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Toward a Network Telemetry Framework
draft-song-ntf-01

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This is an older version of an Internet-Draft whose latest revision state is "Replaced".
Authors Haoyu Song , Tianran Zhou , Zhenbin Li
Last updated 2018-03-19
Replaced by draft-song-opsawg-ntf
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draft-song-ntf-01
Network Working Group                                       H. Song, Ed.
Internet-Draft                                                   T. Zhou
Intended status: Informational                                     Z. Li
Expires: September 19, 2018                                       Huawei
                                                          March 18, 2018

                  Toward a Network Telemetry Framework
                           draft-song-ntf-01

Abstract

   This document suggests the necessity for an architectural framework
   to address network telemetry and articulates the categories and
   components of such a framework.  The requirements, challenges,
   existing solutions, and future directions are discussed for each
   category of the framework.  The framework for network telemetry helps
   to set some common ground for the collection of related works and put
   future developments into perspective.

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 19, 2018.

Copyright Notice

   Copyright (c) 2018 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.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology and Abbreviations . . . . . . . . . . . . . .   4
     1.3.  Network Telemetry . . . . . . . . . . . . . . . . . . . .   5
   2.  The Necessity of a Network Telemetry Framework  . . . . . . .   6
   3.  Network Telemetry Framework . . . . . . . . . . . . . . . . .   7
     3.1.  Existing Works Mapped in the Framework  . . . . . . . . .   9
     3.2.  Management Plane Telemetry  . . . . . . . . . . . . . . .  10
       3.2.1.  Requirements and Challenges . . . . . . . . . . . . .  10
       3.2.2.  Push Extensions for NETCONF . . . . . . . . . . . . .  11
       3.2.3.  gRPC Network Management Interface . . . . . . . . . .  11
     3.3.  Control Plane Telemetry . . . . . . . . . . . . . . . . .  12
       3.3.1.  Requirements and Challenges . . . . . . . . . . . . .  12
       3.3.2.  BGP Monitoring Protocol . . . . . . . . . . . . . . .  12
     3.4.  Data Plane Telemetry  . . . . . . . . . . . . . . . . . .  12
       3.4.1.  Requirements and Challenges . . . . . . . . . . . . .  12
       3.4.2.  Dynamic Network Probe . . . . . . . . . . . . . . . .  13
       3.4.3.  IP Flow Information Export (IPFIX) protocol . . . . .  13
       3.4.4.  In-Situ OAM . . . . . . . . . . . . . . . . . . . . .  13
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  14
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  14
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Motivation

   An intent-driven automated network is the logical next step for
   network evolution, aiming to reduce human labor, make the most
   efficient use of network resources, and provide better services more
   aligned with customer requirements.  Tools based on machine learning
   technologies and big data analytics are powerful for fault detection
   and isolation, identification of anomalies to normal behaviors,

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   patterns, and policy violation detection.  Some tools can even
   predict future events based on historical data.  The observation and
   inference from collected network data can help guide network policy
   updates for planning, intrusion prevention, optimization, and self-
   healing.  A closed control loop is therefore achieved.

1.1.  Use Cases

   Specifically, we have identified a few key network OAM use cases that
   network operators need the most.  All these use cases involves the
   data extracted from the network data plane and sometimes from the
   network control plane and management plane:

   Policy Compliance:  Network policies are the rules that constraint
      the services for network access, provide differentiate within a
      service, or enforce specific treatment on the traffic.  For
      example, a service function chain is a policy that requires the
      selected flows to pass through a set of network functions in
      order.  While a policy is enforced, the compliance needs to be
      monitored continuously.

   SLA Compliance:  A service-level agreement defines the level of
      service a user expects from a network operator, which include the
      metrics for the service measurement and remedy/penalty procedures
      when the service level misses the agreement.  Users need to check
      if they get the service as promised and network operators need to
      evaluate how they can deliver the services that can meet the
      Service Level Agreement (SLA).

   Root Cause Analysis:  Network failure often involves a sequence of
      chained events and the source of the failure is not
      straightforward to identify, especially when the failure is
      sporadic.  While machine learning or other data analytics
      technologies can be used for root cause analysis, it up to the
      network to provide all the relevant data for analysis.

   Load Balancing and Traffic Engineering:  Network operators are
      motivated to optimize their network utilization for better ROI or
      lower CAPEX, as well as differentiation across services and/or
      users of a given service.  The first step is to know the real-time
      network conditions before applying policies to steer the user
      traffic or adjust the load balancing algorithm.  In some cases
      network micro-bursts need to be detected in a very short time-
      frame so that fine grained traffic control can be applied to avoid
      possible network congestion.

   Packet Drop Detection:  Sporadic packet drops in networks are
      notoriously hard to locate and debug.  Network operators are

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      plagued by the lack of tools that can identify the packet drop
      locations and reasons.  Both active and passive measurements are
      not very effective in solving this problem.

   These use cases show that the conventional OAM techniques are not
   enough for the following reasons:

   o  Most use cases need to continuously monitor the network and
      dynamically refine the data collection in real-time.  The poll-
      based low-frequency data collection is ill-suited for these
      applications.  Streaming data directly pushed from the data source
      is preferred.

   o  Various data is needed from any place ranging from the packet
      processing engine to the QoS traffic manager.  Traditional data
      plane devices cannot provide the necessary probes.  An open and
      programmable data plane is therefore needed.

   o  Many application scenarios need to correlate data from multiple
      sources (e.g., from distributed nodes or from different network
      plane).  A piecemeal solution is often lacking the capability to
      consolidate the data from multiple sources.  The composition of a
      complete solution can be guided by a comprehensive framework.

   o  The passive measurement techniques can either consume too much
      network resources and render too much redundant data, or lead to
      inaccurate results.  The active measurement techniques are
      indirect, and they can interfere with the user traffic.  We need
      techniques that can collect direct and on-demand data from user
      traffic.

1.2.  Terminology and Abbreviations

   AI:  Artificial Intelligence.  Use machine-learning based
      technologies to automate network operation.

   BMP:  BGP Monitoring Protocol

   DNP:  Dynamic Network Probe

   gNMI:  gPRC Network Managment Interface

   gRPC:  gRPC Remote Procesure Call

   IDN:  Intent-Driven Network

   IPFIX:  IP Flow Information Export Protocol

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   IPFPM:  IP Flow Performance Measurement

   IOAM:  In-situ OAM

   NETCONF:  Network Configuration Protocol

   Network Telemetry:  A general term for techniques to gain network
      visibility, through network data collection for analysis and
      measurement.

   NMS:  Network Management System

   OAM:  Operations, Administration, and Maintenance.  A group of
      network management functions that provide network fault
      indication, fault localization, performance information, and data
      and diagnosis functions.

   SNMP:  Simple Network Managment Protocol

   YANG:  A data modeling language for NETCONF

   YANG FSM:  A YANG model to define device side finite state machine

   YANG PUSH:  A method to subscribe pushed data from remote YANG
      datastore

1.3.  Network Telemetry

   For a long time, network OAM applications have relied upon protocols
   such as SNMP [RFC1157] to monitor the network.  SNMP can only provide
   limited information about the network.  Since SNMP is poll-based, it
   incurs low data rate and high processing overhead.  Such drawbacks
   make SNMP unsuitable for today's automatic network applications.

   Network telemetry has emerged as a mainstream technical term to refer
   to the newer technologies of data collection and consumption in the
   IDN paradigm, distinguishing itself form the convention technologies
   for network OAM.  It is expected that network telemetry can provide
   the necessary network visibility for automatic network OAM, address
   the shortcomings of conventional technologies, and allow for the
   emergence of new technologies.

   Although the network telemetry technologies continue to evolve,
   several defining characteristics of network telemetry have been well
   accepted:

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   o  Instead of polling data from network devices, the telemetry
      collector subscribes to the streaming data pushed from the data
      source in network devices.

   o  The data is normalized and encoded efficiently for export.

   o  The data is model-based which allows applications to configure and
      consume data with ease.

   In addition, we believe the ideal network telemetry solution should
   also support the following features:

   o  The data can be customized at runtime to cater to the specific
      need of applications.  This needs the support of a programmable
      data plane which allows probes to be deployed at flexible
      locations.

   o  The data for a single application can come from multiple data
      sources (e.g., cross domain, cross device, and cross layer) and
      needs to be correlated to take effect.

2.  The Necessity of a Network Telemetry Framework

   Big data analytics and machine-learning based AI technologies are
   applied for network OAM, relying on abundant data from networks.  The
   single-sourced and static data acquisition cannot meet the data
   requirements.  It is desirable to have a framework that integrates
   multiple telemetry approaches from different layers, and allows
   flexible combinations for different applications.  The framework will
   benefit application development for the following reasons.

   o  Network visibility presents multiple viewpoints.  For example, the
      device viewpoint takes the network infrastructure as the
      monitoring object from which the network topology and device
      status can be acquired; the traffic viewpoint takes the flows or
      packets as the monitoring object from which the traffic quality
      and path can be acquired.  An application may need to switch its
      viewpoint during operation.  It may also need to correlate a
      service and its network experience to acquire the comprehensive
      information.

   o  Applications require network telemetry to be elastic in order to
      efficiently use the network resource and reduce the performance
      impact.  Routine network monitoring covers the entire network with
      low data sampling rate.  When issues arise or trends emerge, the
      telemetry data source can be refocused and the data rate can be
      boosted.

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   o  Efficient data fusion is critical for applications to reduce the
      overall quantity of data and improve the accuracy of analysis.

   So far, some telemetry related work has been done within IETF.
   However, this work is fragmented and scattered in different working
   groups.  The lack of coherence makes it difficult to assemble a
   comprehensive network telemetry system and causes repetitive and
   redundant work.

   A formal network telemetry framework is needed for constructing a
   working system.  The framework should cover the concepts and
   components from the standardization perspective.  This document
   clarifies the layers on which the telemetry is exerted and decomposes
   the telemetry system into a set of distinct components that the
   existing and future work can easily map to.

3.  Network Telemetry Framework

   Telemetry can be applied on the data plane, the control plane, and
   the management plane in a network, as shown in Figure 1.

                   +------------------------------+
                   |                              |
                   |      OAM Applications        |
                   |                              |
                   +------------------------------+
                        ^      ^           ^
                        |      |           |
                        V      |           V
                   +-----------|---+--------------+
                   |           |   |              |
                   | Control Pl|ane|              |
                   | Telemetry | <--->            |
                   |           |   |              |
                   |      ^    V   |  Management  |
                   +------|--------+  Plane       |
                   |      V        |  Telemetry   |
                   |               |              |
                   | Data Plane  <--->            |
                   | Telemetry     |              |
                   |               |              |
                   +---------------+--------------+

        Figure 1: Layer Category of the Network Telemetry Framework

   Note that the interaction with OAM applications can be indirect.  For
   example, in the management plane telemetry, the management plane may

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   need to acquire data from the data plane.  On the other hand, an OAM
   application may involve more than one plane simultaneously.  For
   example, an SLA compliance application may require both the data
   plane telemetry and the control plane telemetry.

   At each plane, the telemetry can be further partitioned into five
   distinct components:

   Data Source:  Determine where the original data is acquired.  The
      data source usually just provides raw data which needs further
      processing.  A data source can be considered a probe.  A probe can
      be statically installed or dynamically installed.

   Data Subscription:  Determine the protocol and channel for
      applications to acquire desired data.  Data subscription is also
      responsible to define the desired data that might not be directly
      available form data sources.  The subscription data can be
      described by a model.  The model can be statically installed or
      dynamically installed.

   Data Generation:  The original data needs to be processed, encoded,
      and formatted in network devices to meet application subscription
      requirements.  This may involve in-network computing and
      processing on either the fast path or the slow path in network
      devices.

   Data Export:  Determine how the ready data are delivered to
      applications.

   Data Analysis:  In this final step, data is consumed by applications.
      Data analysis can be interactive.  It may initiate further data
      subscription.

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                   +------------------------------+
                   |                              |
                   |      Data Analysis           |
                   |                              |
                   +------------------------------+
                           |               ^
                           |               |
                           V               |
                   +---------------+--------------+
                   |               |              |
                   | Data          | Data         |
                   | Subscription  | Export       |
                   |               |              |
                   +---------------+--------------|
                   |                              |
                   |       Data Generation        |
                   |                              |
                   +------------------------------|
                   |                              |
                   |       Data Source            |
                   |                              |
                   +------------------------------+

          Figure 2: Components in the Network Telemetry Framework

   Since most existing standard-related work belongs to the first four
   components, in the remainder of the document, we focus on these
   components only.

3.1.  Existing Works Mapped in the Framework

   The following table provides a non-exhaustive list of existing works
   (mainly published in IETF and with the emphasis on the latest new
   technologies) and shows their positions in the framework.

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            +-----------+--------------+---------------+--------------+
            |           | Management   | Control       | Data         |
            |           | Plane        | Plane         | Plane        |
            +-----------+--------------+---------------+--------------+
            |           | YANG Data    | Control Proto.| Flow/Packet  |
            | Data      | Store        | Network State | Statistics   |
            | Source    |              |               | States       |
            |           |              |               |              |
            +-----------+--------------+---------------+--------------+
            |           | gPRC         | NETCONF/YANG  | NETCONF/YANG |
            | Data      | YANG PUSH    | BGP           | YANG FSM     |
            | Subscribe |              |               |              |
            |           |              |               |              |
            +-----------+--------------+---------------+--------------+
            |           | Soft DNP     | Soft DNP      | In-situ OAM  |
            | Data      |              |               | IPFPM        |
            | Generation|              |               | Hard DNP     |
            |           |              |               |              |
            +-----------+--------------+---------------+--------------+
            |           | gRPC         | BMP           | IPFIX        |
            | Data      | YANG PUSH    |               | UDP          |
            | Export    | UDP          |               |              |
            |           |              |               |              |
            +-----------+--------------+---------------+--------------+

                          Figure 3: Existing Work

3.2.  Management Plane Telemetry

3.2.1.  Requirements and Challenges

   The management plane of the network element interacts with the
   Network Management System (NMS), and provides information such as
   performance data, network logging data, network warning and defects
   data, and network statistics and state data.  Some legacy protocols
   are widely used for the management plane, such as SNMP and Syslog,
   but these protocols do not meet the requirements of the automatic
   network OAM applications.

   New management plane telemetry protocols should consider the
   following requirements:

   Convenient Data Subscription:  An application should have the freedom
      to choose the data export means such as the data types and the
      export frequency.

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   Structured Data:  For automatic network OAM, machines will replace
      human for network data comprehension.  The schema languages such
      as YANG can efficiently describe structured data and normalize
      data encoding and transformation.

   High Speed Data Transport:  In order to retain the information, a
      server needs to send a large amount of data at high frequency.
      Compact encoding formats are needed to compress the data and
      improve the data transport efficiency.  The push mode, by
      replacing the poll mode, can also reduce the interactions between
      clients and servers, which help to improve the server's
      efficiency.

3.2.2.  Push Extensions for NETCONF

   NETCONF [RFC6241] is one popular network management protocol, which
   is also recommended by IETF.  Although it can be used for data
   collection, NETCONF is good at configurations.  YANG Push
   [I-D.ietf-netconf-yang-push] extends NETCONF and enables subscriber
   applications to request a continuous, customized stream of updates
   from a YANG datastore.  Providing such visibility into changes made
   upon YANG configuration and operational objects enables new
   capabilities based on the remote mirroring of configuration and
   operational state.  Moreover, distributed data collection mechanism
   [I-D.zhou-netconf-multi-stream-originators] via UDP based publication
   channel [I-D.ietf-netconf-udp-pub-channel] provides enhanced
   efficiency for the NETCONF based telemetry.

3.2.3.  gRPC Network Management Interface

   gRPC Network Management Interface (gNMI)
   [I-D.openconfig-rtgwg-gnmi-spec] is a network management protocol
   based on the gRPC [I-D.kumar-rtgwg-grpc-protocol] RPC (Remote
   Procedure Call) framework.  With a single gRPC service definition,
   both configuration and telemetry can be covered. gRPC is an HTTP/2
   [RFC7540] based open source micro service communication framework.
   It provides a number of capabilities that makes it well-suited for
   network telemetry, including:

   o  Full-duplex streaming transport model combined with a binary
      encoding mechanism provided further improved telemetry efficiency.

   o  gRPC provides higher-level features consistency across platforms
      that common HTTP/2 libraries typically do not.  This
      characteristic is especially valuable for the fact that telemetry
      data collectors normally reside on a large variety of platforms.

   o  The built-in load-balancing and failover mechanism.

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3.3.  Control Plane Telemetry

3.3.1.  Requirements and Challenges

   The control plane runs the routing protocol (e.g., BGP, OSPF, and IS-
   IS) to calculate the routing table for a network device.  The control
   plane telemetry monitors the routing protocols to ensure they are
   working properly.

3.3.2.  BGP Monitoring Protocol

   BGP Monitoring Protocol (BMP) [RFC7854] is used to monitor BGP
   sessions and intended to provide a convenient interface for obtaining
   route views.  The data is collected from the Adjacency-RIB-In routing
   tables, which are the pre-policy tables, meaning that the routes in
   these tables have not been filtered or modified by routing policies.
   So the monitoring station can receive all routes, not just the active
   routes.

3.4.  Data Plane Telemetry

3.4.1.  Requirements and Challenges

   An effective data plane telemetry system relies on the data that the
   network device can expose.  The data's quality, quantity, and
   timeliness must meet some stringent requirements.  This raises some
   challenges to the network data plane devices where the first hand
   data originate.

   o  A data plane device's main function is user traffic processing and
      forwarding.  While supporting network visibility is important, the
      telemetry is just an auxiliary function and it should not impede
      normal traffic processing and forwarding (i.e., the performance is
      not lowered and the behavior is not altered due to the telemetry
      functions).

   o  The network OAM applications requires end-to-end visibility from
      various sources, which results in a huge volume of data.  However,
      the sheer data quantity should not stress the network bandwidth,
      regardless of the data delivery approach (i.e., through in-band or
      out-of-band channels).

   o  The data plane devices must provide the data in a timely manner
      with the minimum possible delay.  Long processing, transport,
      storage, and analysis delay can impact the effectiveness of the
      control loop and even render the data useless.

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   o  The data should be structured and labeled, and easy for
      applications to parse and consume.  At the same time, the data
      types needed by applications can vary significantly.  The data
      plane devices need to provide enough flexibility and
      programmability to support the precise data provision for
      applications.

   o  The data plane telemetry should support incremental deployment and
      work even though some devices are unaware of the system.  This
      challenge is highly relevant to the standards and legacy networks.

3.4.2.  Dynamic Network Probe

   Hardware based Dynamic Network Probe (DNP) [I-D.song-opsawg-dnp4iq]
   provides a programmable means to customize the data that an
   application collects from the data plane.  A direct benefit of DNP is
   the reduction of the exported data.  A full DNP solution covers
   several components including data source, data subscription, and data
   generation.  The data subscription needs to define the custom data
   which can be composed and derived from the raw data sources.  The
   data generation takes advantage of the moderate in-network computing
   to produce the desired data.

   While DNP can introduce unforeseeable flexibility to the data plane
   telemetry, it also faces some challenges.  It requires a flexible
   data plane that can be dynamically reprogrammed at runtime.  The
   programming API is yet to be defined.

3.4.3.  IP Flow Information Export (IPFIX) protocol

   Traffic on a network can be seen as a set of flows passing through
   network elements.  IP Flow Information Export (IPFIX) [RFC7011]
   provides a means of transmitting traffic flow information for
   administrative or other purposes.  A typical IPFIX enabled system
   includes a pool of Metering Processes collects data packets at one or
   more Observation Points, optionally filters them and aggregates
   information about these packets.  An Exporter then gathers each of
   the Observation Points together into an Observation Domain and sends
   this information via the IPFIX protocol to a Collector.

3.4.4.  In-Situ OAM

   Traditional passive and active monitoring and measurement techniques
   are either inaccurate or resource-consuming.  It is preferable to
   directly acquire data associated with a flow's packets when the
   packets pass through a network.  In-situ OAM (iOAM)
   [I-D.brockners-inband-oam-requirements], a data generation technique,
   embeds a new instruction header to user packets and the instruction

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   directs the network nodes to add the requested data to the packets.
   Thus, at the path end the packet's experience on the entire
   forwarding path can be collected.  Such firsthand data is invaluable
   to many network OAM applications.

   However, iOAM also faces some challenges.  The issues on performance
   impact, security, scalability and overhead limits, encapsulation
   difficulties in some protocols, and cross-domain deployment need to
   be addressed.

4.  Security Considerations

   TBD

5.  IANA Considerations

   This document includes no request to IANA.

6.  Contributors

   The other contributors of this document are listed as follows.

   o  Yunan Gu, Huawei

   o  James N.  Guichard, Huawei

7.  Acknowledgments

   TBD.

8.  References

8.1.  Normative References

   [RFC1157]  Case, J., Fedor, M., Schoffstall, M., and J. Davin,
              "Simple Network Management Protocol (SNMP)", RFC 1157,
              DOI 10.17487/RFC1157, May 1990,
              <https://www.rfc-editor.org/info/rfc1157>.

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

   [RFC7540]  Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
              Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
              DOI 10.17487/RFC7540, May 2015,
              <https://www.rfc-editor.org/info/rfc7540>.

   [RFC7854]  Scudder, J., Ed., Fernando, R., and S. Stuart, "BGP
              Monitoring Protocol (BMP)", RFC 7854,
              DOI 10.17487/RFC7854, June 2016,
              <https://www.rfc-editor.org/info/rfc7854>.

8.2.  Informative References

   [I-D.brockners-inband-oam-requirements]
              Brockners, F., Bhandari, S., Dara, S., Pignataro, C.,
              Gredler, H., Leddy, J., Youell, S., Mozes, D., Mizrahi,
              T., <>, P., and r. remy@barefootnetworks.com,
              "Requirements for In-situ OAM", draft-brockners-inband-
              oam-requirements-03 (work in progress), March 2017.

   [I-D.ietf-netconf-udp-pub-channel]
              Zheng, G., Zhou, T., and A. Clemm, "UDP based Publication
              Channel for Streaming Telemetry", draft-ietf-netconf-udp-
              pub-channel-02 (work in progress), March 2018.

   [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-15 (work in
              progress), February 2018.

   [I-D.kumar-rtgwg-grpc-protocol]
              Kumar, A., Kolhe, J., Ghemawat, S., and L. Ryan, "gRPC
              Protocol", draft-kumar-rtgwg-grpc-protocol-00 (work in
              progress), July 2016.

   [I-D.openconfig-rtgwg-gnmi-spec]
              Shakir, R., Shaikh, A., Borman, P., Hines, M., Lebsack,
              C., and C. Morrow, "gRPC Network Management Interface
              (gNMI)", draft-openconfig-rtgwg-gnmi-spec-01 (work in
              progress), March 2018.

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   [I-D.song-opsawg-dnp4iq]
              Song, H. and J. Gong, "Requirements for Interactive Query
              with Dynamic Network Probes", draft-song-opsawg-dnp4iq-01
              (work in progress), June 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-01 (work in progress),
              November 2017.

Authors' Addresses

   Haoyu Song (editor)
   Huawei
   2330 Central Expressway
   Santa Clara
   USA

   Email: haoyu.song@huawei.com

   Tianran Zhou
   Huawei
   156 Beiqing Road
   Beijing, 100095
   P.R. China

   Email: zhoutianran@huawei.com

   Zhenbin Li
   Huawei
   156 Beiqing Road
   Beijing, 100095
   P.R. China

   Email: lizhenbin@huawei.com

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