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NETCONF Extension to support Trace Context propagation
draft-rogaglia-netconf-trace-ctx-extension-01

Document Type Active Internet-Draft (individual)
Authors Roque Gagliano , Kristian Larsson , Jan Lindblad
Last updated 2023-01-13
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draft-rogaglia-netconf-trace-ctx-extension-01
NETCONF                                                      R. Gagliano
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                              K. Larsson
Expires: 17 July 2023                                Deutsche Telekom AG
                                                             J. Lindblad
                                                           Cisco Systems
                                                         13 January 2023

         NETCONF Extension to support Trace Context propagation
             draft-rogaglia-netconf-trace-ctx-extension-01

Abstract

   This document defines how to propagate trace context information
   across the Network Configuration Protocol (NETCONF), that enables
   distributed tracing scenarios.  It is an adaption of the HTTP-based
   W3C specification.

About This Document

   This note is to be removed before publishing as an RFC.

   The latest revision of this draft can be found at TBD.  Status
   information for this document may be found at
   https://datatracker.ietf.org/doc/draft-rogaglia-netconf-trace-ctx-
   extension/.

   Discussion of this document takes place on the NETCONF Working Group
   mailing list (mailto:netconf@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/netmod/.  Subscribe at
   https://www.ietf.org/mailman/listinfo/netconf/.

   Source for this draft and an issue tracker can be found at
   https://github.com/TBD.

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/.

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   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 17 July 2023.

Copyright Notice

   Copyright (c) 2023 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
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Implementation example 1: OpenTelemetry . . . . . . . . .   4
     1.2.  Implementation example 2: YANG DataStore  . . . . . . . .   6
     1.3.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . .   7
       1.3.1.  Provisioning root cause analysis  . . . . . . . . . .   7
       1.3.2.  System performaednce profiling  . . . . . . . . . . .   8
       1.3.3.  Billing and auditing  . . . . . . . . . . . . . . . .   8
     1.4.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   8
   2.  NETCONF Extension . . . . . . . . . . . . . . . . . . . . . .   9
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   5.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Appendix A.  Changes  . . . . . . . . . . . . . . . . . . . . . .  12
     A.1.  From version 00 to 01 . . . . . . . . . . . . . . . . . .  12
   Appendix B.  TO DO List (to be deleted by RFC Editor) . . . . . .  12
   Appendix C.  XML Attributes vs RPCs input augmentations discussion
           (to be deleted by RFC Editor) . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

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1.  Introduction

   Network automation and management systems commonly consist of
   multiple sub-systems and together with the network devices they
   manage, they effectively form a distributed system.  Distributed
   tracing is a methodology implemented by tracing tools to follow,
   analyze and debug operations, such as configuration transactions,
   across multiple distributed systems.  An operation is uniquely
   identified by a trace-id and through a trace context, carries some
   metadata about the operation.  Propagating this "trace context"
   between systems enables forming a coherent view of the entire
   operation as carried out by all involved systems.

   The W3C has defined two HTTP headers for context propagation that are
   useful in use case scenarios of distributed systems like the ones
   defined in [RFC8309].  This document defines an extension to the
   NETCONF protocol to add the same concepts and enable trace context
   propagation over NETCONF.

   It is worth noting that the trace context is not meant to have any
   relationship with the data that is carried with a given operation
   (including configurations, service identifiers or state information).

   A trace context also differs from
   [I-D.lindblad-netconf-transaction-id] in several ways as the trace
   operation may involve any operation (including for example validate,
   lock, unlock, etc.)  Additionally, a trace context scope may include
   the full application stack (orchestrator, controller, devices, etc)
   rather than a single NETCONF server, which is the scope for the
   transaction-id.  The trace context is also complemetary to
   [I-D.lindblad-netconf-transaction-id] as a given trace-id can can
   associated to the different transaction-ids as part of the
   information exported to the collector.

   The following enhancement of the reference SDN Architecture from RFC
   8309 shows the impact of distributed traces for a network operator.

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                    ------------------                    -------------
                   |   Orchestrator   |                   |           |
                   |                  |     ------------> |           |
                   .------------------.                   |           |
                  .          :         .                  |           |
                 .           :          .                 | Collector |
      ------------     ------------     ------------      | (Metrics, |
     |            |   |            |   |            |     |  Events,  |
     | Controller |   | Controller |   | Controller | --> |  Logs,    |
     |            |   |            |   |            |     |  Traces)  |
      ------------     ------------     ------------      |           |
         :              .       .               :         |           |
         :             .         .              :         |           |
         :            .           .             :         |           |
    ---------     ---------   ---------     ---------     |           |
   | Network |   | Network | | Network |   | Network |    |           |
   | Element |   | Element | | Element |   | Element | -> |           |
    ---------     ---------   ---------     ---------     -------------

       Figure 1: A Sample SDN Architecture from RFC8309 augmented
         to include the export of metrics, events, logs and traces
         from the different components to a common collector.

   The network automation, management and control architectures are
   distributed in nature.  In order to "manage the managers", operators
   would like to use the same techniques as any other distributed
   systems in their IT environment.  Solutions for analysing Metrics,
   Events, Logs and Traces (M.E.L.T) are key for the successful
   monitoring and troubleshooting of such applications.  Initiatives
   such as the OpenTelemetry [OpenTelemetry] enable rich ecosystems of
   tools that NETCONF-based applications would want to participate in.

   With the implementation of this trace context propagation extension
   to NETCONF, backend systems behind the M.E.L.T collector will be able
   to correlate information from different systems but related to a
   common context.

1.1.  Implementation example 1: OpenTelemetry

   We will describe an example to show the value of trace context
   propagation in the NETCONF protocol.  In Figure 2, we show a
   deployment based on Figure 1 with a single controller and two network
   elements.  In this example, the NETCONF protocol is running between
   the Orchestrator and the Controller.  NETCONF is also used between
   the Controller and the Network Elements.

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   Let's assume an edit-config operation between the orchestrator and
   the controller that results (either synchronously or asynchronously)
   in corresponding edit-config operations from the Controller towards
   the two network elements.  All trace operations are related and will
   create M.E.L.T data.

                ------------------                         -------------
               |   Orchestrator   |    OTLP protocol       |           |
               |                  |  ------------------->  |           |
               .------------------.                        |           |
              .  NETCONF                                   |           |
             .   edit-config (trace-id "1", parent-id "A") | Collector |
    ------------                                           | (Metrics, |
   |            |                                          |  Events,  |
   | Controller |   ------------------------------------>  |  Logs,    |
   |            |                 OTLP protocol            |  Traces)  |
    ------------                                           |           |
      :      .  NETCONF                                    |           |
      :        . edit-config (trace-id "1", parent-id "B") |           |
      :          .                                         |           |
    ---------     ---------                                |           |
   | Network |   | Network |       OTLP protocol           |           |
   | Element |   | Element |  -------------------------->  |           |
    ---------     ---------                                -------------

           Figure 2: An implementation example where the NETCONF
           protocol is used between the Orchestrator and the Controller
           and also between the Controller and the Network Elements.
           Every component exports M.E.L.T information to the collector
           using the OTLP protocol.

   Each of the components in this example (Orchestrator, Controller and
   Network Elements) is exporting M.E.L.T information to the collector
   using the OpenTelemetry Protocol (OTLP).

   For every edit-config operation, the trace context is included.  In
   particular, the same trace-id "1" (simplified encoding for
   documentation) is included in all related NETCONF messages, which
   enables the collector and any backend application to correlate all
   M.E.L.T messages related to this transaction in this distributed
   stack.

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   Another interesting attribute is the parent-id.  We can see in this
   example that the parent-id between the orchestrator and the
   controller ("A") is different from the one between the controller and
   the network elements ("B").  This attribute will help the collector
   and the backend applications to build a connectivity graph to
   understand how M.E.L.T information exported from one component
   relates to the information exported from a different component.

   With this additional metadata exchanged between the components and
   exposed to the M.E.L.T collector, there are important improvements to
   the monitor and troubleshooting operations for the full application
   stack.

1.2.  Implementation example 2: YANG DataStore

   OpenTelemetry implements the "push" model for data streaming where
   information is sent to the back-end as soon as produced and is not
   required to be stored in the system.  In certain cases, a "pull"
   model may be envisioned, for example for performing forensic analysis
   while not all OTLP traces are available in the back-end systems.

   An implementation of a "pull" mechanism for M.E.L.T. information in
   general and for traces in particular, could consist of storying
   traces in a yang datastore (particularly the operational datastore.)
   Implementations should consider the use of circular buffers to avoid
   resources exhaustion.  External systems could access traces (and
   particularly past traces) via NETCONF, RESTCONF, gNMI or other
   polling mechanisms.  Finally, storying traces in a YANG datastore
   enables the use of YANG-Push [RFC8641] or gNMI Telemetry as an
   additional "push" mechanisms.

   This document does not specify the YANG module in which traces could
   be stored inside the different components.  That said, storing the
   context information described in this document as part of the
   recorded traces would allow back-end systems to correlate the
   information from different components as in the OpenTelemetry
   implementation.

   Note to be removed in the future: Some initial ideas are under
   discussion in the IETF for defining a standard YANG data model for
   traces.  For example see: I-D.quilbeuf-opsawg-configuration-tracing
   which focusses only on configuration change root cause analysis use
   case (see bellow the use case desciption.).  This ideas are
   complementary to this draft.

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                ------------------                         -------------
               | Orchestrator     |                        |           |
               |                  |    NC/RC/gNMI or YP    |           |
               |   YANG DataStore | <------------------->  |           |
               .------------------.     pull or push       |           |
              .  NETCONF                                   |           |
             .   edit-config (trace-id "1", parent-id "A") | Collector |
    ----------------                                       | (Metrics, |
   |                |           NC/RC/gNMI or YP           |  Events,  |
   | Controller     |   -------------------------------->  |  Logs,    |
   |  YANG DataStore|             pull or push             |  Traces)  |
    ----------------                                       |           |
      :      .  NETCONF                                    |           |
      :        . edit-config (trace-id "1", parent-id "B") |           |
      :          .                                         |           |
    ---------     ---------                                |           |
   | Network |   | Network |        NC/RC/gNMI or YP       |           |
   | Element |   | Element |  -------------------------->  |           |
   |   YG DS |   |   YG DS |         pull or push          |           |
    ---------     ---------                                -------------

           Figure 3: An implementation example where the NETCONF
           protocol is used between the Orchestrator and the Controller
           and also between the Controller and the Network Elements.
           M.E.L.T. information is stored in local Yang Datastores and
           accessed by the collector using "pull" mechanisms using the
           NETCONF (NC), RESTCONF (RC) or gNMI protocols. A "push"
           strategy is also possible via YANG-Push or gNMI.

1.3.  Use Cases

1.3.1.  Provisioning root cause analysis

   When a provisioning activity fails, errors are typically propagated
   northbound, however this information may be difficult to troubleshoot
   and typically, operators are required to navigate logs across all the
   different components.

   With the support for trace context propagation as described in this
   document for NETCONF, the collector will be able to search every
   trace, event, metric, or log in connection to that trace-id and
   faciliate the performance of a root cause analysis due to a network
   changes.  The trace information could also include as an optional
   resource the different NETCONF transaction ids described in
   [I-D.lindblad-netconf-transaction-id].

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1.3.2.  System performaednce profiling

   When operating a distributed system such as the one shown in
   Figure 2, operators are expected to benchmark what are the Key
   Performance Indicators (KPIs) for the most common tasks.  For
   example, what is the typical delay when provisioning a VPN service
   across different controllers and devices.

   Thanks to Application Performance Management (APM) systems, from
   these KPIs, an operator can detect a normal and abnormal behaviour of
   the distributed system.  Also, an operator can better plan any
   upgrades or enhancements in the platform.

   With the support for context propagation as described in this
   document for NETCONF, much richer system-wide KPIs can be defined and
   used for troubleshooting as the metrics and traces propagated by the
   different components share a common context.  Troubleshooting for
   abnormal behaviours can also be troubleshot from the system view down
   to the individual element.

1.3.3.  Billing and auditing

   In certain circuntances, we could perceive that tracing infomration
   could be used as additional inputs to billing systems.  In
   particular, trace context information could be used to validate that
   a certain northbound order was carried out in southbound systems.

1.4.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
   NOT","SHOULD","SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY",
   and "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   The XML prefixes used in this document are mapped as follows:

   *  xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0",

   *  xmlns:notif="urn:ietf:params:xml:ns:netconf:notification:1.0",

   *  xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-patch" and

   *  xmlns:ypatch="urn:ietf:params:xml:ns:yang:ietf-yang-patch".

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2.  NETCONF Extension

   When performing NETCONF operations by sending NETCONF RPCs, a NETCONF
   client MAY include trace context information in the form of XML
   attributes.  The [W3C-Trace-Context] defines two HTTP headers;
   traceparent and tracestate for this purpose.  NETCONF clients that
   are taking advantage of this feature MUST add one w3ctc:traceparent
   attribute to the nc:rpc tag.

   A NETCONF server that receives a trace context attribute in the form
   of a w3ctc:traceparent attribute SHOULD apply the mutation rules
   described in [W3C-Trace-Context].  A NETCONF server MAY add one
   w3ctc:traceparent attribute in the nc:rpc-reply response to the
   nc:rpc tag above.  NETCONF servers MAY also add one w3ctc:traceparent
   attribute in notification and update message envelopes:
   notif:notification, yp:push-update and yp:push-change-update.

   For example, a NETCONF client might send:

   <rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="1"
        xmlns:w3ctc="urn:ietf:params:xml:ns:netconf:w3ctc:1.0"
        w3ctc:traceparent=
          "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01">
     <get-config/>
   </rpc>

   In all cases above where a client or server adds a w3ctc:traceparent
   attribute to a tag, that client or server MAY also add one
   w3ctc:tracestate attribute to the same tag.

   The proper encoding and interpretation of the contents of the
   w3ctc:traceparent attribute is described in [W3C-Trace-Context]
   section 3.2 except 3.2.1.  The proper encoding and interpretation of
   the contents in the w3ctc:tracestate attribute is described in
   [W3C-Trace-Context] section 3.3 except 3.3.1 and 3.3.1.1.  A NETCONF
   tag can only have zero or one w3ctc:tracestate attributes, so its
   content MUST always be encoded as a single string.  The tracestate
   field value is a list of list-members separated by commas (,).  A
   list-member is a key/value pair separated by an equals sign (=).
   Spaces and horizontal tabs surrounding list-members are ignored.
   There is no limit to the number of list-members in a list.

   For example, a NETCONF client might send:

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   <rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="1"
        xmlns:w3ctc="urn:ietf:params:xml:ns:netconf:w3ctc:1.0"
        w3ctc:tracestate="rojo=00f067aa0ba902b7,congo=t61rcWkgMzE"
        w3ctc:traceparent=
          "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01">
     <get-config/>
   </rpc>

   As in all XML documents, the order between the attributes in an XML
   tag has no significance.  Clients and servers MUST be prepared to
   handle the attributes no matter in which order they appear.  The
   tracestate value MAY contain double quotes in its payload.  If so,
   they MUST be encoded according to XML rules, for example:

   <rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="1"
        xmlns:w3ctc="urn:ietf:params:xml:ns:netconf:w3ctc:1.0"
        w3ctc:traceparent=
          "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01"
        w3ctc:tracestate=
          "value-with-quotes=&quot;Quoted string&quot;,other-value=123">
     <get-config/>
   </rpc>

   TBD Errors ....

3.  Security Considerations

   TODO Security

4.  IANA Considerations

   This document registers the following capability identifier URN in
   the 'Network Configuration Protocol (NETCONF) Capability URNs'
   registry:

     urn:ietf:params:netconf:capability:w3ctc:1.0

   This document registers one XML namespace URN in the 'IETF XML
   registry', following the format defined in [RFC3688]
   (https://tools.ietf.org/html/rfc3688).

     URI: urn:ietf:params:xml:ns:netconf:w3ctc:1.0

     Registrant Contact: The NETCONF WG of the IETF.

     XML: N/A, the requested URI is an XML namespace.

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5.  Acknowledgments

   TBD

6.  References

6.1.  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>.

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

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [W3C-Trace-Context]
              "W3C Recommendation on Trace Context", 23 November 2021,
              <https://www.w3.org/TR/2021/REC-trace-context-
              1-20211123/>.

6.2.  Informative References

   [I-D.lindblad-netconf-transaction-id]
              Lindblad, J., "Transaction ID Mechanism for NETCONF", Work
              in Progress, Internet-Draft, draft-lindblad-netconf-
              transaction-id-02, 8 June 2022,
              <https://www.ietf.org/archive/id/draft-lindblad-netconf-
              transaction-id-02.txt>.

   [OpenTelemetry]
              "OpenTelemetry Cloud Native Computing Foundation project",
              29 August 2022, <https://opentelemetry.io>.

   [RFC8309]  Wu, Q., Liu, W., and A. Farrel, "Service Models
              Explained", RFC 8309, DOI 10.17487/RFC8309, January 2018,
              <https://www.rfc-editor.org/info/rfc8309>.

   [RFC8641]  Clemm, A. and E. Voit, "Subscription to YANG Notifications
              for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641,
              September 2019, <https://www.rfc-editor.org/info/rfc8641>.

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   [W3C-Baggage]
              "W3C Propagation format for distributed context Baggage",
              23 November 2021,
              <https://www.w3.org/TR/baggage/#examples-of-http-headers>.

Appendix A.  Changes

A.1.  From version 00 to 01

   *  Added new section: Implementation example 2: YANG DataStore

   *  Added new use case: Billing and auditing

   *  Added in introduction and in "Provisioning root cause analysis"
      the idea that the different transaction-ids defined in
      [I-D.lindblad-netconf-transaction-id] could be added as part of
      the tracing information to be exported to the collectors, showing
      how the two documents are complementary.

Appendix B.  TO DO List (to be deleted by RFC Editor)

   *  Manage versioning of the trace-context specification

   *  Error handling specification

   *  We intend to extend the trace-concext capability to RESTCONF in a
      future draft

   *  The W3C is working on a draft document to introduce the concept of
      "baggage" [W3C-Baggage] that we expect part of a future draft for
      NETCONF and RESTCONF

Appendix C.  XML Attributes vs RPCs input augmentations discussion (to
             be deleted by RFC Editor)

   There are arguments that can be raised regarding using XML Attribute
   or to augment NETCONF RPCs.

   We studied Pros/Cons of each option and decided to propose XML
   attributes:

   XML Attributes Pro:

   *  Literal alignment with W3C specification

   *  Same encoding for RESTCONF and NETCONF enabling code reuse

   *  One specification for all current and future rpcs

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   XML Attributes Cons:

   *  No YANG modeling, multiple values represented as a single string

   *  Dependency on W3C for any extension or changes in the future as
      encoding will be dictated by string encoding

   RPCs Input Augmentations Pro:

   *  YANG model of every leaf

   *  Re-use of YANG toolkits

   *  Simple updates by augmentations on existing YANG module

   *  Possibility to express deviations in case of partial support

   RPCs Input Augmentations Cons:

   *  Need to augment every rpc, including future rpcs would need to
      consider these augmentations, which is harder to maintain

   *  There is no literal alignment with W3C standard.  However, as
      mentioned before most of the time there will be modifications to
      the content

   *  Would need updated RFP for each change at W3C, which will make
      adoption of new features slower

Authors' Addresses

   Roque Gagliano
   Cisco Systems
   Avenue des Uttins 5
   CH-1180 Rolle
   Switzerland
   Email: rogaglia@cisco.com

   Kristian Larsson
   Deutsche Telekom AG
   Email: kll@dev.terastrm.net

   Jan Lindblad
   Cisco Systems
   Email: jlindbla@cisco.com

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