft-ietf-
              netconf-notification-messages-02 (work in progress),
              October 2017.





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   [I-D.ietf-netconf-subscribed-notifications]
              Voit, E., Clemm, A., Prieto, A., Nilsen-Nygaard, E., and
              A. Tripathy, "Custom Subscription to Event Streams",
              draft-ietf-netconf-subscribed-notifications-07 (work in
              progress), October 2017.

   [I-D.ietf-netconf-yang-push]
              Clemm, A., Voit, E., Prieto, A., Tripathy, A., Nilsen-
              Nygaard, E., Bierman, A., and B. Lengyel, "YANG Datastore
              Subscription", draft-ietf-netconf-yang-push-11 (work in
              progress), October 2017.

   [I-D.zhou-netconf-multi-stream-originators]
              Zhou, T., Zheng, G., Voit, E., Clemm, A., and A. Bierman,
              "Subscription to Multiple Stream Originators", draft-zhou-
              netconf-multi-stream-originators-00 (work in progress),
              October 2017.

9.3.  URIs

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

Appendix A.  Change Log

   (To be removed by RFC editor prior to publication)

   A.1. draft-ietf-zheng-udp-pub-channel-00 to v00

   o  Modified the telemetry header format.

   o  Add a section on the Authentication Option.

   o  Cleaned up the text and removed unnecessary TBDs.

   A.2. v01

   o  Removed the detailed description on distributed data collection
      mechanism from this document.  Mainly focused on the description
      of a UDP based publication channel for telemetry use.

   o  Modified the telemetry header format.

Authors' Addresses








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   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


   Alexander Clemm
   Huawei
   2330 Central Expressway
   Santa Clara, California
   USA

   Email: alexander.clemm@huawei.com


























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