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Versions: 00 01 draft-ietf-netconf-udp-pub-channel

NETCONF                                                         G. Zheng
Internet-Draft                                                   T. Zhou
Intended status: Standards Track                                A. Clemm
Expires: January 3, 2018                                          Huawei
                                                            July 2, 2017


         UDP based Publication Channel for Streaming Telemetry
                 draft-zheng-netconf-udp-pub-channel-00

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 http://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 January 3, 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
   (http://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 . . . . . . . . . . . .   6
     4.1.  Data Format . . . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  Options . . . . . . . . . . . . . . . . . . . . . . . . .   8
       4.2.1.  Reliability Option  . . . . . . . . . . . . . . . . .   8
       4.2.2.  Authentication Option . . . . . . . . . . . . . . . .   9
       4.2.3.  Encryption Option . . . . . . . . . . . . . . . . . .   9
     4.3.  Data encoding . . . . . . . . . . . . . . . . . . . . . .   9
   5.  YANG Data Model for Subscription Management . . . . . . . . .   9
   6.  Retransmission Request  . . . . . . . . . . . . . . . . . . .  10
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     10.2.  Informative References . . . . . . . . . . . . . . . . .  11
   Appendix A.  An Appendix  . . . . . . . . . . . . . . . . . . . .  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



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   the management and control of subscriptions from the transport that
   is used to actually stream and deliver the data.  Two transports have
   been defined so far, Netconf and Restconf/HTTP2.

   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.  Specifically, there are two aspects that
   need to be addressed:

   1.  The transports that have been defined so far, Netconf and HTTP2,
       are ultimately based on TCP and lack the efficiency needed to
       stream data continuously at high velocity.  A lighterweight, more
       efficient transport, e.g. a transport based on UDP is needed.

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

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

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

   2.  The current design involves a single push server.  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.  This
       centralized data collection mechanism can result in a performance
       bottleneck, especially when large amounts of data are involved.
       What is needed instead is 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.

   This document specifies a distributed data collection mechanism which
   can directly push data from line cards to a collector by using a UDP
   based publication channel.  Specifically, the following are
   specified:

   o  A higher-performance transport option for YANG-Push that leverages
      UDP.




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   o  Extensions to YANG-Push's subscription model that allow a single
      subscription to control multiple internal data originators that
      each generate their own independent telemetry streams.  Note:
      Because the ability to support multiple streams via a single
      subscription might be applicable to other transports as well, this
      aspect might be split into a separate specification in future
      revisions of this draft.

   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.

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.

   Component subscription: A subscription that defines the data from
   each individual entity which is managed and controlled by a single
   subscription server.

   Subscription agent: An agent that streams telemetry data per the
   terms of a component subscription.

3.  Solution Overview

   The typical distributed data collection solution is shown in figure
   1.  The subscription server located in the main board receives the
   subscription requests or configurations.  It may be colocated, not
   necessary, with a Netconf server which interacts with outside
   clients.  When receiving a subscription request, the subscription
   server decomposes the subscription into multiple component
   subscriptions, each involving data from a separate internal telemetry
   source, for example a line card.  The component subscriptions are
   distributed within the device to the subscription agents located in
   line cards.  Subsequently, each line card generates its own stream of
   telemetry data, collecting and encapsulating the packets per the
   component subscription and streaming it to the designated data
   collector.

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




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   retransmission request to the subscriber server for further
   processing.

   Subscription server and subscription agents interact with each other
   in several ways:

   o  Subscription agents need to have a registration or announcement
      handshake with the subscription server, so the subscription server
      is aware of them and of lifecycle events (such as subscription
      agents appearing and disappearing).

   o  The subscription server relays the component subscriptions to the
      subscription agents.

   o  The subscription agents indicate status of component subscriptions
      to the subscription server.  The status of the overall "master"
      subscription is maintained by the subscription server.  The
      subscription server is also responsible for notifying the
      subscriber in case of any problems of component subscriptions.

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






























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                retransmission +    +
                request        |    | subscription
                        +------------------------+
                        |      |    |  Main Board|
                        |   +--v----v--------+   |
                        |   |  subscription  |   |
                        |   |  server        |   |
                        |   +--+----+-----+--+   |
                        |      |    |     |      |   internal
                        +------------------------+   subscription
                               |    |     |          distribution
               +---------------+    |     +--------------+
               |                    |                    |
     +------------------+  +------------------+  +------------------+
     |         |        |  |        |         |  |       |          |
     | +-------v------+ |  | +------v-------+ |  | +-----v--------+ |
     | | subscription | |  | | subscription | |  | | subscription | |
     | | agent        | |  | | agent        | |  | | agent        | |
     | +--------------+ |  | +--------------+ |  | +--------------+ |
     |    Line Card 1   |  |    Line Card 2   |  |    Line Card n   |
     +---------+--------+  +--------+---------+  +----------+-------+
               |                    |                       |
               |                    | Publication Channel   |
               +--------------+     |     +-----------------+
                              |     |     |
                            +-v-----v-----v-+
                            |               |
                            |   Collector   |
                            |               |
                            +---------------+



4.  UDP Transport for Publication Channel

   In [I-D.voit-netconf-notification-messages], the transport
   independent message header is proposed for the notification use.  The
   following shim header refers to and implements that message header
   definition.

4.1.  Data Format

   The data format of the UDP based based publication transport 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
     +---------------------------------------------------------------+
     |                     UDP Header                                ~
     +-------+---------------+-----------------------+---------------+
     | Vers. |    Flag       |   Reserved            |  Msg-Gen-ID   |
     +-------+---------------+-----------------------+---------------+
     |                      Device ID                                |
     +---------------------------------------------------------------+
     |                      Timestamp (Seconds)                      |
     +---------------------------------------------------------------+
     |                      Timestamp (MicroSeconds)                 |
     +---------------------------------------------------------------+
     |                      Options                                  ~
     +---------------------------------------------------------------+
     |                      Message Content                          ~
     +---------------------------------------------------------------+


   Right after the UDP header, a simple inform header is attached to
   carry the necessary information with regard to the streaming mode.

   o  The Vers. field represents the PDU encoding version.  The initial
      version value is 0.

   o  The Flag is a bitmap indicating what features this packet has and
      the corresponding options attached.  Each bit associates to one
      feature and one option.  When the bit is set to 1, the associated
      feature is enabled and the option is attached.  The sequence of
      the presence of the options also follows the position in the
      bitmap.  Right now 3 options are specified.

      *  bit 0, the reliability option;

      *  bit 1, the authentication option;

      *  bit 2, the encryption option;

      *  other bits are reserved.

   o  The Msg-Gen-ID stands for the message generator ID.  It identifies
      the process, either on main board or line cards, which created the
      packet.

   o  The Device ID identifies the device with an global unique number
      that will not repeat among all the managed devices.  It can be
      generated by some unique device information like MAC address.




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   o  The Timestamp, including the second part and the microsecond part,
      indicate the time the message was packaged and sent to the
      receiver.  The Timestamp is defined per RFC 3339.

   o  The details of the Options will be described in the respective
      sections.

   After the inform header is the real content which is encoded.  The
   actual encoding is based on the subscription, e.g., in binary with
   GPB or CBOR [RFC7049].

   More details of the content encoding is TBD.

4.2.  Options

4.2.1.  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 is set to 1.  The following option 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                           |
     +---------------------------------------------------------------+

   The notification ID is generated continuously by the message
   generator.  Different subsrcibers 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], Subscriber B subscribes
      [1,2,4,5,7,8,9].

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

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

4.2.2.  Authentication Option

   TBD

4.2.3.  Encryption Option

   TBD

4.3.  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.

5.  YANG Data Model for Subscription Management

   To enable the UDP based publication transport, the subscription
   configuration need to provide necessary information.  The
   subscription management YANG Model extends ietf-subscribed-
   notifications described [I-D.ietf-netconf-yang-push]








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   +--rw subscription-config {configured-subscriptions}?
   | + ...
   | +--rw receivers
   | | + ...
   | | +--rw protocol? transport-protocol
   | | | +--rw udp-transport-type? udp-transport-type
   | | |   +--rw reliable?
   | | |   +--rw authentication?
   | | |   +--rw encryption?

   As in the above YANG tree, when the transport protocol is set to UDP,
   retries indicates the maximum retry times of the reliable streaming
   mode, and the timeout indicates the time out for retry in reliable
   streaming mode.

   TBD.  Note this YANG tree just to show we need to extend subcription
   mode, including the configurations and the RPCs.  More details will
   be added later.

6.  Retransmission Request

   TBD

7.  IANA Considerations

   TBD

8.  Security Considerations

9.  Acknowledgements

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

10.  References

10.1.  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,
              <http://www.rfc-editor.org/info/rfc2119>.

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





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   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <http://www.rfc-editor.org/info/rfc7950>.

10.2.  Informative References

   [I-D.ietf-netconf-subscribed-notifications]
              Voit, E., Clemm, A., Prieto, A., Nilsen-Nygaard, E., and
              A. Tripathy, "Custom Subscription to Event Notifications",
              draft-ietf-netconf-subscribed-notifications-02 (work in
              progress), April 2017.

   [I-D.ietf-netconf-yang-push]
              Clemm, A., Voit, E., Prieto, A., Tripathy, A., Nilsen-
              Nygaard, E., Bierman, A., and B. Lengyel, "Subscribing to
              YANG datastore push updates", draft-ietf-netconf-yang-
              push-07 (work in progress), June 2017.

   [I-D.voit-netconf-notification-messages]
              Voit, E., Bierman, A., Clemm, A., and T. Jenkins,
              "Notification Message Headers and Bundles", draft-voit-
              netconf-notification-messages-00 (work in progress), April
              2017.

Appendix A.  An Appendix

Authors' Addresses

   Guangying Zheng
   Huawei
   Nanjing, Jiangsu
   China

   Fax:   +
   Email: zhengguangying@huawei.com


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

   Email: zhoutianran@huawei.com







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   Alexander Clemm
   Huawei
   2330 Central Expressway
   Santa Clara, California
   USA

   Email: alexander.clemm@huawei.com












































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