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Network Working Group                                            T. Zhou
Internet-Draft                                                  G. Zheng
Intended status: Standards Track                                  Huawei
Expires: April 21, 2018                                          E. Voit
                                                           Cisco Systems
                                                                A. Clemm
                                                                  Huawei
                                                              A. Bierman
                                                               YumaWorks
                                                        October 18, 2017


              Subscription to Multiple Stream Originators
             draft-zhou-netconf-multi-stream-originators-00

Abstract

   This document describes the distributed data collection mechanism
   that allows multiple data streams to be managed using a single
   subscription.  Specifically, multiple data streams are pushed
   directly to the collector without passing through a broker for
   internal consolidation.

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 April 21, 2018.






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Copyright Notice

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

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Use Case 1: Data Collection from Devices with Main-board
           and Line-cards  . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Use Case 2: IoT Data Collection . . . . . . . . . . . . .   4
   3.  Solution Overview . . . . . . . . . . . . . . . . . . . . . .   5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .   8
   Appendix B.  Subscription Decomposition . . . . . . . . . . . . .   8
   Appendix C.  Publication Composition  . . . . . . . . . . . . . .   9
   Appendix D.  Examples . . . . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

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.

   YANG-Push [I-D.ietf-netconf-yang-push] defines a transport-
   independent subscription mechanism for datastore updates, in which a



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   subscriber can subscribe to a stream of datastore updates from a
   server, or update provider.  The current design involves subscription
   to a single push server.  This conceptually centralized model
   encounters efficiency limitations in cases where the data sources are
   themselves distributed, such as line cards in a piece of network
   equipment.  In such cases, it will be a lot more efficient to have
   each data source (e.g., each line card) originate its own stream of
   updates, rather than requiring updates to be tunneled through a
   central server where they are combined.  What is needed is a
   distributed mechanism that allows to directly push multiple
   individual data substreams, 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 will describe such distributed data collection
   mechanism and how it can work by extending existing YANG-Push
   mechanism.  The proposal is general enough to fit many scenarios.

2.  Use Cases

2.1.  Use Case 1: Data Collection from Devices with Main-board and Line-
      cards

   For data collection from devices with main-board and line-cards,
   existing YANG-Push solutions consider only one push server typically
   reside in the main board.  As shown in the following figure, data are
   collected from line cards and aggregate to the main board as one
   consolidated stream.  So the main board can easily become the
   performance bottle-neck.  The optimization is to apply the
   distributed data collection mechanism which can directly push data
   from line cards to a collector.  On one hand, this will reduce the
   cost of scarce compute and memory resources on the main board for
   data processing and assembling.  On the other hand, distributed data
   push can off-load the streaming traffic to multiple interfaces.
















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                  +-------------------------------------+
                  |              collector              |
                  +------^-----------^-----------^------+
                         |           |           |
                         |           |           |
                  +-------------------------------------+
                  |      |           |           |      |
                  |      |     +-----+------+    |      |
                  |      |     | main board |    |      |
                  |      |     +--^-----^---+    |      |
                  |      |        |     |        |      |
                  |      |    +---+     +---+    |      |
                  |      |    |             |    |      |
                  | +----+----+---+     +---+----+----+ |
                  | | line card 1 |     | line card 2 | |
                  | +-------------+     +-------------+ |
                  |               device                |
                  +-------------------------------------+

    Fig. 1 Data Collection from Devices with Main-board and Line-cards

2.2.  Use Case 2: IoT Data Collection

   In the IoT data collection scenario, as shown in the following
   figure, collector usually cannot access to IoT nodes directly, but is
   isolated by the border router.  So the collector subscribes data from
   the border router, and let the border router to disassemble the
   subscription to corresponding IoT nodes.  The border router is
   typically the traffic convergence point.  It's intuitive to treat the
   border router as a broker assembling the data collected from the IoT
   nodes and forwarding to the collector[I-D.ietf-core-coap-pubsub].
   However, the border router is not so powerful on data assembling as a
   network device.  It's more efficient for the collector, which may be
   a server or even a cluster, to assemble the subscribed data if
   possible.  In this case, push servers that reside in IoT nodes can
   stream data to the collector directly while traffic only passes
   through the border router.














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                    +-------------------------------+
                    |           collector           |
                    +---^-----------^------------^--+
                        |           |            |
                        |           |            |
                        |           |            |
                        |   +-------+--------+   |
                        |   |  border router |   |
                        |   +----^------^----+   |
                        |        |      |        |
                        |        |      |        |
                        |    +---+      +---+    |
                        |    |              |    |
                    +---+----+---+      +---+----+---+
                    | IoT node 1 |      | IoT node 2 |
                    +------------+      +------------+

                        Fig. 2 IoT Data Collection

3.  Solution Overview

   All the use cases described in the previous section are very similar
   on the data subscription and publication mode, hence can be
   abstracted to the following generic distributed data collection
   framework, as shown in the following figure.

   A Collector usually includes two components,

   o  the Subscriber generates the subscription instructions to express
      what and how the collector want to receive the data;

   o  the Receiver is the target for the data publication.

   For one subscription, there may be one to many receivers.  And the
   subscriber does not necessarily share the same address with
   receivers.

   In this framework, the stream originators have the Master role and
   the Agent role.  Both the Master and the Agent include two
   components,

   o  the Subscription Server manages capabilities that it can provide
      to the subscriber.

   o  the Publication Server pushes data to the receiver according to
      the subscription information.





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   The Master knows all the capabilities that the attached Agents and
   itself can provide, and exposes the global capability to the
   Collector.  The Collector cannot see the Agents directly, so it will
   only send the subscription information to the Master.  The Master
   disassembles the subscription to multiple component subscriptions,
   each involving data from a separate telemetry source.  The component
   subscriptions are then distributed to the corresponding Agents.

   When data streaming, the Publication Server located in each stream
   originator collects and encapsulates the packets per the component
   subscription, and pushes the piece of data which it can serve
   directly to the designated data Collector.  The Collector is able to
   assemble many pieces of data associated with one subscription, and
   can also deduce the missing pieces of data.

                  +-------------------------------------+
                  |             Collector               |
                  |   +------------+   +------------+   |
                  |   | Subscriber |   |  Receiver  <-------+
                  |   +-^----+-----+   +------^-----+   |   |
                  |     |    |                |         |   |
                  +-------------------------------------+   |
             capability |    |subscription    | push        |
                        |    |                |             |
                  +-------------------------------------+   |
                  |     |    |   Master       |         |   |
                  |  +--+----v------+  +------+------+  |   |
                  |  | Subscription |  | Publication |  |   |
                  |  | Server       |  | Server      |  |   |
                  |  +--^----+------+  +-------------+  |   |
                  |     |    |                          |   |
                  +-------------------------------------+   |
             component  |    | component               push |
             capability |    | subscription                 |
                  +-------------------------------------+   |
                  |     |    |   Agent                  |   |
                  |  +--+----v------+  +-------------+  |   |
                  |  | Component    |  | Publication |  |   |
                  |  | Subscription |  | Server      +------+
                  |  | Server       |  +-------------+  |
                  |  +--------------+                   |
                  +-------------------------------------+


         Fig. 3 The Generic Distributed Data Collection Framework

   Master and Agents may interact with each other in several ways:




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   o  Agents need to have a registration or announcement handshake with
      the Master Node, so the Master Node is aware of them and of
      lifecycle events (such as Agent appearing and disappearing).

   o  The Master relays the component subscriptions to the Agents.

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

   The details of the interaction between the Master and the Agent is
   out of scope of this document.  It may be described by a dedicated
   protocol specification.

   During the subscription and the associated publication process, this
   document assumes all the Agents registered to the Mater can always
   provide the announced capabilities.

   Note: Some preliminary considerations on the solution details are now
   listed in the appendix for reference.  The detailed solution need to
   be discussed and will be added if the WG accepts the problem
   statement.

4.  IANA Considerations

   This document makes no request of IANA.

   Note to RFC Editor: this section may be removed on publication as an
   RFC.

5.  Security Considerations

6.  Acknowledgements

7.  References

7.1.  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>.



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   [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>.

   [W3C.REC-xpath-19991116]
              Clark, J. and S. DeRose, "XML Path Language (XPath)
              Version 1.0", World Wide Web Consortium Recommendation
              REC-xpath-19991116, November 1999,
              <http://www.w3.org/TR/1999/REC-xpath-19991116>.

7.2.  Informative References

   [I-D.ietf-core-coap-pubsub]
              Koster, M., Keranen, A., and J. Jimenez, "Publish-
              Subscribe Broker for the Constrained Application Protocol
              (CoAP)", draft-ietf-core-coap-pubsub-02 (work in
              progress), July 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-10 (work in progress), October 2017.

Appendix A.  Change Log

   (To be removed by RFC editor prior to publication)

Appendix B.  Subscription Decomposition

   Since Agents are invisible to the Collector, the Collector can only
   subscribe to the Master.  This requires the Master to:

   1.  expose the global capability that can be served by multiple
       stream originators;

   2.  disassemble the subscription to multiple component subscriptions,
       and distribute them to the corresponding telemetry sources.

   To achieve the above requirement, the Master need a global capability
   description which is typically the YANG [RFC7950] data model.  This
   global YANG model is provided as the contract between the Master and
   the Collector.

   The Master also need a data structure, typically a table as shown
   below, to keep track the mapping between the resource and the
   corresponding location identifier of the node that commits to serve




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   the data.  For the YANG defined capabilities, the resource is
   described using the XPath [W3C.REC-xpath-19991116] expression.

                      +------------+---------------+
                      |  resource  |  location ID  |
                      +------------+---------------+

                                  Table 1

   Each Agent associating to the Master owns a local YANG model to
   describe the capabilities which it can serve as part of the global
   capability.  All the Agents need to know the namespace associate with
   the Master.

   YANG-Push supports two filtering syntaxes which are XPath and Subtree
   [RFC6241].  When a YANG-Push subscription request arrives, the Master
   Node will firstly extract the filter information.  Consequently,
   according to the resource-locationID table, the master subscription
   can be disassembled into multiple component subscriptions, and the
   corresponding location ID can be associated.  The component
   subscriptions share the same Subscription ID as the master
   subscription.

Appendix C.  Publication Composition

   The Publication Server collects and encapsulates the packets per the
   component subscription.  There are several potential encodings,
   including XML, JSON, CBOR and GPB.  The encoding of the data records
   follows the YANG schema, so that the composition at the Receiver can
   benefit from the structured and hierarchical data instance.  The
   Collector may be able to assemble many pieces of data associated with
   one subscription, and can also deduce the missing pieces of data.

   The Collector recognizes data records associated with one
   subscription according the Subscription ID.  Data records generated
   per one subscription are assigned with the same Subscription ID.

   For the time series data stream, records are produced periodically
   from each stream originator.  The message arrival time varies because
   of the distributed nature of the publication.  The receiver assembles
   data generated at the same time period based on the recording time
   consisted in each data record.  In this case, time synchronization is
   required for all the steam originators.








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Appendix D.  Examples

   TBD

Authors' Addresses

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

   Email: zhoutianran@huawei.com


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

   Email: zhengguangying@huawei.com


   Eric Voit
   Cisco Systems
   United States of America

   Email: evoit@cisco.com


   Alexander Clemm
   Huawei
   2330 Central Expressway
   Santa Clara, California
   United States of America

   Email: alexander.clemm@huawei.com


   Andy Bierman
   YumaWorks
   United States of America

   Email: andy@yumaworks.com






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