Internet Engineering Task Force (IETF)                         G. Mirsky
Request for Comments: 9546                                      Ericsson
Category: Standards Track                                        M. Chen
ISSN: 2070-1721                                                   Huawei
                                                               B. Varga
                                                               Ericsson
                                                          February 2024


 Operations, Administration, and Maintenance (OAM) for Deterministic
             Networking (DetNet) with the MPLS Data Plane

Abstract

  This document defines format and usage principles of the
  Deterministic Networking (DetNet) service Associated Channel over a
  DetNet network with the MPLS data plane.  The DetNet service
  Associated Channel can be used to carry test packets of active
  Operations, Administration, and Maintenance (OAM) protocols that are
  used to detect DetNet failures and measure performance metrics.

Status of This Memo

  This is an Internet Standards Track document.

  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).  Further information on
  Internet Standards is available in 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/rfc9546.

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
  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 Revised BSD License text as described in Section 4.e of the
  Trust Legal Provisions and are provided without warranty as described
  in the Revised BSD License.

Table of Contents

  1.  Introduction
  2.  Conventions Used in This Document
    2.1.  Terminology and Acronyms
    2.2.  Key Words
  3.  Active OAM for DetNet Networks with the MPLS Data Plane
    3.1.  DetNet Active OAM Encapsulation
    3.2.  DetNet PREOF Interaction with Active OAM
  4.  OAM Interworking Models
    4.1.  OAM of DetNet MPLS Interworking with OAM of TSN
    4.2.  OAM of DetNet MPLS Interworking with OAM of DetNet IP
  5.  IANA Considerations
    5.1.  DetNet Associated Channel Header (d-ACH) Flags Registry
  6.  Security Considerations
  7.  References
    7.1.  Normative References
    7.2.  Informative References
  Acknowledgments
  Authors' Addresses

1.  Introduction

  [RFC8655] introduces and explains Deterministic Networking (DetNet)
  architecture and how the Packet Replication, Elimination, and
  Ordering Functions (PREOF) can be used to ensure a low packet drop
  ratio in a DetNet domain.

  Operations, Administration, and Maintenance (OAM) protocols are used
  to detect and localize network defects and to monitor network
  performance.  Some OAM functions (e.g., failure detection) are
  usually performed proactively in the network, while others (e.g.,
  defect localization) are typically performed on demand.  These tasks
  can be achieved through a combination of active and hybrid OAM
  methods, as classified in [RFC7799].  This document presents a format
  for active OAM in DetNet networks with the MPLS data plane.

  Also, this document defines format and usage principles of the DetNet
  service Associated Channel over a DetNet network with the MPLS data
  plane [RFC8964].

2.  Conventions Used in This Document

2.1.  Terminology and Acronyms

  The term "DetNet OAM" in this document is used interchangeably with a
  "set of OAM protocols, methods, and tools for Deterministic
  Networking".

  BFD:  Bidirectional Forwarding Detection

  CFM:  Connectivity Fault Management

  d-ACH:  DetNet Associated Channel Header

  DetNet:  Deterministic Networking

  DetNet Node:  A node that is an actor in the DetNet domain.  Examples
     of DetNet nodes include DetNet domain edge nodes and DetNet nodes
     that perform PREOF within the DetNet domain.

  E2E:  End to end

  F-Label:  A DetNet "forwarding" label.  The F-Label identifies the
     Label Switched Path (LSP) used to forward a DetNet flow across an
     MPLS Packet Switched Network (PSN), e.g., a hop-by-hop label used
     between label switching routers.

  OAM:  Operations, Administration, and Maintenance

  PREOF:  Packet Replication, Elimination, and Ordering Functions

  PW:  Pseudowire

  S-Label:  A DetNet "service" label.  An S-Label is used between
     DetNet nodes that implement the DetNet service sub-layer
     functions.  An S-Label is also used to identify a DetNet flow at
     the DetNet service sub-layer.

  TSN:  Time-Sensitive Networking

  Underlay Network or Underlay Layer:  The network that provides
     connectivity between the DetNet nodes.  One example of an underlay
     layer is an MPLS network that provides LSP connectivity between
     DetNet nodes.

2.2.  Key Words

  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.

3.  Active OAM for DetNet Networks with the MPLS Data Plane

  OAM protocols and mechanisms act within the data plane of the
  particular networking layer; thus, it is critical that the data plane
  encapsulation supports OAM mechanisms that comply with the OAM
  requirements listed in [OAM-FRAMEWORK].

  Operation of a DetNet data plane with an MPLS underlay network is
  specified in [RFC8964].  Within the MPLS underlay network, DetNet
  flows are to be encapsulated analogous to pseudowires (PWs) as
  specified in [RFC3985] and [RFC4385].  For reference, the Generic PW
  MPLS Control Word (as defined in [RFC4385] and used with DetNet) is
  reproduced in Figure 1.


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0 0 0 0|                Sequence Number                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 1: Generic PW MPLS Control Word Format

  PREOF in the DetNet domain is composed of a combination of nodes that
  perform replication and elimination functions.  The Elimination sub-
  function always uses the S-Label in conjunction with the packet
  sequencing information (i.e., the Sequence Number encoded in the
  DetNet Control Word).  The Replication sub-function uses the S-Label
  information only.

3.1.  DetNet Active OAM Encapsulation

  DetNet OAM, like PW OAM, uses the PW Associated Channel Header
  defined in [RFC4385].  At the same time, a DetNet PW can be viewed as
  a Multi-Segment PW, where DetNet service sub-layer functions are at
  the segment endpoints.  However, DetNet service sub-layer functions
  operate per packet level (not per segment).  These per-packet level
  characteristics of PREOF require additional fields for proper OAM
  packet processing.  MPLS encapsulation [RFC8964] of a DetNet active
  OAM packet is shown in Figure 2.


        +---------------------------------+
        |                                 |
        |        DetNet OAM Packet        |
        |                                 |
        +---------------------------------+ <--\
        | DetNet Associated Channel Header|    |
        +---------------------------------+    +--> DetNet active OAM
        |           S-Label               |    |    MPLS encapsulation
        +---------------------------------+    |
        |         [ F-Label(s) ]          |    |
        +---------------------------------+ <--/
        |           Data-Link             |
        +---------------------------------+
        |           Physical              |
        +---------------------------------+

    Figure 2: DetNet Active OAM Packet Encapsulation in the MPLS Data
                                  Plane

  Figure 3 displays encapsulation of a test packet for a DetNet active
  OAM protocol in case of MPLS over UDP/IP [RFC9025].


        +---------------------------------+
        |                                 |
        |        DetNet OAM Packet        |
        |                                 |
        +---------------------------------+ <--\
        | DetNet Associated Channel Header|    |
        +---------------------------------+    +--> DetNet active OAM
        |             S-Label             |    |    MPLS encapsulation
        +---------------------------------+    |
        |          [ F-label(s) ]         |    |
        +---------------------------------+ <--+
        |           UDP Header            |    |
        +---------------------------------+    +--> DetNet data plane
        |           IP Header             |    |    IP encapsulation
        +---------------------------------+ <--/
        |           Data-Link             |
        +---------------------------------+
        |           Physical              |
        +---------------------------------+

   Figure 3: DetNet Active OAM Packet Encapsulation in MPLS over UDP/IP

  Figure 4 displays the format of the DetNet Associated Channel Header
  (d-ACH).


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 1|Version|Sequence Number|         Channel Type          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                 Node ID               |Level|  Flags  |Session|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                          Figure 4: d-ACH Format

  The d-ACH encodes the following fields:
     Bits 0..3:  These MUST be 0b0001.  This allows the packet to be
        distinguished from an IP packet [RFC4928] and from a DetNet
        data packet [RFC8964].

     Version:  A 4-bit field.  This document specifies version 0.

     Sequence Number:  An unsigned circular 8-bit field.  Because a
        DetNet active OAM test packet includes d-ACH, Section 4.2.1 of
        [RFC8964] does not apply to handling the Sequence Number field
        in DetNet OAM over the MPLS data plane.  The sequence number
        space is circular with no restriction on the initial value.
        The originator DetNet node MUST set the value of the Sequence
        Number field before the transmission of a packet.  The initial
        value SHOULD be random (unpredictable).  The originator node
        SHOULD increase the value of the Sequence Number field by 1 for
        each active OAM packet.  The originator MAY use other
        strategies, e.g., for negative testing of Packet Ordering
        Functions.

     Channel Type:  A 16-bit field and the value of the DetNet
        Associated Channel Type.  It MUST be one of the values listed
        in the IANA "MPLS Generalized Associated Channel (G-ACh) Types
        (including Pseudowire Associated Channel Types)" registry
        [IANA-G-ACh-Types].

     Node ID:  An unsigned 20-bit field.  The value of the Node ID
        field identifies the DetNet node that originated the packet.  A
        DetNet node MUST be provisioned with a Node ID that is unique
        in the DetNet domain.  Methods for distributing Node ID are
        outside the scope of this specification.

     Level:  A 3-bit field.  Semantically, the Level field is analogous
        to the Maintenance Domain Level in [IEEE.802.1Q].  The Level
        field is used to cope with the "all active path forwarding"
        (defined by the TSN Task Group of the IEEE 802.1 WG
        [IEEE802.1TSNTG]) characteristics of the PREOF concept.  A
        hierarchical relationship between OAM domains can be created
        using the Level field value, as illustrated by Figure 18.7 in
        [IEEE.802.1Q].

     Flags:  A 5-bit field.  The Flags field contains five 1-bit flags.
        Section 5.1 creates the IANA "DetNet Associated Channel Header
        (d-ACH) Flags" registry for new flags to be defined.  The flags
        defined in this specification are presented in Figure 5.

     Session ID:  A 4-bit field.  The Session field distinguishes OAM
        sessions originating from the same node (a given Maintenance
        End Point may have multiple simultaneously active OAM sessions)
        at the given Level.


         0 1 2 3 4
        +-+-+-+-+-+
        |U|U|U|U|U|
        +-+-+-+-+-+

         Figure 5: DetNet Associated Channel Header Flags Field Format

  U:  Unused and for future use.  MUST be 0 on transmission and ignored
     on receipt.

  According to [RFC8964], a DetNet flow is identified by the S-Label
  that MUST be at the bottom of the stack.  An active OAM packet MUST
  include d-ACH immediately following the S-Label.

3.2.  DetNet PREOF Interaction with Active OAM

  At the DetNet service sub-layer, special functions (notably PREOF)
  MAY be applied to the particular DetNet flow to potentially reduce
  packet loss, improve the probability of on-time packet delivery, and
  ensure in-order packet delivery.  PREOF relies on sequencing
  information in the DetNet service sub-layer.  For a DetNet active OAM
  packet, PREOF MUST use the Sequence Number field value as the source
  of this sequencing information.  App-flow and OAM use different
  sequence number spaces.  PREOF algorithms are executed with respect
  to the sequence number space identified by the flow's characteristic
  information.  Although the Sequence Number field in d-ACH has a range
  from 0 through 255, it provides sufficient space because the rate of
  DetNet active OAM packets is significantly lower compared to the rate
  of DetNet packets in an App-flow; therefore, wrapping around is not
  an issue.

4.  OAM Interworking Models

  Interworking of two OAM domains that utilize different networking
  technology can be realized by either a peering model or a tunneling
  model.  In a peering model, OAM domains are within the corresponding
  network domain.  When using the peering model, state changes that are
  detected by a Fault Management OAM protocol can be mapped from one
  OAM domain into another or a notification, e.g., an alarm can be sent
  to a central controller.  In the tunneling model of OAM interworking,
  usually only one active OAM protocol is used.  Its test packets are
  tunneled through another domain along with the data flow, thus
  ensuring fate sharing among test and data packets.

4.1.  OAM of DetNet MPLS Interworking with OAM of TSN

  DetNet active OAM can provide end-to-end (E2E) fault management and
  performance monitoring for a DetNet flow.  In the case of DetNet with
  an MPLS data plane and an IEEE 802.1 Time-Sensitive Networking (TSN)
  sub-network, it implies the interworking of DetNet active OAM with
  TSN OAM, of which the data plane aspects are specified in [RFC9037].

  When the peering model (Section 4) is used in the Connectivity Fault
  Management (CFM) OAM protocol [IEEE.802.1Q], the node that borders
  both TSN and DetNet MPLS domains MUST support [RFC7023].  [RFC7023]
  specifies the mapping of defect states between Ethernet Attachment
  Circuits and associated Ethernet PWs that are part of an E2E emulated
  Ethernet service and are also applicable to E2E OAM across DetNet
  MPLS and TSN domains.  The CFM [IEEE.802.1Q] [ITU.Y1731] can provide
  fast detection of a failure in the TSN segment of the DetNet service.
  In the DetNet MPLS domain, Bidirectional Forwarding Detection (BFD),
  as specified in [RFC5880] and [RFC5885], can be used.  To provide E2E
  failure detection, the TSN and DetNet MPLS segments could be treated
  as concatenated such that the diagnostic codes (see Section 6.8.17 of
  [RFC5880]) MAY be used to inform the upstream DetNet MPLS node of a
  TSN segment failure.  Performance monitoring can be supported by
  [RFC6374] in the DetNet MPLS and by [ITU.Y1731] in TSN domains,
  respectively.  Performance objectives for each domain should refer to
  metrics that are composable [RFC6049] or are defined for each domain
  separately.

  The following considerations apply when using the tunneling model of
  OAM interworking between DetNet MPLS and TSN domains based on general
  principles described in Section 4 of [RFC9037]:

  *  Active OAM test packets MUST be mapped to the same TSN Stream ID
     as the monitored DetNet flow.

  *  Active OAM test packets MUST be processed in the TSN domain based
     on their S-Label and Class of Service marking (the Traffic Class
     field value).

  Mapping between a DetNet flow and TSN Stream in the TSN sub-network
  is described in Section 4.1 of [RFC9037].  The mapping has to be done
  only on the edge node of the TSN sub-network, and intermediate TSN
  nodes do not need to recognize the S-Label.  An edge node has two
  components:

  1.  A passive Stream identification function.

  2.  An active Stream identification function.

  The first component identifies the DetNet flow (using Clause 6.8 of
  [IEEE.802.1CBdb]), and the second component creates the TSN Stream by
  manipulating the Ethernet header.  That manipulation simplifies the
  identification of the TSN Stream in the intermediate TSN nodes by
  avoiding the need for them to look outside of the Ethernet header.
  DetNet MPLS OAM packets use the same S-Label as the DetNet flow data
  packets.  The above-described mapping function treats these OAM
  packets as data packets of the DetNet flow.  As a result, DetNet MPLS
  OAM packets are fate sharing within the TSN sub-network.  As an
  example of the mapping between DetNet MPLS and TSN, see Annex C.1 of
  [IEEE.802.1CBdb] that, in support of [RFC9037], describes how to
  match MPLS DetNet flows and achieve TSN Streams.

  Note that the tunneling model of the OAM interworking requires that
  the remote peer of the E2E OAM domain supports the active OAM
  protocol selected on the ingress endpoint.  For example, if BFD is
  used for proactive path continuity monitoring in the DetNet MPLS
  domain, BFD support (as defined in [RFC5885]) is necessary at any TSN
  endpoint of the DetNet service.

4.2.  OAM of DetNet MPLS Interworking with OAM of DetNet IP

  Interworking between active OAM segments in DetNet MPLS and DetNet IP
  domains can also be realized using either the peering model or the
  tunneling model, as discussed in Section 4.1.  Using the same
  protocol, e.g., BFD over both segments, simplifies the mapping of
  errors in the peering model.  For example, respective BFD sessions in
  DetNet MPLS and DetNet IP domains can be in a concatenated
  relationship as described in Section 6.8.17 of [RFC5880].  To provide
  performance monitoring over a DetNet IP domain, the Simple Two-way
  Active Measurement Protocol (STAMP) [RFC8762] and its extensions
  [RFC8972] can be used to measure packet loss and packet delay
  metrics.  Such performance metrics can be used to calculate
  composable metrics [RFC6049] within DetNet MPLS and DetNet IP domains
  to reflect the end-to-end DetNet service performance.

5.  IANA Considerations

5.1.  DetNet Associated Channel Header (d-ACH) Flags Registry

  IANA has created the "DetNet Associated Channel Header (d-ACH) Flags"
  registry within the "DetNet Associated Channel Header (d-ACH) Flags"
  registry group.  The registration procedure is "IETF Review"
  [RFC8126].  There are five flags in the 5-bit Flags field, as defined
  in Table 1.

                           +=====+=============+
                           | Bit | Description |
                           +=====+=============+
                           | 0-4 | Unassigned  |
                           +-----+-------------+

                              Table 1: DetNet
                             Associated Channel
                            Header (d-ACH) Flags
                                  Registry

6.  Security Considerations

  Security considerations discussed in DetNet specifications [RFC8655],
  [RFC8964], [RFC9055], and [OAM-FRAMEWORK] are applicable to this
  document.  Security concerns and issues related to MPLS OAM tools
  like LSP Ping [RFC8029] and BFD over PW [RFC5885] also apply to this
  specification.

7.  References

7.1.  Normative References

  [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119,
             DOI 10.17487/RFC2119, March 1997,
             <https://www.rfc-editor.org/info/rfc2119>.

  [RFC7023]  Mohan, D., Ed., Bitar, N., Ed., Sajassi, A., Ed., DeLord,
             S., Niger, P., and R. Qiu, "MPLS and Ethernet Operations,
             Administration, and Maintenance (OAM) Interworking",
             RFC 7023, DOI 10.17487/RFC7023, October 2013,
             <https://www.rfc-editor.org/info/rfc7023>.

  [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>.

  [RFC8964]  Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
             S., and J. Korhonen, "Deterministic Networking (DetNet)
             Data Plane: MPLS", RFC 8964, DOI 10.17487/RFC8964, January
             2021, <https://www.rfc-editor.org/info/rfc8964>.

  [RFC9025]  Varga, B., Ed., Farkas, J., Berger, L., Malis, A., and S.
             Bryant, "Deterministic Networking (DetNet) Data Plane:
             MPLS over UDP/IP", RFC 9025, DOI 10.17487/RFC9025, April
             2021, <https://www.rfc-editor.org/info/rfc9025>.

7.2.  Informative References

  [IANA-G-ACh-Types]
             IANA, "MPLS Generalized Associated Channel (G-ACh) Types
             (including Pseudowire Associated Channel Types)",
             <https://www.iana.org/assignments/g-ach-parameters/>.

  [IEEE.802.1CBdb]
             IEEE, "IEEE Standard for Local and metropolitan area
             networks--Frame Replication and Elimination for
             Reliability--Amendment 2: Extended Stream Identification
             Functions", IEEE Std 802.1CBdb-2021, December 2021.

  [IEEE.802.1Q]
             IEEE, "IEEE Standard for Local and Metropolitan Area
             Network--Bridges and Bridged Networks", IEEE Std 802.1Q-
             2018, DOI 10.1109/IEEESTD.2018.8403927, July 2018,
             <https://doi.org/10.1109/IEEESTD.2018.8403927>.

  [IEEE802.1TSNTG]
             IEEE 802.1, "Time-Sensitive Networking (TSN) Task Group",
             TSN Standards, <https://1.ieee802.org/tsn/>.

  [ITU.Y1731]
             ITU-T, "Operation, administration and maintenance (OAM)
             functions and mechanisms for Ethernet-based networks",
             ITU-T Recommendation G.8013/Y.1731, June 2023.

  [OAM-FRAMEWORK]
             Mirsky, G., Theoleyre, F., Papadopoulos, G. Z., Bernardos,
             CJ., Varga, B., and J. Farkas, "Framework of Operations,
             Administration and Maintenance (OAM) for Deterministic
             Networking (DetNet)", Work in Progress, Internet-Draft,
             draft-ietf-detnet-oam-framework-11, 8 January 2024,
             <https://datatracker.ietf.org/doc/html/draft-ietf-detnet-
             oam-framework-11>.

  [RFC3985]  Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
             Edge-to-Edge (PWE3) Architecture", RFC 3985,
             DOI 10.17487/RFC3985, March 2005,
             <https://www.rfc-editor.org/info/rfc3985>.

  [RFC4385]  Bryant, S., Swallow, G., Martini, L., and D. McPherson,
             "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
             Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385,
             February 2006, <https://www.rfc-editor.org/info/rfc4385>.

  [RFC4928]  Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal
             Cost Multipath Treatment in MPLS Networks", BCP 128,
             RFC 4928, DOI 10.17487/RFC4928, June 2007,
             <https://www.rfc-editor.org/info/rfc4928>.

  [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
             (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
             <https://www.rfc-editor.org/info/rfc5880>.

  [RFC5885]  Nadeau, T., Ed. and C. Pignataro, Ed., "Bidirectional
             Forwarding Detection (BFD) for the Pseudowire Virtual
             Circuit Connectivity Verification (VCCV)", RFC 5885,
             DOI 10.17487/RFC5885, June 2010,
             <https://www.rfc-editor.org/info/rfc5885>.

  [RFC6049]  Morton, A. and E. Stephan, "Spatial Composition of
             Metrics", RFC 6049, DOI 10.17487/RFC6049, January 2011,
             <https://www.rfc-editor.org/info/rfc6049>.

  [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>.

  [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>.

  [RFC8029]  Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
             Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
             Switched (MPLS) Data-Plane Failures", RFC 8029,
             DOI 10.17487/RFC8029, March 2017,
             <https://www.rfc-editor.org/info/rfc8029>.

  [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
             Writing an IANA Considerations Section in RFCs", BCP 26,
             RFC 8126, DOI 10.17487/RFC8126, June 2017,
             <https://www.rfc-editor.org/info/rfc8126>.

  [RFC8762]  Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple
             Two-Way Active Measurement Protocol", RFC 8762,
             DOI 10.17487/RFC8762, March 2020,
             <https://www.rfc-editor.org/info/rfc8762>.

  [RFC8972]  Mirsky, G., Min, X., Nydell, H., Foote, R., Masputra, A.,
             and E. Ruffini, "Simple Two-Way Active Measurement
             Protocol Optional Extensions", RFC 8972,
             DOI 10.17487/RFC8972, January 2021,
             <https://www.rfc-editor.org/info/rfc8972>.

  [RFC9037]  Varga, B., Ed., Farkas, J., Malis, A., and S. Bryant,
             "Deterministic Networking (DetNet) Data Plane: MPLS over
             IEEE 802.1 Time-Sensitive Networking (TSN)", RFC 9037,
             DOI 10.17487/RFC9037, June 2021,
             <https://www.rfc-editor.org/info/rfc9037>.

  [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>.

Acknowledgments

  The authors extend their appreciation to Pascal Thubert for his
  insightful comments and productive discussion that helped to improve
  the document.  The authors are enormously grateful to János Farkas
  for his detailed comments and the inspiring discussion that made this
  document clearer and stronger.  The authors recognize helpful reviews
  and suggestions from Andrew Malis, David Black, Tianran Zhou, and
  Kiran Makhijani.  And special thanks to Ethan Grossman for his
  fantastic help in improving the document.

Authors' Addresses

  Greg Mirsky
  Ericsson
  Email: [email protected]


  Mach(Guoyi) Chen
  Huawei
  Email: [email protected]


  Balazs Varga
  Ericsson
  Budapest
  Magyar Tudosok krt. 11.
  1117
  Hungary
  Email: [email protected]