



Internet Engineering Task Force (IETF)                         G. Mirsky
Request for Comments: 9551                                      Ericsson
Category: Informational                                     F. Theoleyre
ISSN: 2070-1721                                                     CNRS
                                                         G. Papadopoulos
                                                          IMT Atlantique
                                                           CJ. Bernardos
                                                                    UC3M
                                                                B. Varga
                                                               J. Farkas
                                                                Ericsson
                                                              March 2024


   Framework of Operations, Administration, and Maintenance (OAM) for
                   Deterministic Networking (DetNet)

Abstract

   Deterministic Networking (DetNet), as defined in RFC 8655, aims to
   provide bounded end-to-end latency on top of the network
   infrastructure, comprising both Layer 2 bridged and Layer 3 routed
   segments.  This document's primary purpose is to detail the specific
   requirements of the Operations, Administration, and Maintenance (OAM)
   recommended to maintain a deterministic network.  The document will
   be used in future work that defines the applicability of and
   extension of OAM protocols for a deterministic network.  With the
   implementation of the OAM framework in DetNet, an operator will have
   a real-time view of the network infrastructure regarding the
   network's ability to respect the Service Level Objective (SLO), such
   as packet delay, delay variation, and packet-loss ratio, assigned to
   each DetNet flow.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are candidates for any level of Internet
   Standard; see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9551.

Copyright Notice

   Copyright (c) 2024 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
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   publication of this document.  Please review these documents
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   in the Revised BSD License.

Table of Contents

   1.  Introduction
     1.1.  Definitions
     1.2.  Requirements Language
   2.  Role of OAM in DetNet
   3.  Operation
     3.1.  Information Collection
     3.2.  Continuity Check
     3.3.  Connectivity Verification
     3.4.  Route Tracing
     3.5.  Fault Verification/Detection
     3.6.  Fault Localization and Characterization
     3.7.  Use of Hybrid OAM in DetNet
   4.  Administration
     4.1.  Collection of Metrics
     4.2.  Worst-Case Metrics
   5.  Maintenance
     5.1.  Replication/Elimination
     5.2.  Resource Reservation
   6.  Requirements
     6.1.  For the DetNet Forwarding Sub-layer
     6.2.  For the DetNet Service Sub-layer
   7.  IANA Considerations
   8.  Security Considerations
   9.  Privacy Considerations
   10. References
     10.1.  Normative References
     10.2.  Informative References
   Acknowledgments
   Authors' Addresses

1.  Introduction

   Deterministic Networking (DetNet) [RFC8655] has proposed to provide a
   bounded end-to-end latency on top of the network infrastructure,
   comprising both Layer 2 bridged and Layer 3 routed segments.  That
   work encompasses the data plane, OAM, time synchronization,
   management, control, and security aspects.

   Operations, Administration, and Maintenance (OAM) tools are of
   primary importance for IP networks [RFC7276].  DetNet OAM should
   provide a toolset for fault detection, localization, and performance
   measurement.

   This document's primary purpose is to detail the specific
   requirements of the OAM features recommended to maintain a
   deterministic/reliable network.  Specifically, it investigates the
   requirements for a deterministic network that supports critical
   flows.

   In this document, the term "OAM" will be used according to its
   definition specified in [RFC6291].  DetNet is expected to implement
   an OAM framework to maintain a real-time view of the network
   infrastructure, and its ability to respect the Service Level
   Objectives (SLOs), such as in-order packet delivery, packet delay,
   delay variation, and packet-loss ratio, assigned to each DetNet flow.

   This document lists the OAM functional requirements for a DetNet
   domain.  The list can further be used for gap analysis of available
   OAM tools to identify:

   *  possible enhancements of existing tools, or

   *  whether new OAM tools are required to support proactive and on-
      demand path monitoring and service validation.

1.1.  Definitions

   This document uses definitions, particularly of a DetNet flow,
   provided in Section 2.1 of [RFC8655].  The following terms are used
   throughout this document as defined below:

   DetNet OAM domain:  a DetNet network used by the monitored DetNet
      flow.  A DetNet OAM domain (also referred to in this document as
      "OAM domain") may have Maintenance End Points (MEPs) on its edge
      and Maintenance Intermediate Points (MIPs) within.

   DetNet OAM instance:  a function that monitors a DetNet flow for
      defects and/or measures its performance metrics.  Within this
      document, the shorter version "OAM instance" is used
      interchangeably.

   Maintenance End Point (MEP):  an OAM instance that is capable of
      generating OAM test packets in the particular sub-layer of the
      DetNet OAM domain.

   Maintenance Intermediate Point (MIP):  an OAM instance along the
      DetNet flow in the particular sub-layer of the DetNet OAM domain.
      An active MIP MUST respond to an OAM message generated by the MEP
      at its sub-layer of the same DetNet OAM domain.

   Control and management plane:  the control and management planes are
      used to configure and control the network.  Relative to a DetNet
      flow, the control and/or management plane can be out of band.

   Active measurement methods:  (as defined in [RFC7799]) these methods
      modify a DetNet flow by injecting specially constructed test
      packets [RFC2544].

   Passive measurement methods:  (as defined in [RFC7799]) these methods
      infer information by observing unmodified existing flows.

   Hybrid measurement methods:  (as defined in [RFC7799]) the
      combination of elements of both active and passive measurement
      methods.

   In-band OAM:  an active OAM method that is in band within the
      monitored DetNet OAM domain when it traverses the same set of
      links and interfaces receiving the same QoS and Packet
      Replication, Elimination, and Ordering Functions (PREOF) treatment
      as the monitored DetNet flow.

   Out-of-band OAM:  an active OAM method whose path through the DetNet
      domain may not be topologically identical to the path of the
      monitored DetNet flow, its test packets may receive different QoS
      and/or PREOF treatment, or both.

   On-path telemetry:  on-path telemetry can be realized as a hybrid OAM
      method.  The origination of the telemetry information is
      inherently in band as packets in a DetNet flow are used as
      triggers.  Collection of the on-path telemetry information can be
      performed using in-band or out-of-band OAM methods.

1.2.  Requirements Language

   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 requirements language is used in
   Sections 1.1 and 6, and applies to the implementations of DetNet OAM.

2.  Role of OAM in DetNet

   DetNet networks are expected to provide communications with
   predictable low packet delay, packet loss, and packet misordering.
   Most critical applications will define a set of SLOs to be required
   for the DetNet flows they generate.

   To respect strict guarantees, DetNet can use an orchestrator able to
   monitor and maintain the network.  Typically, a Software-Defined
   Network (SDN) controller places DetNet flows in the deployed network
   based on their SLOs.  Thus, resources have to be provisioned a priori
   for the regular operation of the network.

   Most of the existing OAM tools can be used in DetNet networks, but
   they can only cover some aspects of deterministic networking.
   Fulfilling strict guarantees is essential for DetNet flows, resulting
   in new DetNet-specific functionalities that must be covered with OAM.
   Filling these gaps is inevitable and needs accurate consideration of
   DetNet specifics.  Similar to DetNet flows, their OAM also needs
   careful end-to-end engineering.

   For example, appropriate placing of MEPs along the path of a DetNet
   flow is not always a trivial task and may require proper design
   together with the design of the service component of a given DetNet
   flow.

   There are several DetNet-specific challenges for OAM.  Bounded
   network characteristics (e.g., delay, loss) are inseparable service
   parameters; therefore, Performance Monitoring (PM) OAM is a key topic
   for DetNet.  OAM tools are needed to monitor each SLO without
   impacting the DetNet flow characteristics.  A further challenge is
   strict resource allocation.  Resources used by OAM must be considered
   and allocated to avoid disturbing DetNet flows.

   The DetNet Working Group has defined two sub-layers:

      The DetNet service sub-layer at which a DetNet service (e.g.,
      service protection) is provided.

      The DetNet forwarding sub-layer, which optionally provides
      resource allocation for DetNet flows over paths provided by the
      underlying network.

   OAM mechanisms exist for the DetNet forwarding sub-layer, but the
   service sub-layer requires new OAM procedures.  These new OAM
   functions must allow, for example, recognizing/discovering DetNet
   relay nodes, getting information about their configuration, and
   checking their operation or status.

   DetNet service sub-layer functions use a sequence number for PREOF,
   which creates a challenge for inserting OAM packets in the DetNet
   flow.

   Fault tolerance also assumes that multiple paths could be provisioned
   to maintain an end-to-end circuit by adapting to the existing
   conditions.  The DetNet Controller Plane, e.g., central controller/
   orchestrator, controls the PREOF on a node.  OAM is expected to
   support monitoring and troubleshooting PREOF on a particular node and
   within the domain.

   Note that a distributed architecture of the DetNet Control Plane can
   also control PREOF in those scenarios where DetNet solutions involve
   more than one single central controller.

   The DetNet forwarding sub-layer is based on preexisting technologies
   and has much better coverage regarding OAM.  However, the forwarding
   sub-layer is terminated at DetNet relay nodes, so the end-to-end OAM
   state of forwarding may be created only based on the status of
   multiple forwarding sub-layer segments serving a given DetNet flow
   (e.g., in case of DetNet MPLS, there may be no end-to-end LSP below
   the DetNet pseudowire).

3.  Operation

   OAM features will enable DetNet with robust operation both for
   forwarding and routing purposes.

   It is worth noting that the test and data packets are expected to
   follow the same path, i.e., connectivity verification has to be
   conducted in band without impacting data traffic.  It is expected
   that test packets share fate with the monitored data traffic without
   introducing congestion in normal network conditions.

3.1.  Information Collection

   Information about the state of the network can be collected using
   several mechanisms.  Some protocols, e.g., the Simple Network
   Management Protocol (SNMP), poll for updated data.  Other protocols,
   such as YANG-Push [RFC8641], can be used to set up subscriptions for
   the data defined in the YANG data models to be published periodically
   or when the underlying data changes.  Either way, information is
   collected and sent using the DetNet Controller Plane.

   Also, we can characterize methods of transporting OAM information
   relative to the path of data.  For instance, OAM information may be
   transported in band or out of band relative to the DetNet flow.  In
   the case of the former, the telemetry information uses resources
   allocated for the monitored DetNet flow.  If an in-band method of
   transporting telemetry is used, the amount of generated information
   needs to be carefully analyzed, and additional resources must be
   reserved.  [RFC9197] defines the in-band transport mechanism where
   telemetry information is collected in the data packet on which
   information is generated.  Two tracing methods are described:

   *  end-to-end, i.e., from the ingress and egress nodes, and

   *  hop-by-hop, i.e., like end-to-end with additional information from
      transit nodes.

   [RFC9326] and [HYBRID-TWO-STEP] are examples of out-of-band telemetry
   transport.  In the former case, information is transported by each
   node traversed by the data packet of the monitored DetNet flow in a
   specially constructed packet.  In the latter, information is
   collected in a sequence of follow-up packets that traverse the same
   path as the data packet of the monitored DetNet flow.  In both
   methods, transport of the telemetry can avoid using resources
   allocated for the DetNet domain.

3.2.  Continuity Check

   A continuity check is used to monitor the continuity of a path, i.e.,
   that there exists a way to deliver packets between MEP A and MEP B.
   The continuity check detects a network failure in one direction: from
   the MEP transmitting test packets to the remote egress MEP.  The
   continuity check in a DetNet OAM domain monitors the DetNet
   forwarding sub-layer; thus, it is not affected by a PREOF that
   operates at the DetNet service sub-layer ([RFC8655]).

3.3.  Connectivity Verification

   In addition to the Continuity Check, DetNet solutions have to verify
   connectivity.  This verification considers an additional constraint:
   the absence of misconnection.  The misconnection error state is
   entered after several consecutive test packets from other DetNet
   flows are received.  The definition of the conditions for entry and
   exit of a misconnection error state is outside the scope of this
   document.  Connectivity verification in a DetNet OAM domain monitors
   the DetNet forwarding sub-layer; thus, it is not affected by PREOF
   that operates at the DetNet service sub-layer ([RFC8655]).

3.4.  Route Tracing

   Ping and traceroute are two ubiquitous tools that help localize and
   characterize a failure in the network using an echo request/reply
   mechanism.  They help to identify a subset of the routers in the
   path.  However, to be predictable, resources are reserved per flow in
   DetNet.  Thus, DetNet needs to define route tracing tools able to
   trace the route for a specific flow.  Also, tracing can be used for
   the discovery of the Path Maximum Transmission Unit (PMTU) or
   location of elements of PREOF for the particular route in the DetNet
   domain.

   DetNet is not expected to use Equal-Cost Multipath (ECMP) [RFC8939].
   As a result, DetNet OAM in an ECMP environment is outside the scope
   of this document.

3.5.  Fault Verification/Detection

   DetNet expects to operate fault-tolerant networks.  Thus, mechanisms
   able to detect faults before they impact network performance are
   needed.

   The network has to detect when a fault has occurred, i.e., the
   network has deviated from its expected behavior.  Fault detection can
   be based on proactive OAM protocols like continuity check or on-
   demand methods like ping.  While the network must report an alarm,
   the cause may not be identified precisely.  Examples of such alarms
   are significant degradation of the end-to-end reliability or when a
   buffer overflow occurs.

3.6.  Fault Localization and Characterization

   The ability to localize a network defect and provide its
   characterization are necessary elements of network operation.

   Fault localization:  a process of deducing the location of a network
      failure from a set of observed failure indications.  For example,
      this might be achieved by tracing the route of the DetNet flow in
      which the network failure was detected.  Another method of fault
      localization can correlate reports of failures from a set of
      interleaved sessions monitoring path continuity.

   Fault characterization:  a process of identifying the root cause of
      the problem.  For instance, misconfiguration or malfunction of
      PREOF elements can be the cause of erroneous packet replication or
      extra packets being flooded in the DetNet domain.

3.7.  Use of Hybrid OAM in DetNet

   Hybrid OAM methods are used in performance monitoring and defined in
   [RFC7799] as follows:

   |  Hybrid Methods are Methods of Measurement that use a combination
   |  of Active Methods and Passive Methods.

   A hybrid measurement method can produce metrics as close to measured
   using a passive measurement method.  The passive methods measure
   metrics closest to the network's actual conditions.  A hybrid method,
   even if it alters something in a data packet, even if that is as
   little as the value of a designated field in the packet
   encapsulation, is considered an approximation of a passive
   measurement method.  One example of such a hybrid measurement method
   is the Alternate-Marking Method (AMM) described in [RFC9341].  As
   with all on-path telemetry methods, AMM in a DetNet domain with the
   IP data plane is, by design, in band with respect to the monitored
   DetNet flow.  Because the marking is applied to a data flow, measured
   metrics are directly applicable to the DetNet flow.  AMM minimizes
   the additional load on the DetNet domain by using nodal collection
   and computation of performance metrics optionally in combination with
   using out-of-band telemetry collection for further network analysis.

4.  Administration

   The ability to expose a collection of metrics to support an
   operator's decision-making is essential.  The following performance
   metrics are useful:

   Queuing Delay:  the time elapsed between enqueuing a packet and its
      transmission to the next hop.

   Buffer occupancy:  the number of packets present in the buffer for
      each of the existing flows.

   Per DetNet flow:  a metric reflecting end-to-end performance for a
      given flow.  Each of the paths has to be isolated in a multipath
      routing environment.

   Per-path:  detection of a misbehaving path or paths when multiple
      paths are used for the service protection.

   Per-device:  detection of a misbehaving device.

4.1.  Collection of Metrics

   It is important to optimize the volume and frequency of statistics/
   measurement collection, whether the mechanisms are distributed,
   centralized, or both.  Periodic and event-triggered collection
   information characterizing the state of a network is an example of
   mechanisms to achieve the optimization.

4.2.  Worst-Case Metrics

   DetNet aims to enable real-time communications on top of a
   heterogeneous multi-hop architecture.  To make correct decisions, the
   DetNet Controller Plane [RFC8655] needs timely information about
   packet losses/delays for each flow and each hop of the paths.  In
   other words, just the average end-to-end statistics are not enough.
   The collected information must be sufficient to allow a system to
   predict the worst-case scenario.

5.  Maintenance

   Service protection (provided by the DetNet Service sub-layer) is
   designed to mitigate simple network failures more rapidly than the
   expected response time of the DetNet Controller Plane.  In the face
   of events that impact network operation (e.g., link up/down, device
   crash/reboot, flows starting and ending), the DetNet Controller Plane
   needs to perform repair and reoptimization actions in order to
   permanently ensure SLOs of all active flows with minimal waste of
   resources.  The Controller Plane is expected to be able to
   continuously retrieve the state of the network, to evaluate
   conditions and trends about the relevance of a reconfiguration,
   quantifying the following:

   the cost of the suboptimality:  resources may not be used optimally
      (i.e., a better path exists).

   the reconfiguration cost:  the DetNet Controller Plane needs an
      ability to trigger some reconfigurations.  For this transient
      period, resources may be twice reserved, and control packets have
      to be transmitted.

   Thus, reconfiguration may only be triggered if the gain is
   significant.

5.1.  Replication/Elimination

   When multiple paths are reserved between two MEPs, packet replication
   may be used to introduce redundancy and alleviate transmission errors
   and collisions.  For instance, in Figure 1, the source device S
   transmits a packet to devices A and B to reach the destination node
   R.


                          ===> (A) => (C) => (E) ===
                        //        \\//   \\//       \\
              source (S)          //\\   //\\         (R) (root)
                        \\       //  \\ //  \\      //
                          ===> (B) => (D) => (F) ===

           Figure 1: Packet Replication and Elimination Functions

5.2.  Resource Reservation

   Because the quality of service associated with a path may degrade,
   the network has to provision additional resources along the path.

6.  Requirements

   According to [RFC8655], DetNet functionality is divided into
   forwarding and service sub-layers.  The DetNet forwarding sub-layer
   includes DetNet transit nodes and may allocate resources for a DetNet
   flow over paths provided by the underlay network.  The DetNet service
   sub-layer includes DetNet relay nodes and provides a DetNet service
   (e.g., service protection).  This section lists general requirements
   for DetNet OAM as well as requirements in each of the DetNet sub-
   layers of a DetNet domain.

   1.  It MUST be possible to initiate a DetNet OAM session from a MEP
       located at a DetNet node towards a MEP or MEPs downstream from
       that DetNet node within the given domain at a particular DetNet
       sub-layer.

   2.  It MUST be possible to initiate a DetNet OAM session using any of
       the DetNet Controller Plane solutions, e.g., a centralized
       controller.

   3.  DetNet OAM MUST support proactive OAM monitoring and measurement
       methods.

   4.  DetNet OAM MUST support on-demand OAM monitoring and measurement
       methods.

   5.  DetNet OAM MUST support unidirectional OAM methods, continuity
       checks, connectivity verification, and performance measurements.

   6.  DetNet OAM MUST support bidirectional DetNet flows, but it is not
       required to support bidirectional OAM methods for bidirectional
       DetNet flows.  DetNet OAM test packets used for monitoring and
       measurements of a bidirectional DetNet flow MUST be in band in
       both directions.

   7.  DetNet OAM MUST support proactive monitoring of a DetNet device's
       reachability for a given DetNet flow.

   8.  DetNet OAM MUST support hybrid performance measurement methods.

   9.  Calculated performance metrics MUST include, but are not limited
       to, throughput, packet-loss, out-of-order, delay, and delay-
       variation metrics.  [RFC6374] provides detailed information on
       performance measurement and performance metrics.

6.1.  For the DetNet Forwarding Sub-layer

   DetNet OAM MUST support:

   1.  PMTU discovery.

   2.  Remote Defect Indication (RDI) notification to the DetNet OAM
       instance performing continuity checking.

   3.  the monitoring of levels of resources allocated for a particular
       DetNet flow.  Such resources include, but are not limited to,
       buffer utilization and scheduler transmission calendar.

   4.  the monitoring of any subset of paths traversed through the
       DetNet domain by a DetNet flow.

6.2.  For the DetNet Service Sub-layer

   The OAM functions for the DetNet service sub-layer allow, for
   example, the recognizing/discovery of DetNet relay nodes, the
   gathering of information about their configuration, and the checking
   of their operation or status.

   The requirements on OAM for a DetNet relay node are that DetNet OAM
   MUST:

   1.  provide OAM functions for the DetNet service sub-layer.

   2.  support the discovery of DetNet relay nodes in a DetNet network.

   3.  support the discovery of PREOF locations in the domain.

   4.  support the collection of information specific to the DetNet
       service sub-layer (configuration/operation/status) from DetNet
       relay nodes.

   5.  support exercising functionality of PREOF in the domain.

   6.  work for DetNet data planes: MPLS and IP.

   7.  support a defect notification mechanism, like Alarm Indication
       Signal.  Any DetNet relay node providing service for a given
       DetNet flow MAY originate a defect notification addressed to any
       subset of DetNet relay nodes along that flow.

   8.  be able to measure metrics (e.g. delay) inside a collection of
       OAM sessions, specially for complex DetNet flows, with PREOF
       features.

7.  IANA Considerations

   This document has no IANA actions.

8.  Security Considerations

   This document lists the OAM requirements for a DetNet domain and does
   not raise any security concerns or issues in addition to ones common
   to networking and those specific to DetNet that are discussed in
   Section 9 of [RFC9055].  Furthermore, the analysis of OAM security
   concerns in Section 6 of [RFC7276] also applies to DetNet OAM,
   including the use of OAM for network reconnaissance.

9.  Privacy Considerations

   Privacy considerations of DetNet discussed in Section 13 of [RFC9055]
   are also applicable to DetNet OAM.  If any privacy mechanism is used
   for the monitored DetNet flow, then the same privacy method MUST be
   applied to the active DetNet OAM used to monitor the flow.

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

   [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>.

   [RFC8655]  Finn, N., Thubert, P., Varga, B., and J. Farkas,
              "Deterministic Networking Architecture", RFC 8655,
              DOI 10.17487/RFC8655, October 2019,
              <https://www.rfc-editor.org/info/rfc8655>.

10.2.  Informative References

   [HYBRID-TWO-STEP]
              Mirsky, G., Lingqiang, W., Zhui, G., Song, H., and P.
              Thubert, "Hybrid Two-Step Performance Measurement Method",
              Work in Progress, Internet-Draft, draft-ietf-ippm-hybrid-
              two-step-00, 4 October 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-ippm-
              hybrid-two-step-00>.

   [RFC2544]  Bradner, S. and J. McQuaid, "Benchmarking Methodology for
              Network Interconnect Devices", RFC 2544,
              DOI 10.17487/RFC2544, March 1999,
              <https://www.rfc-editor.org/info/rfc2544>.

   [RFC6291]  Andersson, L., van Helvoort, H., Bonica, R., Romascanu,
              D., and S. Mansfield, "Guidelines for the Use of the "OAM"
              Acronym in the IETF", BCP 161, RFC 6291,
              DOI 10.17487/RFC6291, June 2011,
              <https://www.rfc-editor.org/info/rfc6291>.

   [RFC6374]  Frost, D. and S. Bryant, "Packet Loss and Delay
              Measurement for MPLS Networks", RFC 6374,
              DOI 10.17487/RFC6374, September 2011,
              <https://www.rfc-editor.org/info/rfc6374>.

   [RFC7276]  Mizrahi, T., Sprecher, N., Bellagamba, E., and Y.
              Weingarten, "An Overview of Operations, Administration,
              and Maintenance (OAM) Tools", RFC 7276,
              DOI 10.17487/RFC7276, June 2014,
              <https://www.rfc-editor.org/info/rfc7276>.

   [RFC7799]  Morton, A., "Active and Passive Metrics and Methods (with
              Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
              May 2016, <https://www.rfc-editor.org/info/rfc7799>.

   [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>.

   [RFC8939]  Varga, B., Ed., Farkas, J., Berger, L., Fedyk, D., and S.
              Bryant, "Deterministic Networking (DetNet) Data Plane:
              IP", RFC 8939, DOI 10.17487/RFC8939, November 2020,
              <https://www.rfc-editor.org/info/rfc8939>.

   [RFC9055]  Grossman, E., Ed., Mizrahi, T., and A. Hacker,
              "Deterministic Networking (DetNet) Security
              Considerations", RFC 9055, DOI 10.17487/RFC9055, June
              2021, <https://www.rfc-editor.org/info/rfc9055>.

   [RFC9197]  Brockners, F., Ed., Bhandari, S., Ed., and T. Mizrahi,
              Ed., "Data Fields for In Situ Operations, Administration,
              and Maintenance (IOAM)", RFC 9197, DOI 10.17487/RFC9197,
              May 2022, <https://www.rfc-editor.org/info/rfc9197>.

   [RFC9326]  Song, H., Gafni, B., Brockners, F., Bhandari, S., and T.
              Mizrahi, "In Situ Operations, Administration, and
              Maintenance (IOAM) Direct Exporting", RFC 9326,
              DOI 10.17487/RFC9326, November 2022,
              <https://www.rfc-editor.org/info/rfc9326>.

   [RFC9341]  Fioccola, G., Ed., Cociglio, M., Mirsky, G., Mizrahi, T.,
              and T. Zhou, "Alternate-Marking Method", RFC 9341,
              DOI 10.17487/RFC9341, December 2022,
              <https://www.rfc-editor.org/info/rfc9341>.

Acknowledgments

   The authors express their appreciation and gratitude to Pascal
   Thubert for the review, insightful questions, and helpful comments.

Authors' Addresses

   Greg Mirsky
   Ericsson
   Email: gregimirsky@gmail.com


   Fabrice Theoleyre
   CNRS
   ICube Lab, Pole API
   300 boulevard Sebastien Brant - CS 10413
   67400 Illkirch - Strasbourg
   France
   Phone: +33 368 85 45 33
   Email: fabrice.theoleyre@cnrs.fr
   URI:   https://fabrice.theoleyre.cnrs.fr/


   Georgios Papadopoulos
   IMT Atlantique
   Office B00 - 102A
   2 Rue de la Châtaigneraie
   35510 Cesson-Sévigné - Rennes
   France
   Phone: +33 299 12 70 04
   Email: georgios.papadopoulos@imt-atlantique.fr


   Carlos J. Bernardos
   Universidad Carlos III de Madrid
   Av. Universidad, 30
   28911 Leganes, Madrid
   Spain
   Phone: +34 91624 6236
   Email: cjbc@it.uc3m.es
   URI:   http://www.it.uc3m.es/cjbc/


   Balazs Varga
   Ericsson
   Budapest
   Magyar Tudosok krt. 11.
   1117
   Hungary
   Email: balazs.a.varga@ericsson.com


   Janos Farkas
   Ericsson
   Budapest
   Magyar Tudosok krt. 11.
   1117
   Hungary
   Email: janos.farkas@ericsson.com
